GF-8802

FURUNO Multi-GNSS Disciplined Oscillator Models GF-8801, GF-8802, GF-8803, GF-8804, GF-8805 Protocol Specifications (Document No. SE18-600-004-00) www.furuno.com GF-880X Protocol Specifications SE18-600-004-00 IMPORTANT NOTICE No part of this manual may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, for any purpose without the express written permission of the publisher, FURUNO ELECTRIC CO., LTD. FURUNO ELECTRIC CO., LTD. All rights reserved. All brand and product names are registered trademarks, trademarks or service marks of their respective holders. The following satellite systems are operated and controlled by the authorities of each government. GPS, SBAS (WAAS): USA GLONASS: Russia Galileo, SBAS (EGNOS): Europe QZSS, SBAS (MSAS): Japan SBAS (GAGAN): India FURUNO is not liable for any degradation while using these satellite systems. FURUNO cannot guarantee specifications if any of these systems experience degradation. Based on these conditions the user is expected to be familiar with these systems and is fully responsible for their use. This document describes the eSIP protocol specifications for the following products. ・GF-8801 ・GF-8802 ・GF-8803 ・GF-8804 ・GF-8805 Although this product is paying attention to compatibility with the past products, due to the correspondence to various additions of specifications, some actions may differ unavoidably. Regarding the specifications, the contents described in this document are set as true, and for items not described in this document, the actual operations of this product are set as true. For this product, if you need items compatible with past products, please consult us before mass-producing this product. We pay through attention about the software of this product. But, if perchance you found a bug or a trouble, please feel free to contact us directly. We will check it, and if it is a bug, we may send you a new version with a bug fix. If perchance we found a bug or a trouble, we may send you a new version after we contact you. When we send you the new version software, we may ask you to update software. Therefore, we strongly recommended being able to access to serial port of this product from outside of your product to make software update easy. In addition, we also strongly recommend connecting between serial port of this product and network to remote access and update software. In this product, FURUNO can ensure safe performance only the commands and the sentences which are written in this document or are written in the document for this product. Please do not use the commands of the others products, otherwise this product may have troubles and FURUNO may not support about the troubles. FURUNO may inform some internal commands for verification etc. In this case, please use the commands only for operation test and please do not use them for technical operation. FURUNO ELECTRIC CO., LTD. reserves the right to make changes to its products and specifications without notice. GF-880X Protocol Specifications SE18-600-004-00 Revision History Version 0 Changed contents Initial release. Date 2019.03.28 GF-880X Protocol Specifications SE18-600-004-00 Table of Contents 1 2 3 4 Outline ······················································································································ 1 Terms ························································································································ 1 Communication Specifications ··················································································· 10 Serial Data Output Timing ·························································································· 11 4.1 Output Timing of 1PPS and Serial Data ·········································································· 11 4.2 Notes on Sentence Output ···························································································· 11 5 NMEA Sentence Format ····························································································· 12 5.1 Standard Sentence ······································································································ 12 5.2 Proprietary Sentence ··································································································· 13 5.3 Talker ID ····················································································································· 14 5.4 Output Priority of Sentence and Default Output Sentence ················································ 15 6 Output Sentences ····································································································· 16 6.1 RMC – Recommended Minimum Navigation Information ·················································· 16 6.2 GNS – GNSS Fix Data ··································································································· 17 6.3 GGA – Global Positioning System Fix Data ····································································· 18 6.4 GLL – Geographic Position - Latitude/Longitude ····························································· 19 6.5 VTG – Course Over Ground and Ground Speed ······························································· 20 6.6 GSA – GNSS DOP and Active Satellites ·········································································· 21 6.7 ZDA – Time & Date ······································································································· 22 6.8 GSV – GNSS Satellites in View ······················································································ 23 6.9 QSM – Satellite Report for Disaster and Crisis Management (DC Report) Message ·············· 25 6.10 CRW (TPS1) – Time and Leap Second ············································································ 26 6.11 CRX (TPS2) – PPS Information ······················································································ 29 6.12 CRY (TPS3) – Position Mode & TRAIM ············································································ 31 6.13 CRZ (TPS4) – VCLK Frequency and Control ···································································· 34 6.14 CRG – QZSS L1S Disaster and Crisis Management Report Message·································· 40 6.15 CRJ – Detection Status of Jamming Signal ····································································· 41 6.16 CRP – High Resolution Current Position········································································· 42 6.17 CRQ – SAR / RLM Information Broadcasted by Galileo Satellites ······································ 43 6.18 ACK – Output the Command Reception Check ································································ 44 6.19 MSG – Event Driven Message························································································ 44 6.20 VERSION – Software Version ························································································ 45 6.21 FIXSESSION – Fix Session···························································································· 45 6.22 ANTSEL – Antenna Selecting ························································································ 46 7 Input Commands ······································································································ 47 7.1 API [GNSS] – Satellite System Configuration ·································································· 47 7.2 API [PPS] – PPS Setting ······························································································· 48 7.3 API [GCLK] – GCLK Frequency Setting ·········································································· 49 7.4 API [SURVEY] – Position Mode Setting··········································································· 50 7.5 API [RESTART] – Restart Command··············································································· 53 7.6 API [FLASHBACKUP] – Back up to FLASH ROM ····························································· 54 7.7 API [DEFLS] – Default Leap Second Setting ···································································· 55 7.8 API [TIMEZONE] – Local Zone Time Setting ···································································· 56 7.9 API [TIMEALIGN] – Time and PPS Alignment Setting ······················································· 58 7.10 API [TIME] – Time Setting ····························································································· 59 7.11 API [FIXMASK] – Positioning and Satellite Mask Setting··················································· 60 7.12 API [OCP] – Detailed Elevation and Azimuth Mask Setting ················································ 61 7.13 API [NLOSMASK] – NLOS Satellite Elimination Algorithm Setting ····································· 64 7.14 API [MODESET] – Frequency Mode Transition Condition Setting ······································ 66 7.15 API [PHASESKIP] – Phase Skip Setting ·········································································· 67 7.16 API [HOSET] – Holdover Setting ···················································································· 68 7.17 API [EXTSYNC] – External Synchronized Function Setting ··············································· 69 7.18 API [ANTSET] – Antenna Power Feed Setting ·································································· 70 7.19 API [ALMSET] – Alarm Output Setting ············································································ 70 7.20 API [CROUT] – CR Sentence Output Setting ··································································· 71 7.21 CFG [NMEAOUT] – Standard NMEA Output Setting·························································· 72 GF-880X Protocol Specifications SE18-600-004-00 7.22 CFG [UART1] – Serial Communication Port Setting ························································· 72 7.23 SYS [VERSION] – Software Version Request ··································································· 73 7.24 SYS [ANTSEL] – Antenna Input Setting ·········································································· 73 8 Backup of the Receiver Parameters (for BBRAM) ·························································· 74 9 Insertion of Leap Second ··························································································· 76 10 Instructions and Directions for Use ············································································· 77 11 FAQ ························································································································ 78 GF-880X Protocol Specifications SE18-600-004-00 1 Outline This document describes the serial communications interface protocol for the FURUNO Multi-GNSS Disciplined Oscillator (GNSSDO) which is GF-8801, GF-8802, GF-8803, GF-8804 and GF-8805 [*1]. The software version covered by this document is 4850-577-000 (ENP708A) or later. [*1] This document shows these GNSSDO as GF-880X. 2 Terms This chapter describes details of terms used in this document. Since it contains a lot of important information on the behavior of this product, we strongly recommend you to read it carefully. Terms Protocol Command Sentence Serial data eSIP National Marine Electronics Association (NMEA) ACK NACK Table 2.1 Terms Related to Communication Description It is a communication procedure for sending and receiving data using the communication port. In this document, the data sent to the product is called a command. In this document, the data received from the product is called a sentence. It is a generic name of the data itself to transmit and receive using the communication port. Although it may be described as output of serial data in this document, in that case it is synonymous with sentence. It is one of protocol format. It is the standard format output by our GNSS receiver. This document mainly describes details about the eSIP. In this document, ASCII and communication protocol of NMEA 0183 standard are called NMEA. The product outputs serial data conforming to NMEA0183 Ver. 4.10 established in June 2012. It means acknowledgement. When a command is input to the product, if the command is accepted as being appropriate, the product returns ACK as a response sentence. It means negative acknowledgement. When a command is input to the product, if the command is ignored as being inappropriate, the product returns NACK as a response sentence. If NACK is returned, please check whether the format of the transmitted command is appropriate and checksum is appropriate. 1 GF-880X Protocol Specifications SE18-600-004-00 Terms Ephemeris Table 2.2 Terms Related to Messages Broadcast by Satellites Description It is one of information that the satellite is broadcasting. Mainly satellite time and detailed orbit information of its satellite are broadcasted. It is information necessary for positioning, and it is repeatedly broadcast in short cycles. In case of GPS satellites, the ephemeris is broadcasted every 30 seconds. It is called HOT START especially in this product to start up with ephemeris information remaining in the receiver. Although the expiration date of the ephemeris it possesses depends on the type of satellite, but it is 1 to 4 hours since the last ephemeris was received. It is one of information that the satellite is broadcasting. Mainly various correction information, UTC parameters and rough orbit information of all satellites are broadcasted. In case of GPS satellites, the almanac is broadcasted at a cycle of 900 seconds. Therefore, it may take up to 900 seconds from GPS synchronization to UTC synchronization after initial positioning. Almanac It is called WARM START especially in this product to start with almanac information remaining in the receiver. If neither ephemeris nor almanac information remains in the receiver, it will start by COLD START. Interface Control Document (ICD) There is no expiration date for the almanac it possesses. It is a document defining the content and structure broadcasted by each satellite as a specification by the relevant division of the country that operates the satellites. This product is designed based on those ICD. The ICD referred to by this product is as follows. Satellite ICD IS-GPS-200 GPS Revision H,IRN003 28 July 2016 Navigation radio signal In bands L1, L2 GLONASS Version 5.1 2008 EUROPEAN GNSS(GALILEO) OPEN SERVICE SIGNAL-IN-SPACE Galileo Issue 1 revision 3 December 2016 IS-QZSS-PNT-002 QZSS L1C/A 29 January 2018 IS-QZSS-L1S-002 QZSS L1S 13 April 2018 ICD does not claim permanent specification definition, but ICD of the satellite may be updated in the future depending on the type of satellite, and a part of the broadcast content may be changed. Please note that this product does not guarantee including the changed part of those updated ICD. 2 GF-880X Protocol Specifications SE18-600-004-00 Terms GNSS (GNSS satellite) SBAS (Differential correction) SLAS correction information Satellite number Jamming signal Anti-Jamming Spoofing signal Table 2.3 Terms Related to Satellite and Satellite Signal Description GNSS stands for Global Navigation Satellite System. It may be described as a generic name of satellites such as GPS, GLONASS, Galileo, QZSS and SBAS. SBAS is a satellite transmitting correction information useful for positioning calculations. This correction information is called differential information, and correcting the positioning calculation process using this information is called differential correction. This product supports differential correction and this is done by default. It is possible to add SBAS itself as one satellite to the positioning calculation like GPS. However, experiments show that the positioning performance deteriorates when SBAS is added to the positioning calculation. Therefore, in this product, SBAS is set not to add to positioning calculation by default. In our experiment, the order of contributing to performance improvement by using SBAS is as follows: Use differential positioning only > Use differential positioning + SBAS positioning > Do not use SBAS. In addition, since SBAS alone cannot align parameters necessary for initial positioning, SBAS standalone positioning setting is prohibited in this product. It is correction information broadcasted from the QZSS L1S signal. It can be used when QZSS L1S signal is received. It is the number assigned to the satellite. In this product, the satellite number is assigned as follows. These satellite numbers are mainly used for GSA and GSV. (Please refer to the hardware specifications for satellite numbers that can be actually received.) Satellite GPS SBAS GLONASS QZSS L1C/A QZSS L1S Galileo MIN 01 33 65 93 83 01 MAX 32 51 96 99 89 36 Notes Same as PRN No Subtract 87 from PRN No Same as PRN No Subtract 100 from PRN No Subtract 100 from PRN No Same as PRN No When the satellite number is duplicated, the type of satellite can be distinguished by the GNSS system ID of GSA sentence or the talker ID of GSV sentence. It is a signal other than the satellite signal that is mixed in the frequency band of the satellite signal. Noises of other equipment may accidentally be mixed in, or intentional broadcasting by malicious persons may be mixed. If the jamming signal is received, it will be impossible to receive the frequency of the satellite signal, resulting in a poor positioning or undetectable state. Even if a jamming signal is mixed in, the receiver masks the signal as much as possible so that it can receive satellite signals normally. In this product, the Anti-Jamming function is operating by default, and it is possible to mask up to eight jamming signals. It is a signal generated by a malicious person mimicking the broadcast contents of GNSS satellite using what is similar to simulator. Reception of this signal may affect the position and time. This product has a function to detect and eliminate spoofing signal. For details, please refer to TPS3 sentence. 3 GF-880X Protocol Specifications SE18-600-004-00 Terms Leap second Table 2.4 Terms Related to Time Description It means one second that is inserted so that there is no gap in the difference between the rotation of the earth and the atomic clock that is the time reference. Normally, the leap second insertion is determined, announced, and broadcasted one to two months in advance. Insertion timing is January 1st or July 1st. The leap second has been inserted since 1972. However, considering that GPS and QZSS satellites are being operated starting from January 6, 1980, this product displays the leap second integrated value since January 6, 1980. This is consistent with the integrated value of leap second that the GPS, QZSS and Galileo satellite actually broadcast as a message. In this document, the integrated value of leap second may be referred to simply as leap second. It is time system broadcasted by GPS satellite. It is broadcasted as a continuous time that does not consider the leap second since the start of January 6, 1980. GPS time GPS satellites broadcast the week number (0 to 1023) and the week second (0 to 640799). The receiver converts to the current time by using them. In recent years the time difference between UTC time and GPS time is on the order of a few nanoseconds. However, there is no guarantee that this time difference will be kept for the future. The week number broadcasted by the GPS and QZSS satellite returns to 0 the next week of 1023. Therefore, if only these satellites are being received, it is known that there is a limit in the period during which the current time can be properly converted by a general GNSS receiver. In this document, the timing at which week number 1023 goes to 0 is called week number rollover. Week number rollover GLONASS time This product addresses to this week number rollover, and even if the broadcasted week number returns to 0 from 1023, the correct time can be displayed continuously. However, the time range that can be converted properly is still up to 1024 weeks. The range in which this product can display an appropriate time without backup is up to 23:59:59 on October 10, 2037. If the receiver starts and restarts without backup after then, the time before 1024 weeks may be displayed. In this case, you can display the correct time by setting the correct time with the command or by positioning with the GLONASS satellite or Galileo satellite. If the power is on continuously, the time update can be continued appropriately even if it exceeds the above date. It is time system broadcasted by GLONASS satellite. It is a time that always considered leap second, starting from January 1, 1996. Time parameters that can be uniquely converted until 2100 or later are broadcasted. By receiving the GLONASS satellite, it is possible to display the correct time without being conscious of week number rollover that was concerned with receiving only GPS and QZSS satellites. Also, because it includes leap seconds in the time system, by receiving the GLONASS satellite and other satellites at the same time, it is possible to immediately acquire the correct leap second without waiting for the reception of the UTC parameter. 4 GF-880X Protocol Specifications SE18-600-004-00 Terms Galileo time UTC time UTC parameter Default leap second Local Zone Time (LZT) Estimated accuracy Table 2.5 Terms Related to Time Description It is time system broadcasted by Galileo satellite. It starts from August 22, 1999. However, practically it is broadcasted as a continuous time that does not consider the leap second since January 6, 1980, so that each parameter matches the GPS and QZSS satellite. Time parameters that can be uniquely converted until February 19, 2078 are broadcasted. By receiving the Galileo satellite, it is possible to display the correct time until 2078 without being conscious of the week number rollover that was concerned with receiving only GPS and QZSS satellites. UTC stands for Coordinated Universal Time. It is always considered leap second and matches the time we usually use by considering the time difference of each country. UTC is set for each country by the atomic clock owned by each country, and it is slightly different on the nanosecond scale although it cannot see any difference in any country over integer seconds. For example, in case of the United States, the United States Naval Observatory prescribes the UTC time as UTC (USNO). Similarly, in case of Russia it is called UTC (SU). This product can select which UTC to synchronize by command. The default is synchronized to UTC (USNO). It is a parameter broadcasted by each satellite to convert the time system of each satellite to UTC time. Mainly it includes integrated value of leap second, leap second insertion timing and correction information of nanosecond scale. However, since the GLONASS satellite contains leap seconds in the time system, the accumulated value of the leap second is not broadcasted. The UTC parameters are generally included in navigation messages called almanac, and there is a gap in the broadcasting interval. This value is set to temporarily bring the sentence output time closer to the UTC time when the leap second information has not been acquired from the GPS satellite. This value can also be stored in FLASH ROM. By setting this properly in advance, it is possible to get the time information equivalent to the UTC time earlier from the sentence before acquiring the UTC parameter. Note that this setting only adjusts the display time before acquiring the correct leap second, and even if this value is incorrect it does not affect positioning calculation. Also, if leap second information can be obtained from the satellite at least once, it will be used with priority thereafter. It means time offset value from UTC time. By setting the LZT with the TIMEZONE command, you can obtain the time information with LZT added from the ZDA sentence. It shows how far the receiver's time may deviate from the synchronization target. The standard deviation (1 sigma) of the pseudorange of all satellites displayed in the GSA sentence is displayed in nanoseconds. In an open sky environment, this value will be lower. In poor environments such as indoors, this value will increase due to the influence of multipath satellites. Therefore, it can be used to judge whether the reception environment is good or bad. For explanation of pseudorange and multipath, please refer to the following. 5 GF-880X Protocol Specifications SE18-600-004-00 Terms Pulse Per Second (PPS) Table 2.6 Terms Related to PPS and Frequency Description Outputting one pulse per second is called 1PPS. It is the frequency output by the voltage controlled oscillator installed in this product. VCLK frequency GCLK frequency VCLK PPS Holdover Learning period (time) Cable delay RTC synchronization GPS synchronization UTC synchronization EPPS synchronization GNSS synchronization While receiving GNSS, a stable clock is provided by adjusting the frequency based on the time acquired from the GNSS satellite. In some environments that GNSS cannot receive, some products guarantee clock stability in free running state. Please refer to the item of holdover for details. It is a mechanism to generate arbitrary frequency by using the system clock of this product and built-in adder. By receiving the GNSS satellite, it is possible to output arbitrary frequency accurately. Since the frequency is generated using the adder, it is necessary to check in advance whether jitter and spurious included in the GCLK frequency are within the allowable range of the application to be used. It is PPS that the clock edge of the VCLK frequency and the timing of the pulse edge of PPS are synchronized. This product outputs this PPS. Note that the pulse edge of VCLK PPS is not synchronized with the GCLK frequency. It is a function to maintain the performance of 1PPS and frequency during satellite reception as much as possible while GNSS satellites cannot be received. Holdover performance varies depending on the product. For detailed specifications, please refer to the hardware specifications of the products. For holdover, it is necessary to continuously receive GNSS satellites for a predetermined period. This product estimates the frequency aging deterioration characteristics and frequency temperature characteristics of the oscillator during this period, and then automatically learns the optimum control at the time of the GNSS satellite interruption. In this document, the above period is called the learning period or learning time. In addition, it may be said that learning has been completed when the learning period is satisfied. When connecting the antenna and this product with a cable, a delay occurs in PPS according to the cable length. In this document, this delay is called cable delay. This delay can be corrected with the PPS command. RTC stands for Real Time Clock. It is sometimes described as RTC synchronization especially in this document to indicate that the PPS and frequency are in free-run state before receiving the satellite and confirming the time, or when GNSS interruption continues for more than a certain period of time. It is a state outputting the time, PPS and frequency in synchronization with the GPS time. This product transits to this state when GPS synchronization is set or UTC parameter is not acquired. It is a state outputting the time, PPS and frequency in synchronization with the UTC time. Which UTC to synchronize can be selected by a command. It is a state that the oscillator is synchronized with the signal input from the EPPS pin without using GNSS. It is paired with GNSS synchronization. It is a state to receive GNSS and synchronize the oscillator to the GNSS time. It is paired with EPPS synchronization. The default is GNSS synchronization. In case of GNSS synchronization, the synchronization target is further divided into GPS sync and UTC sync. 6 GF-880X Protocol Specifications SE18-600-004-00 Terms Frequency mode (Frequency control mode) WARMUP PULLIN COARSE LOCK FINE LOCK HOLDOVER OUT OF HOLDOVER Terms Battery Backup Random Access Memory (BBRAM) FLASH ROM (FLASH) Table 2.7 Terms Related to PPS and Frequency Description It mainly shows the stable state of the VCLK frequency. There are six kinds of frequency modes: WARMUP, PULLIN, COARSE LOCK, FINE LOCK, HOLDOVER, and OUT OF HOLDOVER. It is a state waiting for stabilization of the internal clock after turning on the power supply. It is a state that GNSS is received and in the middle of synchronizing the VCLK frequency and PPS with the synchronization target based on the time obtained from GNSS. It is a state that GNSS is received and the VCLK frequency and PPS are synchronized with the synchronization target based on the time obtained from GNSS. However, the synchronization accuracy is coarse than FINE LOCK. It is a state that GNSS is received and the VCLK frequency and PPS are synchronized with the synchronization target precisely based on the time obtained from GNSS. While in this state, this product learns for holdover. When GNSS cannot be received, if the learning for holdover is completed beforehand, the frequency mode transits to this mode. The frequency of the oscillator is automatically controlled in consideration of the frequency aging deterioration characteristics and the frequency temperature characteristics. A better frequency and PPS than the free-run state are provided. For product specifications in this state, please refer to the corresponding hardware specifications. It is a state that holdover has ended or GNSS cannot be received when the learning for holdover is not satisfied. In this mode, the output frequency and 1PPS of this product are out of specification. Table 2.8 Terms Related to Storage Area Description It is a storage area that can be used as a backup area only when backup current is applied to this product. Ephemeris data, almanac data, command setting values and so on are sequentially stored. The storage area is read at startup or at restart. You can erase the stored information by interrupting the application of backup current or sending a prescribed reset command to this product. It is a storage area using Flash ROM. By sending FLASHBACKUP command to this product, some settings can be saved at that timing. The storage area is read at startup or at restart. Once backed up to FLASH, it can be erased only when software update or FLASHBACKUP command is sent again. When settings related to the same item are stored in both BBRAM and FLASH, BBRAM setting takes precedence. At this time, if the data on the BBRAM side becomes invalid due to stoppage of backup power supply, FLASH data will be applied at the next start or restart. 7 GF-880X Protocol Specifications SE18-600-004-00 Terms Time Receiver Autonomous Integrity Monitoring (T-RAIM) Position mode Fixed position Estimated position (Position estimation) NAV mode (Navigation) TO mode (Time Only) SS mode (Self Survey) CSS mode (Continuous Self Survey) Table 2.9 Terms Related to Positioning Processing Description It is a mechanism to identify and eliminate satellites that may have a bad influence on the positioning calculation by combining and principle of majority when the number of satellites in use is larger than the minimum number of satellites required for positioning. With this function, the results of the positioning calculation are further improved. The maximum number of satellites eliminated by this function is 3. Generally, the GNSS receiver calculates parameters such as latitude, longitude, height, speed, direction and time by receiving four or more satellites. On the other hand, if it is known in advance to use the receiver at a fixed position, by preparing the latitude, longitude and height in advance, the time can be calculated with only one or more satellite reception, precise 1PPS and frequency can be maintained. There are four kinds of position mode: NAV mode, TO mode, SS mode and CSS mode. The position of the fixed point to be set when using the TO mode may be described like this in this document. In the process of calculating the fixed position, the position that the position accuracy is not sufficiently converged yet may be described as the estimated position in this document. In addition, the process of calculating the estimated position may be described to as position estimation. Latitude, longitude, height, speed, direction and time are calculated every second. Since position, speed and direction are updated every second, it is suitable for mobile use. In order to perform positioning in this mode, it is required to receive four or more satellites except SBAS. By using the fixed position, only time is calculated every second. Compared to NAV mode, it is excellent in time stability and it is suitable for use at fixed points. In order to perform positioning in this mode, it is required to receive one or more satellites except SBAS. Latitude, longitude, height and time are calculated every second. This mode is suitable when you want to use the TO mode but you do not know the position of the fixed point. This mode calculates the position of the fixed point with high accuracy based on the position information obtained during a fixed period (default 24 hours), and after calculating it transits to the TO mode automatically. In order to calculate the fixed position in this mode, it is required to receive four or more satellites except SBAS. However, even if it is less than four satellites, if there is more than one satellite, processing equivalent to the TO mode is performed using the information of the fixed position calculated so far, the time is appropriately updated, precise 1PPS and frequency can be maintained. Although processing similar to the SS mode is performed, while the SS mode discards the calculation process of the fixed position when the power is off, the CSS mode backs up the calculation process to the BBRAM. Therefore, the calculation of the fixed position is continued using the calculation process before turning off the power even at the next startup. 8 GF-880X Protocol Specifications SE18-600-004-00 Terms Positioning calculation Pseudorange Doppler frequency Line Of Sight (LOS) Table 2.10 Terms Related to Positioning Processing Description It means that the GNSS receiver calculates various kinds of information such as satellite and receiver position, speed, time and receiver azimuth based on information from the satellites. It is one of the information used by the GNSS receiver at positioning calculation. It is the result of calculating the distance between the satellite and the receiver. It is one of the information used by the GNSS receiver at positioning calculation. It is the result of calculating the frequency of the signal received from the satellite. It means that a signal from a satellite is coming directly to the antenna connected to this product. It is synonymous with the state where there is no shielding between the satellite and the antenna, and the satellite in such state is called LOS satellite especially in this document. If many LOS satellites can be received, not only stable signal level can be expected but also position accuracy and time accuracy can be obtained satisfactorily. In contrast to LOS satellites, it means that there is some sort of obstruction between a satellite and the antenna. Although satellites whose signals are completely discontinued and determined as satellite discontinuities are also strictly included in NLOS satellites, in this document they are simply described as satellite interruption and shall not be described as NLOS satellites. Non Line Of Sight (NLOS) In this document, we define the satellite as the NLOS satellite, which cannot receive the direct signal from the satellite but only weak signals that arrive bypassing by reflecting to the surrounding building. Signals that are reflected to surrounding buildings and are received bypassing are particularly called multipath. It is known that using this multipath signal tends to degrade the positioning accuracy because errors are generated in the calculation of pseudorange and Doppler frequency. Determining appropriately what satellite is the NLOS satellite and appropriately masking them and performing positioning with only the LOS satellite leads to an improvement in positioning accuracy. 9 GF-880X Protocol Specifications SE18-600-004-00 3 Communication Specifications Signal Lines used: Flow Control: System: Speed: Start Bit: Data Length: Stop Bit: Parity Bit: Data Output Interval: Character Codes used: TXD, RXD None Full Duplex Asynchronous 38400 bps [*1] 1 bit 8 bits 1 bit None 1 second NMEA-0183 Ver.4.10 data based ASCII code [*2] Protocol: Input data NMEA Proprietary sentence Output data NMEA Standard sentence NMEA Proprietary sentence Notes: [*1] Baud rate It can be changed by a command. Please see UART1 command page for details. For the relationship between UART baud rate and error, please refer to the hardware specifications. [*2] NMEA format “NMEA 0183 STANDARD FOR INTERFACING MARINE ELECTRONIC DEVICES Version 4.10” (NATIONAL MARINE ELECTRONICS ASSOCIATION, June, 2012) 10 GF-880X Protocol Specifications SE18-600-004-00 4 Serial Data Output Timing 4.1 Output Timing of 1PPS and Serial Data The output timing of sentence (serial data) is synchronized with 1PPS output from PPS port when the frequency mode is COARSE LOCK, FINE LOCK and HOLDOVER. The sentence output begins in the range from 25 ms to 75 ms after the rising of 1PPS. The time of the sentence indicates the time of the next 1PPS output timing. However, information and status related to positioning other than time information are generated based on the positioning results one second before. Time = t Time = t + 1 Time = t + 2 Reference Time 1PPS Serial data Time = t + 1 Time = t + 2 25 - 75 ms 25 - 75 ms 25 - 75 ms Figure 4.1 Relation between 1PPS, Serial Data and Output Time 4.2 Notes on Sentence Output This product limits the amount of sentences that can be outputted per second in order to maintain the output relation between 1PPS and sentence. Sentence output per second is set to 90% of the number of bytes that can be output at the current baud rate. Specifically, it is defined by the following calculation formula. Maximum amount that can be output per second [Byte] = Current baud rate [bps] / 10 [Bit] *0.9 Therefore, when the baud rate is 38400 bps, it is possible to output up to 3456 bytes, but if you set it beyond that, the sentence after the line considered to exceed it will be discarded without being output. When outputting a large number of sentences, it is recommended to change to a higher baud rate by UART1 command. 11 GF-880X Protocol Specifications SE18-600-004-00 5 NMEA Sentence Format 5.1 Standard Sentence Format: $ , ・・・ * 5 bytes Field $ Description Start-of Sentence marker 5-byte fixed length. First 2 bytes represent a talker ID, and the remaining 3 bytes represent the sentence data type. The relevant talker IDs are GP for GPS, GN for GNSS, GL for GLONASS and GA for Galileo. In this document, the talker ID is expressed as "XX" indicating a wild card. Variable or fixed-length fields preceded by delimiter “,” (comma). Comma(s) are required even when valid field data is not available i.e. null fields. Ex. “,,,,,” * In a numeric field with fixed field length, fill unused leading digits with zeroes. 8 bits data between “$” and “*” (excluding “$” and “*”) are XORed, and the resultant value is converted to 2 bytes of hexadecimal letters. Note that two hexadecimal letters must be preceded by “*”, and delimiter “,” is not required before *. All output sentences have checksum. For input sentences, the resultant value is checked and if it is not correct, the sentence is treated invalid. End-of-Sentence marker 12 GF-880X Protocol Specifications SE18-600-004-00 5.2 Proprietary Sentence Format: $ P 3 bytes , * * 3 bytes Field $ P ・・・ Description Start-of Sentence marker Proprietary sentence identifier 3-byte fixed length. GF-880X’s maker ID is “ERD” meaning eRide. Indicates the type of sentence. Variable or fixed-length fields preceded by delimiter “,” (comma). (Layout is maker-definable.) The fields inside [ ] are optional fields. 8 bits data between “$” and “*” (excluding “$” and “*”) are XORed, and the resultant value is converted to 2 bytes of hexadecimal letters. Note that two hexadecimal letters must be preceded by “*”, and delimiter “,” is not required before *. All output sentences have checksum. For input sentences, the resultant value is checked and if it is not correct, the sentence is treated invalid. End-of-Sentence marker 13 GF-880X Protocol Specifications SE18-600-004-00 5.3 Talker ID The talker ID displayed in the standard NMEA format changes as shown in Table 5.1, depending on the type of satellite being received and the talker ID field of the GNSS command. In this chapter, in the following chapters, the talker ID part is expressed as "XX" indicating a wild card. Table 5.1 Talker ID Displayed in Standard NMEA Format Talker ID setting Standard NMEA AUTO GN LEGACYGP RMC GNS GGA GN GLL GN/GP/GL/GA [*1] GP [*2] VTG ZDA GSA GN/GP/GL/GA [*1] GSV GP/GL/GA [*3] GP/GL/GA [*4] [*1] GN/GP/GL/GA switches according to the type of satellite used in positioning as follows. GN: Multi satellite system is available [*5], or no position fix. GP: Only GPS/QZSS/SBAS is used in position fix. GL: Only GLONASS is used in position fix. GA: Only Galileo is used in position fix. [*2] Even if it is set to use GLONASS or Galileo, and even if it is actually received, GSA and GSV will be displayed only in GP, and GSA / GSV information of GLONASS and Galileo will not be displayed. However, these satellites are not actually displayed, they are actually counted by the number of positioning satellites of GNS and GGA, and used in positioning calculations, various status calculations and displays. [*3] GP/GL/GA switches according to the type of satellite used in positioning as follows. GP is displayed while no positioning fix, receiving GPS/QZSS/SBAS, or receiving multi satellite system [*5]. GL is displayed while no positioning fix, receiving GLONASS, or receiving multi satellite system [*5]. GA is displayed while no positioning fix, receiving Galileo, or receiving multi satellite system [*5]. [*4] The GPGSV, GLGSV, and GAGSV sentences are always output to maintain the display form of the sentence even if it is no position fix or it cannot receive the satellite corresponding to the talker ID. [*5] The multi satellite system means a state that two or more groups are received from the combination of groups "GPS/QZSS/SBAS", "GLONASS", and "Galileo". Therefore, for example, even if GPS and QZSS are received, only GPGSV will be displayed as it is only receiving "GPS/QZSS/SBAS" group. Meanwhile, for example, when GPS and GLONASS are received, GAGSV is also displayed even if Galileo is not received because it satisfies the condition that it is receiving multiple kinds of satellites. 14 GF-880X Protocol Specifications SE18-600-004-00 5.4 Output Priority of Sentence and Default Output Sentence Sentences are output in the order shown in Table 5.2. Table 5.2 also shows the sentences that are output by default. They are output every second. Sentence output switching is possible with the CROUT command and the NMEAOUT command. Table 5.2 Output Priority of Sentence and Default Output Sentence Output priority Sentence Default output Setting command RMC ● GNS ● GGA GLL VTG NMEAOUT GSA ● High ZDA ● GSV ● QSM CRG CRJ CRP Low CRQ CROUT CRW(TPS1) ● CRX(TPS2) ● CRY(TPS3) ● CRZ(TPS4) ● QUERY Each command 15 GF-880X Protocol Specifications SE18-600-004-00 6 Output Sentences This chapter describes details of sentences output from GF-880X. There are unsupported fields in the output sentences. This document shows these fields as “NULL”. These fields are null fields. 6.1 RMC – Recommended Minimum Navigation Information Format: $XXRMC , hhmmss.sss , a , ddmm.mmmm , a , dddmm.mmmm , a , x.xx , 1 2 3 4 5 x.xx , ddmmyy , 8 9 Field Data Range Default 1 Time 000000.000 to 235960.000 - 2 Status A, V V 3 Latitude 0000.0000 to 9000.0000 ALL 0 4 Latitude direction N, S N 5 Longitude 00000.0000 to 18000.0000 ALL 0 E, W E - 0.00 , 10 , 11 *hh 13 ddd: [degree], mm.mmmm: [minute] True course 0.00 to 359.99 0.00 9 Date 010100 to 311299 - NULL NULL Always NULL NULL NULL Always NULL 11 12 V "N" (North) or "S" (South) 8 Magnetic declination Magnetic direction , dd: [degree], mm.mmmm: [minute] 7 10 a 7 Description It is output at RTC, GPS, UTC time according to positioning status, synchronization setting status, parameter acquisition status and so on. 60 seconds is displayed only when the leap is inserted. A: Data valid V: Data invalid Longitude direction Speed 6 6 "E" (East) or "W" (West) [knot] [degree] Variable length dd: [day], mm: [month], yy: [year] (last two digits) 12 Positioning mode A, D, N N A: GNSS fix D: Differential GNSS fix N: No position fix 13 Navigation status V V Always “V” Example: $GNRMC,012344.000,A,3442.8266,N,13520.1233,E,0.00,0.00,191132,,,D,V*0B Time: 01:23:44.000 Data valid 34 deg 42.8266 min N 135 deg 20.1233 min E True Course: 0.0 degrees Date: 19th November, 2032 Differential GNSS fix 16 Speed: 0.0 knots GF-880X Protocol Specifications SE18-600-004-00 6.2 GNS – GNSS Fix Data Format: $XXGNS , hhmmss.sss , ddmm.mmmm , a , dddmm.mmmm , a , ccc , xx , 1 2 3 x.x , 8 x.x , 9 Field Data Range Default 1 Time 000000.000 to 235960.000 - 2 Latitude 0000.0000 to 9000.0000 ALL 0 3 Latitude direction N, S N 4 Longitude 00000.0000 to 18000.0000 ALL 0 5 Longitude direction E, W E 6 Positioning status NNN to DDD (A,D,N) NNN 7 Number of satellites in use 00 to 32 00 8 HDOP 0.0 to 50.0 or NULL NULL 9 Sea-level altitude - -18.0 10 Geoidal height - 18.0 11 12 DGPS time DGPS number Navigation status NULL NULL NULL NULL V V 13 4 x.x 5 , 10 6 , 11 , 12 7 V *hh 13 Description It is output at RTC, GPS, UTC time according to positioning status, synchronization setting status, parameter acquisition status and so on. 60 seconds is displayed only when the leap is inserted. Latitude dd: [degree], mm.mmmm: [minute] "N" (North) or "S" (South) Longitude ddd: [degree], mm.mmmm: [minute] "E" (East) or "W" (West) Positioning status for each satellite system (GPS, GLONASS, Galileo) A: GNSS fix D: Differential GNSS fix N: No position fix Number of satellites in use Horizontal dilution of precision (HDOP) Variable length A null field is output while positioning is interrupted. [meter] Variable length [meter] Variable length Always NULL Always NULL Always “V” Example: $GNGNS,004457.000,3442.8266,N,13520.1235,E,DDN,22,0.5,40.6,36.7,,,V*60 Time: 00:44:57.000 34 deg 42.8266 min N 135 deg 20.1235 min E Status: [GPS: Differential GNSS fix, GLONASS: Differential GNSS fix, Galileo: No position fix] Number of satellites: 22 satellites HDOP: 0.5 Altitude: 40.6 meters high Geoidal height: 36.7 meters high Navigation status indicator: Not valid 17 GF-880X Protocol Specifications SE18-600-004-00 6.3 GGA – Global Positioning System Fix Data Format: $XXGGA , hhmmss.sss , ddmm.mmmm , a , dddmm.mmmm , a , x , xx , 1 2 x.x 8 3 , x.x , 9 4 M 10 , x.x 5 , 11 M 12 , 13 6 7 , *hh 14 Field Data Range Default 1 Time 000000.000 to 235960.000 - 2 Latitude 0000.0000 to 9000.0000 ALL 0 3 Latitude direction N, S N 4 Longitude 00000.0000 to 18000.0000 ALL 0 5 Longitude direction E, W E "E" (East) or "W" (West) 6 Positioning status 0 to 2 0 1: GNSS fix 2: Differential GNSS fix 0: No position fix 7 Number of satellites in use 00 to 12 00 Number of satellites in use [*1] 8 HDOP 0.0 to 50.0, or NULL NULL - -18.0 M M - 18.0 M NULL M NULL Horizontal dilution of precision (HDOP) Variable length A null field is output while positioning is interrupted. [meter] Variable length Units of altitude, meters [meter] Variable length Units of Geoidal height, meters Always NULL NULL NULL Always NULL 9 10 11 12 13 14 Sea-level altitude Unit Geoidal height M DGPS time DGPS number Description It is output at RTC, GPS, UTC time according to positioning status, synchronization setting status, parameter acquisition status and so on. 60 seconds is displayed only when the leap is inserted. Latitude dd: [degree], mm.mmmm: [minute] "N" (North) or "S" (South) Longitude ddd: [degree], mm.mmmm: [minute] Example: $GPGGA,025411.516,3442.8146,N,13520.1090,E,1,11,0.8,24.0,M,36.7,M,,*66 Time: 02:54:11.516 34 deg 42.8146 min N 135 deg 20.1090 min E Status: GNSS fix Number of satellites: 11 satellites HDOP: 0.8 Altitude: 24.0 meters high Geoidal height: 36.7 meters high [*1] GPS, SBAS, QZSS only. GLONASS and Galileo are not counted. The upper limit is 12. 18 GF-880X Protocol Specifications SE18-600-004-00 6.4 GLL – Geographic Position - Latitude/Longitude Format: $XXGLL , ddmm.mmmm , a , dddmm.mmmm , a , hhmmss.sss , a , a 1 Field Data 1 Latitude 2 2 3 Range 0000.0000 to 9000.0000 Default Latitude direction N, S N 3 Longitude 00000.0000 to 18000.0000 ALL 0 4 Longitude direction E, W E 5 Time 000000.000 to 235960.000 - 6 Status A, V V 7 Positioning mode A, D, N N ALL 0 4 5 6 *hh 7 Description Latitude dd: [degree], mm.mmmm: [minute] "N" (North) or "S" (South) Longitude ddd: [degree], mm.mmmm: [minute] "E" (East) or "W" (West) It is output at RTC, GPS, UTC time according to positioning status, synchronization setting status, parameter acquisition status and so on. 60 seconds is displayed only when the leap is inserted. A: Data valid V: Data invalid A: GNSS fix D: Differential GNSS fix N: No position fix Example: $GPGLL,3442.8146,N,13520.1090,E,025411.516,A,A*5F 34 deg 42.8146 min N 135 deg 20.1090 min E Time: 02:54:11.516 Mode: GNSS fix 19 Status: Data valid GF-880X Protocol Specifications SE18-600-004-00 6.5 VTG – Course Over Ground and Ground Speed Format: $XXVTG , x.x , 1 T 2 , , 3 M , x.xx , N , x.xx , K , a 4 5 6 7 8 9 Field Data Range Default 1 True course 0.00 to 359.99 0.00 2 3 4 5 6 7 8 Unit Magnetic direction Unit Speed Unit Speed Unit T NULL M N K T NULL M 0.00 N 0.00 K 9 Positioning mode A, D, N N Example: $GNVTG,0.00,T,,M,0.00,N,0.00,K,D*26 True Course: 0.00 degree Speed: 0.00 knot, 0.00 km/h 20 *hh Description [degree] Variable length Unit of true course, "T" (True) Always NULL "M" (Magnetic direction) Speed [knot] "N" (knots) Speed [km/h] "K" (Kilo meters/ Hour) A: GNSS fix D: Differential GNSS fix N: No position fix Mode: Differential GNSS fix GF-880X Protocol Specifications SE18-600-004-00 6.6 GSA – GNSS DOP and Active Satellites Format: $XXGSA , A , a , xx , 1 Field 1 2 Data Operational mode 3 ・・・ , xx , x.x 4-13 14 15 , x.x , 16 x.x 17 , x 18 Range Default A A 2D/3D auto-switching mode 1: No fix 2: 2D fix 3: 3D fix 2 Positioning mode 1~3 1 3-14 Satellite numbers used in positioning 01 to 99 NULL 15 PDOP 16 HDOP 17 VDOP 18 GNSS System ID 0.0 to 50.0, or NULL 0.0 to 50.0, or NULL 0.0 to 50.0, or NULL 1 to 3 NULL NULL NULL - *hh Description If it is less than 12 satellites, it is filled with NULL. [*1] Variable length A null field is output unless 3D-positioning is performed. Variable length A null field is output while positioning is interrupted. Variable length A null field is output unless 3D-positioning is performed. It shows which satellite information this GSA sentence is displaying. 1: GPS (involve SBAS and QZSS) 2: GLONASS 3: Galileo Example: $GNGSA,A,3,09,15,26,05,24,21,08,02,29,28,18,10,0.8,0.5,0.5,1*33 $GNGSA,A,3,79,69,68,84,85,80,70,83,,,,,0.8,0.5,0.5,2*30 Position fix mode: 3D fix PDOP: 0.8 HDOP: 0.5 VDOP: 0.5 Satellite used [GPS]: 09, 15, 26, 05, 24, 21, 08, 02, 29, 28, 18, 10 Satellite used [GLONASS]: 79, 69, 68, 84, 85, 80, 70, 83 [*1] Satellite numbers used in positioning Please use the GNSS system ID in the GSA sentence to identify which satellite the satellite number to be used belongs to. For example, if 01 is displayed in the satellite number of the GSA sentence and the GNSS system ID is 1, it means that it is No.1 satellite of GPS. If the GNSS system ID is 3, it means that it is No.1 satellite of Galileo. For the convenience of outputting the satellite number to be used in correspondence with the GNSS system ID, the GSA may display up to three lines; one line for GPS/QZSS/SBAS, one line for GLONASS, and one line for Galileo. When multiple lines are displayed, it is displayed in the order of GPS/QZSS/SBAS > GLONASS > Galileo. A GSA with GNSS system ID of 1 takes precedence over GPS > QZSS > SBAS. Since this GSA sentence is compliant with NMEA ver. 4.10 established in June 2012, up to 12 satellite numbers can be displayed on one line of GSA. Therefore, even if more than 13 satellites are used, only 12 satellites will be displayed. However, if you wish to cancel this restriction and display more satellite numbers to be used, you can display it by entering the following EXTENDGSA command. $PERDAPI,EXTENDGSA,num*hh num: Number of satellites to be display (Range: 12 to 16, Default: 12) For example, if the number of satellites to be displayed is set to 16 by using this command, the field of satellite number will be extended from “3 to 14” to “3 to 18”. The fields of PDOP, HDOP, VDOP are shifted behind. For the satellite number, please also refer to corresponding items in Chapter 2. 21 GF-880X Protocol Specifications SE18-600-004-00 6.7 ZDA – Time & Date Format: $XXZDA , hhmmss.sss , xx , xx , 1 2 xxxx 3 4 Field Data Range Default 1 Time 000000.000 to 235960.000 - 2 3 4 Day Month Year Local zone time [hour] Local zone time [minute] 01 to 31 01 to 12 1999 to 2099 - -23 to +23 +00 00 to 59 00 5 6 , xxx , xx 5 *hh 6 Description It is output at RTC, GPS, UTC time according to positioning status, synchronization setting status, parameter acquisition status and so on. 60 seconds is displayed only when the leap is inserted. When LZT is set, time will be displayed after adding it. When LZT is set, it will be displayed after adding LZT. When LZT is set, it will be displayed after adding LZT. When LZT is set, it will be displayed after adding LZT. The LZT value set by the TIMEZONE command is displayed. The unit is hour. The LZT value set by the TIMEZONE command is displayed. The unit is minute. Example: $GPZDA,014811.000,13,09,2021,+09,00*73 Time: 01:48:11 13th September, 2021 Local zone time: +9 hours 22 GF-880X Protocol Specifications SE18-600-004-00 6.8 GSV – GNSS Satellites in View Format: $XXGSV , x , x , xx , xx , xx , xxx , xx , xx , xx , xxx , xx , 1 Field 2 3 7 8 9 10 12 20 13 20 Signal ID 3 6 h 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2 5 xx , xx , xxx , xx , xx , xx , xxx , xx , Data Total number of messages Message number Number of satellites in line-of-sight Satellite number Elevation Azimuth C/N0 Satellite number Elevation Azimuth C/N0 Satellite number Elevation Azimuth C/N0 Satellite number Elevation Azimuth C/N0 1 4 14 15 16 17 18 19 11 *hh Range Default Description 1 to 5 1 Total number of messages per talker ID 1 to 5 1 Message number per talker ID 00 to 16 0 Number of satellites in line-of-sight per talker ID 01 to 99 00 to 90 000 to 359 00 to 69 01 to 99 00 to 90 000 to 359 00 to 69 01 to 99 00 to 90 000 to 359 00 to 69 01 to 99 00 to 90 000 to 359 00 to 69 NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL 1 or 7 - 1st satellite number 1st satellite elevation angle [degree] 1st satellite azimuth angle [degree] 1st satellite C/N0 [dB-Hz] 2nd satellite details Output in the same format as the first one. 3rd satellite details Output in the same format as the first one. 4th satellite details Output in the same format as the first one. 1: GPGSV or GLGSV 7: GAGSV Example: $GPGSV,4,1,14,15,67,319,52,09,63,068,53,26,45,039,50,05,44,104,49,1*6E $GPGSV,4,2,14,24,42,196,47,21,34,302,46,18,12,305,43,28,11,067,41,1*68 $GPGSV,4,3,14,08,07,035,38,29,04,237,39,02,02,161,40,50,47,163,44,1*67 $GPGSV,4,4,14,42,48,171,44,93,65,191,48,,,,,,,,,1*60 $GLGSV,3,1,09,79,66,099,50,69,55,019,53,80,33,176,46,68,28,088,45,1*76 $GLGSV,3,2,09,70,25,315,46,78,24,031,42,85,18,293,44,84,16,246,41,1*7A $GLGSV,3,3,09,86,02,338,,,,,,,,,,,,,,1*45 Not fixed [Note] The GSV sentence outputs up to four satellite information per line. More than four satellite information is output to the second and subsequent messages. Conversely, if less than a multiple of 4 or there are items that are not fixed in the satellite information, the item is NULL. The satellite information of GPS/QZSS/SBAS is GPGSV, the satellite information of GLONASS is GLGSV, and the satellite information of Galileo is output with GAGSV. The output order is GPGSV > GLGSV > GAGSV. However, there are GSVs that are hidden depending on GNSS command setting and reception status. For details, see about talker ID in Section 5.3. In the GSV of the same talker ID, after satellite position calculation, in principle, satellites are displayed in order of elevation angle. However, in the case of GPGSV, priority is given to GPS, QZSS and SBAS. In other words, 23 GF-880X Protocol Specifications SE18-600-004-00 the display order is as follows: GPS high elevation angle > GPS low elevation angle > QZSS high elevation angle > QZSS low elevation angle > SBAS high elevation angle > SBAS low elevation angle. However, depending on the relation of search, and before satellite position calculation, that is not the limit. When both QZSS L1C/A and QZSS L1S are used, the output order is QZSS L1S > QZSS L1C/A. In case of setting to receive SBAS, the satellite number of SBAS may change gradually until SBAS first fix. This shows the process of searching SBAS and will be resolved after receiving SBAS. Also, until the SBAS position is calculated, 0 may be output temporarily in the elevation angle and azimuth fields of the SBAS, but this will also be resolved after receiving the SBAS. For the satellite number, please also refer to corresponding items in Chapter 2. 24 GF-880X Protocol Specifications SE18-600-004-00 6.9 QSM – Satellite Report for Disaster and Crisis Management (DC Report) Message QSM sentence is not a protocol of NMEA 4.1 support, but it is the output format recommended by NEC operating and managing QZSS satellite to output DC report message. The output of DC report is also supported by CRG sentence. Format: $QZQSM , Satellite ID , DC Report MSG *hh 1 Field 1 2 Data Satellite ID DC Report MSG 2 Range 55, 56, 57, 58, 61 63 Bytes (HEX) Default - Description Satellite number that received the DC report [*1] DC report [*2] [*1] The satellite number is the lower 6 BIT in decimal notation of the 8 BIT which expresses the PRN number of L1S in binary number. In other words, 55 means 183, 56 means 184, 57 means 185, 58 means 186, 61 means 189. [*2] In this field, "00" is added to the last 2 BIT of the 250 BIT DC report message and it is displayed with 252 BIT (63 Bytes). Each BIT is represented by HEX and takes a range from 0 to F. [Restrictions] In order to properly output the DC report in this field, it is necessary to be set to receive the QZSS L1S signal with the GNSS command. This sentence will not be output unless it is set to receive QZSS L1S signal. This sentence outputs the information obtained by receiving the QZSS L1S signal as it is. The content of the DC report message needs to be interpreted by the host based on the user interface specification of the Cabinet Office. Please be aware that depending on the timing of message decoding, two different messages may be output from the same satellite in one second. Example: $QZQSM,55,53AC12345……9ABCDEFC*1F DC report “53AC12345……9ABCDEFC” is received. 25 GF-880X Protocol Specifications SE18-600-004-00 6.10 CRW (TPS1) – Time and Leap Second Format: $PERDCRW , TPS1 , Date & Time , Time status , Update date , Present LS , 1 2 3 4 Future LS , PPS status , 6 7 Field 1 Data TPS1 Range - Default - 2 Date & Time (14 bytes) - 3 Time status 0 to 2 (1 byte) 0 4 Update date (14 bytes) 5 Present LS 6 Future LS -99 to +99 (3 bytes) -99 to +99 (3 bytes) - Drift 5 , Temperature *hh 8 Description Command name Present date and time year, month, day, hour, minute, second It is output at RTC, GPS, UTC time according to positioning status, synchronization setting status, parameter acquisition status and so on. 60 seconds is displayed only when the leap is inserted. Present time status of output sentence [*1] 0: Before time fix 1: Leap second unknown or leap second ignored 2: Leap second fix Leap second update schedule year, month, day, hour, minute, second It is filled with 0 when UTC parameter has not been received or when there is no schedule for leap second insertion even if it is received. It is calculated based on satellite broadcast contents. Therefore, the update date may remain displayed for a while after the leap second insertion until the satellite broadcast content changes. +18 Present leap second [*2] +00 Future leap second [*3] 7 PPS status 0 to 5 (1 byte) 0 8 Drift (10byte) - 9 Temperature (5byte) - 9 Present PPS is synced with the follow. [*4] 0: RTC 1: GPS 2: UTC (USNO) 3: UTC (SU) 4: UTC (EU) 5: UTC (NICT) Clock drift [ppb] [*5] The ambient temperature is displayed as 100 times the value of [°C]. Example: $PERDCRW,TPS1,20120303062722,2,20120701000000,+15,+16,2,+00002.910,+4312*29 Present time: 2012/03/03 06:27:22 Present time status: UTC (leap second fix) Leap second update date: 2012/7/1 00:00:00 Present leap second: +15 Future leap second: +16 PPS status: UTC (USNO) Clock drift: An offset of + 2.910 [ppb] is being detected for the built-in 26 MHz TCXO. Ambient temperature: +43.12 [°C] 26 GF-880X Protocol Specifications SE18-600-004-00 [*1] Time status Time status indicates the synchronization status of the time displayed in each sentence (including sentences other than TPS1). It is useful for determining whether the sentence's output time is after the time information is obtained from the satellite or contains an appropriate leap second. I. 0: Before time fix The display time is incorrect since the time is not obtained from the satellites. II. 1: Leap second unknown or leap second ignored (1) "Ignore leap second" is selected with the TIMEALIGN command. Time is displayed as GPS time. Leap second is not used. (2) “Use leap second” is selected with the TIMEALIGN command. Leap second has not been received from the satellites, and the time is displayed with the default leap second. III. 2: Leap second fix Time is displayed as UTC time including the leap second. [*2] Present leap second This field shows the default leap second until information on leap second is obtained from the satellites. Also, after the leap second information is obtained from the satellite, the information from the satellite is displayed as it is. Therefore, when a leap second is inserted, even after insertion, the update date and the present LS fields are not updated immediately, but are updated at the timing when the satellite actually updates the broadcast contents (Usually within a few days after leap second insertion). [*3] Future leap second Like the AC field, this field also displays the information from the satellite as it is. Also, 0 is filled before UTC parameter is received. Even if there is no schedule of leap second insertion, 0 may be displayed. [*4] PPS status PPS status indicates the synchronization status of PPS. It is useful for determining whether PPS is output at the specified synchronization timing. It is different from the time status in that it shows the nanosecond scale synchronization state below the integer seconds. I. 0: RTC The output PPS is not yet synchronized to anything. Even when the PPS status is GPS synchronization or UTC synchronization, if satellite interruption occurs and it is determined that PPS is largely out of synchronization target, RTC synchronization is displayed until re-positioning and time fix. Even when the frequency mode is WARM UP, PULLIN or OUT OF HOLDOVER, it will be RTC synchronization. II. 1: GPS (1) “GPS synchronization” is selected with the TIMEALIGN command. PPS is synchronized with GPS time. (2) “UTC synchronization” is selected with the TIMEALIGN command. The specified UTC parameter has not been received yet, it is provisionally synchronized with the GPS time. III. 2~5: UTC It is synchronized with the UTC time set by the TIMEALIGN command. (The corresponding UTC parameter has been received.) 27 GF-880X Protocol Specifications SE18-600-004-00 [*5] Clock drift The Drift field indicates the frequency deviation with respect to TCXO with a nominal frequency of 26 MHz built in this product by ppb value. This is obtained from the positioning calculation, and is generally called clock drift. There are two causes of clock drift fluctuation: TCXO origin (TCXO aging and temperature variation characteristics) and GNSS origin (positioning calculation error using GNSS signal). Since this product synchronizes 1PPS to the synchronization target based on this clock drift, this value and 1PPS output value correlate. By observing this value, it is possible to estimate fluctuation of 1PPS. For example, when there is no temperature fluctuation around this product, the clock drift caused by TCXO does not increase so much, so in an environment like open sky, clock drift will maintain a relatively stable value. Meanwhile, in the case of an adverse condition where the buildings are lined up, short-term clock drift tends to be disturbed due to the GNSS caused by multipath signals and others. 28 GF-880X Protocol Specifications SE18-600-004-00 6.11 CRX (TPS2) – PPS Information Format: $PERDCRX , TPS2 , PPS output , PPS mode , PPS period , Pulse width , Cable delay , 1 2 Polarity , PPS type , 7 8 3 4 5 6 Estimated , Reserve1 , Reserve2 , Reserve3 , Reserve4 *hh accuracy 9 10 11 12 13 Field 1 Data TPS2 Range 0, 1 (1 byte) 2 PPS output 3 PPS mode 4 PPS period 5 Pulse width 6 Cable delay 7 Polarity 0, 1 (1 byte) 0 8 PPS type 1 (1 byte) 1 9 Estimated accuracy 0000 to 9999 (4 bytes) 9999 10 Reserve1 11 Reserve2 12 13 Reserve3 Reserve4 0 to 3 (1 byte) 0 (1 byte) 001 to 500 (3 bytes) -100000 to +100000 (7 bytes) -1.760 to +1.760 (6 bytes) 0000 (4 bytes) (8 bytes) (7 bytes) Default 1 1 0 Description Command name 0: 1PPS OFF 1: 1PPS ON Current PPS mode [*1] 0: Always stop 1: Always output 2: Output only when position and time fix 3: Output only when TRAIM is OK PPS output interval 0: 1PPS 500 PPS pulse width [msec] +000000 PPS cable delay [nsec] PPS polarity 0: Rising edge 1: Falling edge PPS type 1: VCLK PPS Displays the estimation accuracy of the GNSS time being calculated. For details of estimation accuracy, see the terms in Chapter 2. +0.000 Reserve field 0000 Reserve field - Reserve field Reserve field Example: $PERDCRX,TPS2,1,1,0,200,+000000,0,1,0005,-0.876,0000,00000000,+000000*0F PPS output: 1PPS ON PPS mode: Always output PPS period: 1PPS Pulse width: 200 msec Cable delay: 0 nsec Polarity: Rising edge PPS type: VCLK PPS Estimated accuracy: 5 nsec 29 GF-880X Protocol Specifications SE18-600-004-00 [*1] PPS mode When the PPS mode is 2, positioning is performed with more than 1 satellite in TO mode and 4 satellites or more in NAV mode. In SS mode and CSS mode, more than 4 satellites are necessary to calculate the estimated position, but even if it becomes 3 satellites or less, if it can receive more than 1 satellite, using the estimated position so far, processing equivalent to TO mode is performed with the few satellites, and PPS that is synchronized with the synchronization target is continuously output. When the PPS mode is set to 3, PPS is output only when satisfying all the conditions of PPS mode 2 and using the satellite that passed the TRAIM judgment. Reliability of PPS improves more than PPS mode 2. However, please note that holdover to 1PPS cannot be performed when the PPS mode is set to 2 or 3. 30 GF-880X Protocol Specifications SE18-600-004-00 6.12 CRY (TPS3) – Position Mode & TRAIM Format: $PERDCRY , TPS3 , Pos mode , Pos diff , Sigma threshold , Time , Time threshold , 1 2 3 4 5 6 TRAIM solution , TRAIM status , Removed SVs , Receiver status , Reserve *hh 7 8 9 10 Field 1 Data TPS3 Range - Default - 2 Pos mode 0 to 3 (1 byte) 1 3 Pos diff 0000 to 9999 (4 bytes) 1000 4 Sigma threshold 000 to 255 (3 bytes) 000 5 Time 000000 to 999999 (6 bytes) 000000 6 Time threshold 000000 to 604800 (6 bytes) 000000 7 TRAIM solution 0 to 2 (1 byte) 2 8 TRAIM status 0 to 2 (1 byte) 2 9 Removed SVs 10 11 Receiver status Reserve 00 to 03 (2 bytes) (10 bytes) (10 bytes) 00 0x00000000 0x00000000 11 Description Command name Positioning mode 0: NAV mode 1: SS mode 2: CSS mode 3: TO mode Difference between the fixed position (or the estimated position) and the calculated position calculated by the positioning calculation in this second. [meter] [*1] Sigma threshold which changes automatically to TO mode. [meter] When the threshold value is 0, it is not used. Current update times of estimated position This value increments by 1 during 3D positioning. Survey time threshold which changes automatically to TO mode. When the threshold value is 0, it is not used. TRAIM solution 0: OK 1: ALARM 2: Insufficient satellites being tracked TRAIM status 0: There are enough number of satellites in use 1: There are a number of satellites for alarm determination 2: Not enough satellites Number of satellites removed by TRAIM Receiver status [*2] Reserve field Example: $PERDCRY,TPS3,2,0003,001,002205,086400,0,0,00,0x00000001,0x00000000*0D Positioning mode: CSS mode Position difference: 3 [m] Sigma threshold: 1 [m] Update times: 2205 times Time threshold: 86400 times TRAIM solution: OK TRAIM status: There are enough number of satellites in use Removed satellites: 0 Receiver status: 0x00000001 (Antenna short) 31 GF-880X Protocol Specifications SE18-600-004-00 [*1] Reliability of fixed position When the position mode is SS, CSS, TO mode, the Pos Diff field displays the difference between the fixed position (or the estimated position created by integrating the position information for a certain period) and the position obtained by positioning calculation at that time in meters per second. This value can be used as an indicator of reliability of position information. For example, if this value continuously maintains a small value, it means that the fixed position is set correctly. Conversely, if this value continues to maintain a large value, there is a possibility that the fixed position being set is offset from the true value. If you know that the fixed position is set correctly, this value is an indicator of the reliability of the position information calculated every second. For example, if this value is stable and maintains a small value, the positioning calculation per second can be performed satisfactorily, and it can be inferred that the time calculated by positioning calculation and 1PPS is also good. Conversely, if this value becomes larger or smaller, it can be inferred that the reception environment is bad and the positioning calculation is disturbed under the influence of multipath. At this time, 1PPS stability is expected to deteriorate. Furthermore, this value can also be used for detection of anomaly of the antenna and spoofing signal. When this value suddenly jumped from a small value to a large value in spite of knowing that the fixed position was set correctly, it is expected to be caused by a sudden deterioration of the reception environment or a reception of a spoofing signal by a malicious person. In this case, since the time and 1PPS calculated from positioning calculation may be greatly jumped, risk avoidance is recommended in consideration of them. [*2] Receiver status The operation status of this product is displayed in BIT unit. The meaning of each BIT is as follows. If two or more BIT conditions are satisfied at the same time, they are displayed as a logical sum of these BITs. BIT (LSB=0) Item 00 to 03 Antenna current detection 04 to 07 Spoofing signal detection 08 to 11 Operation status of NLOSMASK mode 12 to 15 Energization time 16 to 19 20 to 23 24 to 27 Reserved Reserved Reserved 28 - 31 Antenna installation environment Description 0: Normal 1: Antenna short 2: Antenna open 3: No antenna voltage Notify when a spoofing signal is detected. [*3] 0: Spoofing signal is not detected. 1: Spoofing signal is being detected. Notify the processing status of multipath countermeasure set with the NLOSMASK command. 0: NLOSMASK mode OFF 1: Step 1 in NLOSMASK mode 2: Step 2 in NLOSMASK mode 3: Step 3 in NLOSMASK mode Total energization time since turning on the power supply of this product 0: Less than 1 hour 1: 1 hour elapsed 2: 1 day elapsed 3: 7 days elapsed 4: 30 days elapsed Determination result of the installation environment of the antenna connected to this product 0: No position fix or non-positioning environment 1: Open sky environment 2: Semi-shielding environment 3: High shielding environment 32 GF-880X Protocol Specifications SE18-600-004-00 [*3] When an apparent abnormality (excluding the unhealth satellite) is seen in the contents of the navigation message received from one of the GNSS satellites after the initial positioning using the appropriate GNSS satellite, while the message is being received, 1 is set for the bit of this field. Error messages found by this detection are discarded. Also, the satellite that broadcasts it will not be used for positioning. [*4] This field is used only for indicator, so this does not guarantee the timing performance. 33 GF-880X Protocol Specifications SE18-600-004-00 6.13 CRZ (TPS4) – VCLK Frequency and Control Format: $PERDCRZ , TPS4 , Freq mode , Phase skip flag , Alarm , Status , 1 2 3 4 PPS timing error 5 , 6 Freq error , Reserve1 , Learning time , Available time , Reserve2 *hh 7 8 9 10 Field 1 Data TPS4 Range - Default - 2 Freq mode 0 to 5 (1 byte) 0 3 Phase skip flag 0, 1 (1 byte) 1 4 Alarm 5 Status 00 to FF (2 bytes) 00 to FF (2 bytes) 11 Description Command name Frequency mode [*1] 0: Warm up 1: Pull-in 2: Coarse lock 3: Fine lock 4: Holdover 5: Out of holdover Phase skip flag [*2] 0: Automatic judge 1: Execute 00 Alarm [*3] 01 Status [*4] Time difference between the timing of the synchronization target and the PPS generated by the oscillator [nsec] 6 PPS timing error -999999999 to +999999999 (10 bytes) - 7 Freq error -99999 to +99999 (6 bytes) - 8 Reserve1 (4 bytes) - 9 Learning time 0000000 to 9999999 (7 bytes) 0 10 Available time 000000 to 999999 (6 bytes) 0 11 Reserve2 (7 bytes) - When the frequency mode is WARM UP, PULL IN, COARSE LOCK, FINE LOCK, the smaller this value, the more the 1PPS generated by the oscillator is synchronized with the synchronization target. VCLK frequency deviation [ppb] When the frequency mode is WARM UP, PULL IN, COARSE LOCK, FINE LOCK, the smaller this value, the closer the frequency output by the oscillator is to the nominal frequency. Reserve field Learning time for Holdover [sec] When this value exceeds the desired learning time, learning is satisfied. [*5] Holdover available time [sec] This value is set when learning is satisfied and decreases during holdover. [*5] Reserve field [*1] Frequency mode Figure 6.1 shows the state diagram of frequency mode. 34 GF-880X Protocol Specifications SE18-600-004-00 0. Warm up (A) 5. Out of holdover (F) 1. Pull-In (G) (H) (E) (B) (F) 4. Holdover 2. Coarse lock (G) (F) (D) (C) 3. Fine lock Figure 6.1 Frequency Mode State Diagram Transition (A) (B) (C) (D) (E) (F) (G) (H) Table 6.1 Transition Condition Use GNSS synchronization Use EPPS synchronization GNSS fix. EPPS input is confirmed. Warm up of the oscillator is completed. Warm up of the oscillator is completed. The oscillator is controlled to some extent, and The oscillator is controlled to some extent, and the timing is synchronized to some extent to the timing is synchronized to some extent to the synchronization target. (*1) the synchronization target. (*1) The oscillator is sufficiently controlled, and the The oscillator is sufficiently controlled, and the timing is synchronized with the timing is synchronized with the synchronization target. synchronization target. Timing accuracy deteriorated (e.g. jamming Timing accuracy deteriorated (e.g. jamming signal). Or, phase skip flg is 1. signal). Or, phase skip flg is 1. Timing stability is not stable, exceeding the Timing stability is not stable, exceeding the threshold for restarting control. (e.g. returning threshold for restarting control. (e.g. returning from Holdover) from Holdover) Or, phase skip flg is 1. Or, phase skip flg is 1. GNSS fix interrupts. (*2) EPPS input is no longer confirmed. (*2) GNSS fix again EPPS input is restarted. (More than 2 seconds GNSS fix is necessary (More than 2 seconds is necessary for for judgment) judgment) Holdover available time has become "0". Holdover available time has become "0". (*1) This transition condition can be changed by MODESET command. (*2) For Coarse lock or Fine lock, there is a mask period of up to 10 seconds. The mask period is intended to prevent frequent occurrence of temporary interference waves and GNSS reception interruption, and is set in anticipation of a period that does not fall outside the specification range. There is no specification regulation for holdover in case of EPPS input. 35 GF-880X Protocol Specifications SE18-600-004-00 [*2] Phase skip flag In order to shorten the control time in Pull in mode, this product can perform control called phase skip. Phase skip is to adjust the output PPS by changing the relationship of the pulse edge between VCLK frequency and VCLK PPS. Normally, while maintaining the relationship of the pulse edge between the VCLK frequency and VCLK PPS, the PPS is pulled into the synchronization target while gradually moving the VCLK frequency. Therefore, depending on the time difference from the synchronization target, it takes much time to control. On the other hand, using phase skip has the advantage that PPS can be controlled at high speed. However, there is a disadvantage that the pulse edge relationship temporarily collapses. Depending on the customer's equipment, it seems to be divided whether to shorten the synchronous control time or maintain the relation of the pulse edge. This product can set whether or not phase skip is performed by command. In this document, the flag which determines the phase skip is called phase skip flag. The settings related to phase skip can be set with the PHASESKIP command and the MODESET command. For details, refer to the section of each command. When the phase skip flag of the TPS4 sentence is 0, the phase skip is automatically determined based on the threshold set by the MODESET command. This is done only in Pull in mode. As a result, if the threshold value is exceeded, the phase skip flag temporarily changes to 1 and the phase skip is performed. After the phase skip, the phase skip flag returns to 0. When the phase skip flag of the TPS4 sentence is 1, the phase skip is always performed when the Pull in mode is reached. This setting is displayed mainly when setting to perform the phase skip forcibly with PHASESKIP command. After the phase skip, the phase skip flag returns to 0. The state transition diagram of the phase skip flag is as follows. 1 : Phase skip action (A) (B) 0 : Auto detect Transition (A) (B) Transition condition Phase skip has been completed. (The status transfer only when the frequency mode is "Pull-in".) PHASESKIP command is input. The threshold set by the MODSET command has been exceeded. (The status transfer only when the frequency mode is "Pull-In".) 36 GF-880X Protocol Specifications SE18-600-004-00 [*3] Alarm The alarm status of this product is displayed in BIT unit. The meaning of each BIT is as follows. If two or more BIT conditions are satisfied at the same time, they are displayed as a logical sum of these BITs. BIT (LSB=1) Item 01 to 02 Antenna current detection 03 Oscillator error 04 Oscillator control error 05 to 08 Reserved Description 0: Normal 1: Antenna current open 2: Antenna current short 3: Not displayed 0: Normal 1: Oscillator output error 0: Normal 1: Oscillator cannot be controlled (e.g. lifetime) [*4] Status The status of this product is displayed in BIT unit. The meaning of each BIT is as follows. If two or more BIT conditions are satisfied at the same time, they are displayed as a logical sum of these BITs. BIT (LSB=1) 1 Item Power supply to antenna pin 2 EPPS signal 3 Reference signal detection 4 5 6 7 8 Reserved Reserved Reserved For debugging Temperature correction data Description 0: OFF 1: ON 0: Not use EPPS and synchronizes with GNSS time 1: Synchronizes to the signal input to the EPPS pin Signal status of EPPS pin 0: Pulse is not detected 1: Pulse is being detected This BIT is set in the debug mode. This BIT is set when there is no temperature correction data. 37 GF-880X Protocol Specifications SE18-600-004-00 [*5] Learning time and Available time The counters in TPS4 sentence are set under the following conditions. frequency mode 0: Warm up 3: Fine lock 1: Pull-in 2: Coarse lock 4: Holdover 5: Out of holdover learning time “0” “++” (Upper limit: learning time set0 + 3600) available time “0” if leaning time ≧learning time set0: available time set0 else if ≧learning time set1: available time set1 else if ≧learning time set2: available time set2 else if < learning time set2: “--“ “0” “0” “--“ “0” The default values of learning time set0 to 2 and the available time set0 to 2 are below. These values can be set by HOSET command. Although you can change the conditions to shift to Holdover mode and the holdover period by setting the HOSET command, the holdover capability guaranteed by this product is only for the conditions described in the hardware specifications. Parameter learning time set0 available time set0 learning time set1 available time set1 learning time set2 available time set2 Default 259200 86400 3600 3600 0 0 At the timing when EPPS synchronization and GNSS synchronization are switched, the learning time is reset to 0. Examples of transition when all parameters are initial values are described on the next page. 38 GF-880X Protocol Specifications SE18-600-004-00 [Example 1] More than 3 days of learning is necessary for Holdover of 1 day. GNSS fixed GNSS Fine lock GNSS fixed Fine lock GNSS unfixed Holdover Out of holdover 259200 GNSS unfixed Out of holdover learning time available time 86400 learning time, available time mode < 259200 = 259200 time = 86400 [Example 2] Once it is in Holdover mode, more than 3 days of learning is necessary for Holdover of 1 day again. unfixed GNSS fixed mode Fine lock Fine lock 259200 GNSS fixed GNSS unfixed Holdover Out of holdover learning time Holdover available time 86400 learning time, available time GNSS = 259200 time = 259200 [Example] Even when GNSS is fixed again during Holdover, the Holdover available state will continue for one day after the first transition to Holdover. However, this does not apply if it is in Pull-in when re-positioning. unfixed GNSS GNSS fixed Holdover GNSS unfixed Fine lock Out of holdover 259200 Coarse or Fine lock learning time available time 86400 learning time, available time mode fixed = 259200 = 86400 39 time GF-880X Protocol Specifications SE18-600-004-00 6.14 CRG – QZSS L1S Disaster and Crisis Management Report Message The DC report message broadcasted with QZSS L1S signal is output. [*1] In order to receive messages in this sentence, it is necessary not only to output this sentence but also to be set to receive the QZSS L1S signal with the GNSS command. Format: $PERDCRG , DCR , 1 Field 1 2 Data DCR sequence 3 prn 4 type 5 dcreport sequence , 2 Range 1 to 4 Null, 83 to 91 Null, 43, 44, 63 XX・・・・・・・・X | | MSB LSB prn 3 , type , dcreport 4 *hh 5 Description QZSS L1S DC Report Sequence number of sentence PRN number of satellite broadcasted the message Message type [*2] Message is output when decoding is successful. It outputs 212 BITS (53 Bytes) which is the DATA FIELD part as a hexadecimal number sequence (0 to F). [*2] Example: $PERDCRG,DCR,1,85,43,7C4E43C001611580000000000000000000000000000000000004A*29 $PERDCRG,DCR,2,84,43,7C4E43C001611580000000000000000000000000000000000004A*2B $PERDCRG,DCR,3,,,*1F $PERDCRG,DCR,4,,,*18 [*1] This sentence outputs the information obtained by receiving the QZSS L1S signal as it is. The content of the DC report message needs to be interpreted by the host based on the user interface specification of the Cabinet Office. Please be aware that depending on the timing of message decoding, two different messages may be output from the same satellite in one second. Also, even if receiving a DC report message, when the CRC of the message does not match, Fields 3 to 5 of this sentence will be Null. [*2] When the prn is Null, this field is also Null. 40 GF-880X Protocol Specifications SE18-600-004-00 6.15 CRJ – Detection Status of Jamming Signal This sentence outputs the status of Anti-Jamming function. Format: $PERDCRJ , FREQ , 1 type , LineMax , Line 2 3 4 , Jamming 1 Freq , Jamming 1 Signal Peak , 5 Jamming 2 Freq 7 Field 1 Data FREQ Range - Default - 2 Type GP or GL - 3 4 LineMax Line 1 to 4 1 to 4 NULL NULL 5 Jamming 1 Freq NULL or 10 bytes NULL 6 Jamming 1 Signal Peak 1 ~ 255 NULL 7 Jamming 2 Freq NULL or 10 bytes NULL 8 Jamming 2 Signal Peak 1 ~ 255 NULL 6 , Jamming 2 Signal Peak *hh 8 Description Command name Frequency band of this sentence GP: GPS GL: GLONASS Total number of output lines for each band information Current output line for each band information First frequency of the jamming signal masked by the Anti-Jamming function is indicated by 4 digits of integer part and 5 digit of decimal part. Signal strength of the first frequency of the jamming signal masked by the Anti-Jamming function The larger the value, the stronger the jamming signal. Second frequency of the jamming signal masked by the Anti-Jamming function is indicated by 4 digits of integer part and 5 digit of decimal part. Signal strength of the second frequency of the jamming signal masked by the Anti-Jamming function The larger the value, the stronger the jamming signal. Example: $PERDCRJ,FREQ,GP,,,,,,*4F $PERDCRJ,FREQ,GL,1,1,1601.999787,171,,*4D Jamming signal in GPS band is not detected. In GLONASS band, frequency of 1601.999787 MHz is detected at signal strength 171 and masked by the Anti-Jamming function. [Precautions for use]  Anti-Jamming function works up to 8 channels only for GPS and GLONASS.  Up to 5 sentences may be output depending on the number of jamming signals being detected.  When detecting more than nine jamming signals, this function masks in order from the stronger signal. 41 GF-880X Protocol Specifications SE18-600-004-00 6.16 CRP – High Resolution Current Position This sentence displays position information with higher resolution than GNS or GGA sentence. Format: $PERDCRP , LatDegree , LonDegree 1 , 2 Field Data Range 1 LatDegree -90.0000000 to 90.0000000 2 LonDegree -180.0000000 to 180.0000000 3 Altitude -1000.00 to 18000.00 Altitude *hh 3 Description Current position (Latitude) [degree] [*1] A positive number means the north latitude and a negative number means the south latitude. Current position (Longitude) [degree] [*1] A positive number means the east longitude and a negative number means the west longitude. Current altitude [meter] [*1] Example: $PERDCRP,+34.1234567,-51.6543210,35.12*47 34.1234567 deg N 51.6543210 deg W Altitude: 35.12 m [*1] The fixed position is displayed in TO mode. 42 GF-880X Protocol Specifications SE18-600-004-00 6.17 CRQ – SAR / RLM Information Broadcasted by Galileo Satellites This sentence outputs the Search and Rescue (SAR) and the Return Link Message (RLM) received from Galileo satellites. Format: $PERDCRQ , SentNum , SentIndex , Prn_1 , Sar_1 [, Prn_2 , Sar_2 , 1 2 3 4 5 6 Prn_3 , Sar_3 , Prn_4 , Sar_4 ] 7 Field 1 2 Data SentNum SentIndex Range 1 to 2 1 to 2 3 Prn_1 01 to 36 or NULL 4 Sar_1 000000 to 3FFFFF or NULL 5 Prn_2 01 to 36 or NULL 6 Sar_2 000000 to 3FFFFF or NULL 7 Prn_3 01 to 36 or NULL 8 Sar_3 000000 to 3FFFFF or NULL 9 Prn_4 01 to 36 or NULL 10 Sar_4 000000 to 3FFFFF or NULL 8 9 *hh 10 Description Total number of CRQ sentence in this second Number for identifying the number of lines in this sentence Galileo satellite number that decoded the message (This field is NULL when it is impossible to decode the SAR/RLM) SAR/RLM message [*1] (This field is NULL when it is impossible to decode the SAR/RLM) Galileo satellite number that decoded the message (This field is NULL when it is impossible to decode the SAR/RLM) SAR/RLM message [*1] (This field is NULL when it is impossible to decode the SAR/RLM) Galileo satellite number that decoded the message (This field is NULL when it is impossible to decode the SAR/RLM) SAR/RLM message [*1] (This field is NULL when it is impossible to decode the SAR/RLM) Galileo satellite number that decoded the message (This field is NULL when it is impossible to decode the SAR/RLM) SAR/RLM message [*1] (This field is NULL when it is impossible to decode the SAR/RLM) Example: $PERDCRQ,2,1,01,2AAAAA,02,2AAAAA,10,100000,11,200000*41 $PERDCRQ,2,2,13,2AAAAA,35,2AAAAA,,,,*47 SAR/RLM are received from Galileo satellite 01, 02, 10, 11, 13, 35. $PERDCRQ,1,1,,*43 The receiver cannot decode the data or is not set to receive Galileo. [*1] It is data contained in I/Nav odd page that is decoded from Galileo E1-B signal. MSB is far leftmost bit. 43 GF-880X Protocol Specifications SE18-600-004-00 6.18 ACK – Output the Command Reception Check This sentence is output when this product receives the checksum of the command. Format: $PERDACK , Command , Sequence , Sub-command 1 2 *hh 3 Field 1 Data Command Range - Default - 2 Sequence -1 to 255 0 3 Sub-command - - Description First field of received command The number of times successful for the reception. It is added 1 whenever it succeeds in command reception, and 0 to 255 is repeated. When command reception is failed, -1 is returned. The positive number means ACK, and the negative number means NACK. Second field of received command Example: $PERDACK,PERDAPI,-1,PPS*72 PERDAPI,PPS command input is failed. 6.19 MSG – Event Driven Message This sentence is output when certain events occur. This is a sentence for FURUNO engineer use only. Format: $PERDMSG , key 1 Field 1 2 Data key string [, string ] *hh 2 Range - Default - Description Alphanumeric event indicator Description of event Example: $PERDMSG,1A*06 44 GF-880X Protocol Specifications SE18-600-004-00 6.20 VERSION – Software Version Format: $PERDSYS , VERSION , Device 1 Field 1 2 3 4 Data VERSION Device Version Reserve 5 DO type , Version , Reserve , DO type 2 Range GF-8801 GF-8802 GF-8803 GF-8804 GF-8805 3 Default - - 4 *hh 5 Description Command name Device name Version number Reserve field GNSSDO product type Example: $PERDSYS,VERSION,OPUS7_SFLASH_MP_64P,ENP708A1830501T,QUERY,GF8801*14 6.21 FIXSESSION – Fix Session This is a sentence for FURUNO engineer use only. It is automatically output at startup, restart, and initial positioning. Format: $PERDSYS , FIXSESSION , Reserve1 , Reserve2 , Reserve3 *hh 1 Field 1 2 3 4 Data FIXSESSION Reserve1 Reserve2 Reserve3 2 Range - 3 Default - 4 Description Command name Reserve field Reserve field Reserve field Example: $PERDSYS,FIXSESSION,OFF,37249,37.249*32 $PERDSYS,FIXSESSION,INIT*49 $PERDSYS,FIXSESSION,ON*52 45 GF-880X Protocol Specifications SE18-600-004-00 6.22 ANTSEL – Antenna Selecting This sentence is output when the following events occur: - Initialization at power on - Reception of $PERDSYS,ANTSEL,QUERY command - $PERDSYS,ANTSEL command input Format: $PERDSYS , ANTSEL , 1 Field 1 Data ANTSEL 2 Input 3 mode Input , mode 2 Range FORCE1L FORCE2 1LOW 2 *hh 3 Default - Description Command name FORCE2 GNSS antenna input setting FORCE1L,1LOW: Use #6(RF PIN) FORCE2,2: Use #RF(RF_COAX) 2 Example: $PERDSYS,ANTSEL,FORCE1L,1LOW*32 $PERDSYS,ANTSEL,FORCE2,2*2A 46 GF-880X Protocol Specifications SE18-600-004-00 7 Input Commands These are input commands for the protocol of the receiver. 7.1 API [GNSS] – Satellite System Configuration COLD restart (time also cleared) is run when satellite system configuration is changed from or to GLONASS only fix configuration. In the others configurations HOT restart is run. To turn off the use of GPS satellites, please also set the TIMEALIGN command properly. Format: $PERDAPI , GNSS , TalkerID , Gps , Glonass , Galileo , Qzss , Sbas/L1s *hh 1 Field 1 Data GNSS 2 TalkerID 3 2 3 4 Range AUTO LEGACYGP GN Default - Gps 0, 2 2 4 Glonass 0, 2 2 5 Galileo 0, 2 0 6 Qzss 0, 2 2 7 Sbas/L1s [*1] 0 to 4 1 GN Example: $PERDAPI,GNSS,AUTO,2,2,0,2,2*41 Use: GPS, GLONASS, QZSS(L1C/A), SBAS Not receive: QZSS(L1S) 5 7 6 Description Command name Talker ID See Section 5.3 for details. GPS setting 0: Do not receive 2: Receive GLONASS setting 0: Do not receive 2: Receive Galileo setting 0: Do not receive 2: Receive QZSS (L1C/A) setting 0: Do not receive 2: Receive SBAS / QZSS L1S 0: Do not receive either 1: Differential fix with SBAS 2: In addition to the above 1, SBAS is used in positioning calculation 3: Receive QZSS L1S (No SLAS correction) 4: Receive QZSS L1S (SLAS correction) Mask: Galileo [*1] SBAS and QZSS L1S cannot be received at the same time. Only one of them can be used. The current setting value can be checked by the following command. $PERDAPI,GNSS,QUERY*18 47 GF-880X Protocol Specifications SE18-600-004-00 7.2 API [PPS] – PPS Setting Various setting status of PPS can be confirmed by TPS2 sentence. Format: $PERDAPI , PPS , Type , Mode , Period , Pulse width , Cable delay , 1 2 3 4 5 6 Polarity *hh 7 Field 1 2 Data PPS Type Range VCLK Default VCLK 3 Mode 0 to 3 1 4 Period 0 0 5 Pulse width 500 6 Cable delay 1 to 500 -100000 to 100000 7 Polarity 0, 1 0 0 Description Command name VCLK stable PPS output mode [*1] 0: Always stop 1: Always output 2: Output when the time is fixed after GNSS position fix 3: In addition to the above 2, output when there is no TRAIM error PPS output interval 0: 1PPS (A pulse is output per second) PPS pulse width [msec] PPS cable delay [nsec] PPS is delayed by setting a positive value. PPS polarity 0: Rising edge 1: Falling edge Example: $PERDAPI,PPS,VCLK,1,0,200,0,0*05 PPS output mode: Always output PPS pulse width: 200 msec PPS cable delay: 0 nsec PPS polarity: Rising edge of PPS is synchronous with GPS, UTC (USNO) or UTC (SU) [*1] When using holdover, please use PPS mode 1. 48 GF-880X Protocol Specifications SE18-600-004-00 7.3 API [GCLK] – GCLK Frequency Setting Format: $PERDAPI , GCLK , 1 Mode 2 , Freq [, Duty 3 , Offset ] 4 Field 1 Data GCLK Range - Default - 2 Mode 0, 1 0 3 Freq 10 to 40000000 10000000 (10MHz) 4 Duty 50 50 5 Offset 0 0 *hh 5 Description Command name GCLK output mode 0: Do not output 1: Output GCLK frequency [Hz] Duty cycle 50 stable It is omissible after the 4th field. 0 stable Example: $PERDAPI,GCLK,1,10000000,50,00*41 GCLK output mode: Output GCLK output frequency: 10MHz The current setting value can be checked by the following command. $PERDAPI,GCLK,QUERY*12 [Notes on GCLK] GCLK frequency is a frequency output from GCLK pin of this product. Stability of GCLK PPS and GCLK frequency depends on the frequency value set with this command. For details, please refer to the hardware specifications. Also, there is jitter at the GCLK frequency. It is necessary to evaluate in advance whether it is appropriate for the application to be used. The clock edge of the GCLK frequency does not match VCLK PPS. (Non-coherent) 49 GF-880X Protocol Specifications SE18-600-004-00 7.4 API [SURVEY] – Position Mode Setting HOT restart is occurred when the position mode is shifted to the NAV mode. Format: $PERDAPI , SURVEY , Position mode [, Sigma threshold , Time threshold [, 1 2 3 4 Latitude , Longitude , Altitude ]] *hh 5 Field 1 Data SURVEY Range - Default - 2 Position mode 0 to 3 1 3 Sigma threshold 0 to 255 0 4 Time threshold 0 to 10080 0 5 Latitude -90.0000000 to 90.0000000 0 6 Longitude -180.0000000 to 180.0000000 0 7 Altitude -1000.00 to 18000.00 0 6 7 Description Command name Position mode [*1] 0: NAV mode 1: SS mode 2: CSS mode 3: TO mode Sigma threshold which changes automatically to TO mode. [m] When the threshold value is 0, it is not used. [*2] Time threshold which changes automatically to TO mode. [minute] When the threshold value is 0, it is not used. [*2] Latitude for hold position in TO mode. [degree] [*3] A positive number means the north latitude and a negative number means the south latitude. This field can be set only when position mode is 3. It accepts up to the seventh decimal place. Longitude for hold position in TO mode. [degree] [*3] A positive number means the east longitude and a negative number means the west longitude. This field can be set only when position mode is 3. It accepts up to the seventh decimal place. Altitude above sea level for hold position in TO mode. [m] [*3] This field can be set only when position mode is 3. It accepts up to two decimal place. Example: $PERDAPI,SURVEY,1,10,1440*74 Mode: SS mode When the variance value of the estimated position is 10 or less and the number of calculation times of the estimated position reaches 86400 times, it automatically transits to TO mode. $PERDAPI,SURVEY,3,0,0,37.7870,-122.4510,31*48 Mode: TO mode Sigma threshold: 0 Time threshold: 0 Fixed position: 37.7870 degrees north 122.4510 degrees west 50 Altitude: 31 m GF-880X Protocol Specifications SE18-600-004-00 B [*1] Whether the calculation result of the estimated position is discarded when changing the position mode is as follows. NAV F H G F H E SS I F TO A,C I H G,J I J G, CSS D Transition condition A B C D E F G H I J After first power on, or after factory restart (default) After power on in case that last mode is NAV mode. After power on in case that last mode is SS mode. After power on in case that last mode is CSS mode. After power on in case that last mode is TO mode. Set to NAV mode Set to TO mode (After initial positioning, or when fixed position input) Set to SS mode Set to CSS mode The condition of survey is satisfied. Note: This product starts in TO mode when the position mode changes to TO mode by satisfying the transition condition before power off. Survey position and number of times of survey process Discard Discard Discard Keep Keep Discard Keep Discard Discard Keep [*2] When both Sigma threshold and Time threshold are satisfied, the position mode transits to TO mode. If you want to use only one of the thresholds, set the threshold value of the one not used to 0. If both are set to 0, the mode will not change to TO mode. [*3] In some cases, the actual input position and the position indicated by the sentence may rarely differ slightly on the scale of the least significant digit. However, it is due to the conversion error of the coordinate system at sentence display, there is no problem in performance. Due to the convenience of trigonometric calculations, when the position near the North Pole and South Pole points is set, there may be some error included in the reflected position. 51 GF-880X Protocol Specifications SE18-600-004-00 [Note] Since the Time threshold and the Sigma threshold are set to 0 in this product in the default state, the mode does not transition to TO mode automatically. However, even in this state, by performing positioning for several hours in an open sky environment or for a few days in a semi-shielding environment, the calculation of the fixed position automatically converges and the state equivalent to the TO mode at a good fixed position . (Although it remains in SS mode, the position will eventually hardly move.) Even during the SS mode and the CSS mode, when there is more than one satellite, time (1PPS) is calculated appropriately using the fixed position calculated up to that time (processing equivalent to TO mode). Therefore, we recommend that you use the default settings unless your equipment needs to see the TO mode flag. The best performance can be obtained regardless of the reception environment. 52 GF-880X Protocol Specifications SE18-600-004-00 7.5 API [RESTART] – Restart Command The details of RESTART command are described below. This command does not delete the backup data in FLASH. Format: $PERDAPI , RESTART [ , Restart type ] 1 Field 1 2 *hh 2 Data RESTART Range - Default - Restart type HOT WARM COLD FACTORY - Description Command name Restart mode The backup data retained after restart varies depending on the restart mode. See Chapter 8 for details. When this field is omitted, the restart mode is HOT. Example: $PERDAPI,RESTART,COLD*08 Mode: COLD restart 53 GF-880X Protocol Specifications SE18-600-004-00 7.6 API [FLASHBACKUP] – Back up to FLASH ROM Format: $PERDAPI , FLASHBACKUP , Type 1 Field 1 Data FLASHBACKUP *hh 2 Range - Default - Description Command name Select the item to be stored in FLASH. Each bit corresponds to each command setting value. Please set by OR. When this command is entered more than once, only the command of the bit specified by this command is stored at the end. 2 Type 0x0000 to 0xFFFF 0x0000 0x00: Clear the data stored in FLASH 0x01: Back up GCLK command 0x02: Back up DEFLS command 0x04: Back up TIMEALIGN command 0x08: Reserved 0x10: Back up FIXMASK command 0x20: Back up GNSS command 0x40: Back up PPS command 0x80: Reserved 0x100: Back up NLOSMASK command 0x200: Back up SURVEY command [*1] 0x400: Back up HOSET command Reserved after 0x800 Example: $PERDAPI,FLASHBACKUP,0x03*4E Back up GCLK and DEFLS command setting. [*1] The SURVEY command cannot be backed up to FLASH in CSS mode and TO mode. Please use it in NAV mode or for threshold setting in SS mode. [Precautions for use]  The contents stored by this command are deleted by software update.  The contents stored by this command are not deleted by RESTART command (including FACTORY).  When this command is input, positioning is temporarily interrupted and HOT restart is performed thereafter.  Do not turn off the power for at least 4 seconds after this command input. The current setting value can be checked by the following command. $PERDAPI,FLASHBACKUP,QUERY*4F The response of QUERY is displayed in a command list format over multiple lines. An output example of backing up GCLK, DEFLS and TIMEALIGN is as follows. $PERDCFG,FORMAT,ESIP*4D $PERDAPI,GCLK,0,10000000,50,0*70 $PERDAPI,DEFLS,18*0A $PERDAPI,TIMEALIGN,4*37 $PERDACK,PERDAPI,5,FLASHBACKUP*56 54 GF-880X Protocol Specifications SE18-600-004-00 7.7 API [DEFLS] – Default Leap Second Setting Please send this command before initial positioning. COLD restart (time also cleared) is run when this command is input. Format: $PERDAPI , DEFLS , Sec 1 Field 1 2 Data DEFLS Sec *hh 2 Range -99 to 99 Default 18 Description Command name Default leap second Example: $PERDAPI,DEFLS,19*0B Default leap second: 19 second The current setting value can be checked by the following command. $PERDAPI,DEFLS,QUERY*49 55 GF-880X Protocol Specifications SE18-600-004-00 7.8 API [TIMEZONE] – Local Zone Time Setting The current setting value can be checked in ZDA sentence. (Except sec field) Format: $PERDAPI , TIMEZONE , 1 Sign , Hour , Minute 2 3 4 Field 1 Data TIMEZONE Range - Default - 2 Sign 0 to 1 0 3 Hour 0 to 23 0 4 Minute 0 to 59 0 5 Sec E, M E [, Sec] *hh Description Command name LZT sign 0: Positive 1: Negative This setting is applied only to the ZDA sentence. LZT (Hour) This setting is applied only to the ZDA sentence. LZT (Minute) This setting is applied only to the ZDA sentence. By using this field, user can change the relationship between 1PPS and time stamp of sentence. This setting is applied to all sentences which time is output. Please use this field by default as it is unnecessary. E: Time is output with the relationship of [* 1] below. Time stamp shows the time of next 1PPS output. This output mode is eSIP specification. M: Time is output with the relationship of [* 2] below. Time stamp shows the time of last 1PPS output. This output mode is M12 specification. Example: $PERDAPI,TIMEZONE,0,9,0*69 LZT: +9 hours 56 GF-880X Protocol Specifications SE18-600-004-00 [*1] Time = t Time = t + 1 Time = t + 2 Reference Time 1PPS Serial data Time = t + 1 Time = t + 2 25 - 75 ms 25 - 75 ms 25 - 75 ms [*2] Time = t Time = t + 1 Time = t + 2 Reference Time 1PPS Serial data Time = t Time = t + 1 25 - 75 ms 25 - 75 ms 57 25 - 75 ms GF-880X Protocol Specifications SE18-600-004-00 7.9 API [TIMEALIGN] – Time and PPS Alignment Setting Please send this command only before initial positioning of COLD start. Format: $PERDAPI , TIMEALIGN , Mode *hh 1 Field 1 2 Data TIMEALIGN Mode 2 Range 1 to 6 Default 2 Description Command name Select the output time and PPS synchronization target [*1] Example: $PERDAPI,TIMEALIGN,2*31 Apply the leap second to the output time, PPS synchronizes with UTC time. The output time means the time field of GNS, ZDA and TPS1 sentences. [*1] The details of each time alignment mode are as follows: Mode Output time PPS synchronization target 1 Leap second is ignored GPS time 2 UTC (USNO) time 3 UTC (SU) time 4 Leap second is applied UTC (EU) time 5 UTC (NICT) time 6 GPS time Description Ignore leap second and UTC parameter, output GPS time, and synchronize PPS with GPS time. Output time that leap second is applied. 1PPS is synchronized with UTC (USNO) time. [*] Reception of GPS satellite is required. Output time that leap second is applied. 1PPS is synchronized with UTC (SU) time. [*] Reception of GLONASS satellite is required. Output time that leap second is applied. 1PPS is synchronized with UTC (EU) time. [*] Reception of Galileo satellite is required. Output time that leap second is applied. 1PPS is synchronized with UTC (NICT) time. [*] Reception of QZSS satellite is required. Output time that leap second is applied. Ignore UTC parameter, and synchronize PPS with GPS time. The current setting value can be checked by the following command. $PERDAPI,TIMEALIGN,QUERY*49 [Restrictions] This command selects which satellite to acquire UTC parameters (leap seconds, leap second insertion timing, UTC correction coefficient, etc.). If not set properly, leap seconds update or leap second insertion may not be performed. Therefore, please set this command appropriately according to the setting with the GNSS command. In the default state, UTC parameters are acquired from the GPS satellites. When turning off the use of GPS satellites with the GNSS command, please select another satellite for UTC parameter acquisition again from the satellites set for use with the GNSS command. GLONASS broadcasts the time including the leap second and does not broadcast the cumulative value of the leap second. When Mode=1 is selected during GLONASS standalone positioning, in order to match the correct output time, it is necessary to set the correct default leap second with the DEFLS command beforehand. 58 GF-880X Protocol Specifications SE18-600-004-00 7.10 API [TIME] – Time Setting This command can be used before initial positioning only when all of the following conditions are satisfied. After October 11, 2037 that is the timing of internal rollover Not use GLONSS or Galileo Start up with no time backup By setting the appropriate current date with this command, it is possible to output the correct date even after internal rollover. For details of internal rollover, please also refer to the technical document (SE18-100-034). Format: $PERDAPI , TIME , Time of date , Day , Month , Year 1 Field 1 Data TIME 2 Time of date 3 4 5 Day Month Year 2 Range 00 to 23 00 to 59 00 to 59 1 to 31 1 to 12 2018 to 2099 3 4 Default 8 1999 *hh 5 Description Command name Set the current hour, minute, second with 2 digits each. It does not need to be accurate. Current day Current month Current year Example: $PERDAPI,TIME,021322,24,11,2020*64 Time: 02:13:22 on 24th November, 2020 [Restrictions]  This command is required to input correct date within +/- 512 weeks.  Do not use this command after position fix since the time obtained from satellites is used.  For the output time, please also refer to corresponding items in Chapter 2. 59 GF-880X Protocol Specifications SE18-600-004-00 7.11 API [FIXMASK] – Positioning and Satellite Mask Setting Format: $PERDAPI , FIXMASK , Mode , Elevmask , Reserve , SNRmask , 1 2 3 4 5 IDSM 6 Prohibit SVs Prohibit SVs Prohibit SVs Prohibit SVs Prohibit SVs , , , , (GPS) (GLONASS) (Galileo) (QZSS) (SBAS) 7 8 9 10 11 Field 1 2 Data FIXMASK Mode Range USER Default - 3 Elevmask 0 to 90 0 4 Reserve 0 0 5 SNRmask 0 to 99 0 6 IDSM Prohibit SVs (GPS) Prohibit SVs (GLONASS) Prohibit SVs (Galileo) Prohibit SVs (QZSS) 0 32BIT (HEX) 24BIT (HEX) 36BIT (HEX) 5BIT (HEX) 0 Prohibit SVs (SBAS) 19BIT (HEX) 7 8 9 10 11 0 0 0 0 0 [, ] *hh Description Command name Fixed value Elevation mask [degree] Only satellites at elevation above this value are used in positioning. Reserve field Signal level mask [dB-Hz] Only satellites with signal levels above this value are used in positioning. 0 stable GPS satellite number mask [*1] Lowest order bit means SV=01. GLONASS satellite number mask [*1] Lowest order bit means SV=65. Galileo satellite number mask [*1] Lowest order bit means SV=01. QZSS L1C/A Satellite number mask [*1] In order from the lowest BIT, 93, 94, 95, 96, 99 SBAS Satellite number mask [*1] Lowest order bit means SV=33. Set to 0 when using QZSS L1S signal. Example: $PERDAPI,FIXMASK,USER,10,0,37,0,0x00000092,0x000001,0x000000000,0x00,0x20000*60 Elevation mask: 10 degrees Signal level mask: 37 dB-Hz GPS mask: GPS (BIT2 = SVID 2), GPS (BIT5 = SVID 5) and GPS (BIT8 = SVID 8) GLONASS mask: GLONASS (BIT1 = SVID 65) SBAS mask: SBAS (BIT18 = SVID 50) [*1] Each BIT corresponds to one satellite. When entering, please add 0x to the beginning. Do not set the command with a length exceeding the range. The current setting value can be checked by the following command. $PERDAPI,FIXMASK,QUERY*52 60 GF-880X Protocol Specifications SE18-600-004-00 7.12 API [OCP] – Detailed Elevation and Azimuth Mask Setting The elevation mask can be set for each azimuth angle of 1 degree instead of the conventional unique elevation angle mask. It is useful when fixedly installing in an environment where there are many shields such as urban areas. When this command is used with the elevation mask of FIXMASK command, the higher mask value is applied. For example, if the elevation mask is set to 5 degrees with the FIXMASK command and the elevation mask of 30 degrees is set for the azimuth angle of 100 degrees with this command, the elevation mask 30 degrees is applied only at the azimuth angle of 100 degrees, and at the other azimuth angles the elevation mask 5 degrees is applied. Format: $PERDAPI , OCP , az_1 , el_1 [, az_2 , el_2 [, … [, az_9 , el_9 ] … ] *hh 1 Field 1 2 3 … 18 19 Data OCP az_1 el_1 … az_9 el_9 2 Range 000 to 359 00 to 99 … 000 to 359 00 to 99 3 4 Default 0 0 … 0 0 5 18 19 Description Command name Specify azimuth angle Set elevation angle for the azimuth angle specified above … Specify azimuth angle Set elevation angle for the azimuth angle specified above Example: $PERDAPI,OCP,015,45*1E Set elevation mask 45 degrees for azimuth angle 15 degrees. For all other azimuths, keep the state just before the command input. $PERDAPI,OCP,015,5,244,21*1B Set elevation mask 5 degrees for azimuth angle 15 degrees and elevation mask 244 degrees for azimuth angle 21 degrees. For all other azimuths, keep the state just before the command input. [Note] It is omissible after the 4th field. You can add 0 to the beginning or omit it. For example, if you input 015 or 15, it accepts the same as 15. 61 GF-880X Protocol Specifications SE18-600-004-00 The following command can specify an azimuth range and set an elevation mask for that range. It is convenient when you set the elevation mask manually. Format: $PERDAPI , OCP , RANGE , start_angle , end_angle , 1 2 3 Field 1 2 Data OCP RANGE Range RANGE Default - 3 start_angle 0 to 359 0 4 end_angle 0 to 359 0 5 elevation 0 to 90 0 4 elevation *hh 5 Description Command name Indicates that azimuth is specified as a range Start position of the azimuth angle range From this azimuth angle, specify the range in the clockwise direction. End position of the azimuth angle range Determines the azimuth range with this azimuth as the end point. Set this elevation mask for the range specified above Example: $PERDAPI,OCP,RANGE,15,45,60*77 Set the elevation mask 60 degrees in the range from 15 to 45 degrees in the clockwise direction. For all other azimuths, keep the state just before the command input. $PERDAPI,OCP,RANGE,330,15,45*41 Set the elevation mask 45 degrees in the range from 315 to 15 degrees in the clockwise direction. (That is, ranges from 315 to 359 degrees and from 0 to 15 degrees are specified.) For all other azimuths, keep the state just before the command input. [Note] The current set value can be checked by one of the following commands. Since this sentence has a lot of output, please choose according to the baud rate and the output of other sentences. $PERDAPI,OCP,QUERY*4D The setting value is output for all azimuth angles from 0 to 360 degrees. Since it is displayed in a total of 18 lines, the sentence output amount increases, and in some cases it may not be able to output all of them. $PERDAPI,OCP,QUERY1*7C The setting value is output for the first half azimuth angle from 0 to 180 degrees. It displays with a total of 9 lines. $PERDAPI,OCP,QUERY2*7F The setting value is output for the second half azimuth angle from 180 to 360 degrees. It displays with a total of 9 lines. 62 GF-880X Protocol Specifications SE18-600-004-00 The output format for QUERY is as follows. Format: $PERDAPI , OCP , num , el_0 , el_1 , … , el_19 *hh 1 2 3 4 Field 1 Data OCP Range - Default - 2 num 01 to 18 - 3 4 … 23 el_0 el_1 … el_19 00 to 99 00 to 99 … 00 to 99 0 0 … 0 23 Description Command name Current number of lines of OCP sentence. In case of 01, the elevation mask value for the azimuth angle 0 to 19 degrees is output, and in case of 02, the elevation mask value for the azimuth angle 20 to 39 degrees is output on that line. Elevation mask for azimuth angle “num * 20 + 0” degrees Elevation mask for azimuth angle “num * 20 + 1” degrees … Elevation mask for azimuth angle “num * 20 + 19” degrees Example: $PERDAPI,OCP,01,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*06 $PERDAPI,OCP,02,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*05 $PERDAPI,OCP,03,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*04 $PERDAPI,OCP,04,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*03 $PERDAPI,OCP,05,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*02 $PERDAPI,OCP,06,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*01 $PERDAPI,OCP,07,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*00 $PERDAPI,OCP,08,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*0F $PERDAPI,OCP,09,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*0E $PERDAPI,OCP,10,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*06 $PERDAPI,OCP,11,15,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00*03 $PERDAPI,OCP,12,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00*04 $PERDAPI,OCP,13,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00*05 $PERDAPI,OCP,14,00,00,00,00,00,00,00,00,00,00,45,45,45,45,45,45,45,45,45,45*02 $PERDAPI,OCP,15,45,45,45,45,45,45,45,45,45,45,45,45,45,45,45,45,45,45,45,45*03 $PERDAPI,OCP,16,45,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00*01 $PERDAPI,OCP,17,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00*01 $PERDAPI,OCP,18,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00*0E Elevation mask 15 degrees in the range from 0 to 200 degrees and Elevation mask 45 degrees in the range from 270 to 300 degrees are set. 63 GF-880X Protocol Specifications SE18-600-004-00 7.13 API [NLOSMASK] – NLOS Satellite Elimination Algorithm Setting We recommend using the default setting when there is no particular need. Format: $PERDAPI , NLOSMASK , mode 1 , Threshold1 , Threshold2 , Threshold3 2 3 Field 1 Data NLOSMASK Range - Default - 2 mode 0, 1 1 3 Threshold 1 0 to 3600 0 4 Threshold 2 0 to 99 30 4 *hh 5 Description Command name Algorithm to eliminate NLOS satellites [*1] 0：OFF / 1：ON Time to intentionally hold the positioning calculation after starting or restarting [second] [*2] Signal level mask which is limitedly set only until the probable position is calculated [dB-Hz] [*3] After calculating the probable current position, this mask setting will be invalid. Threshold for determining which satellite is the NLOS satellite [nsec] [*4] 5 Threshold 3 0 to 9999 50 The smaller the numerical value, the more severe the condition of LOS satellite. Example: $PERDAPI,NLOSMASK,1,1000,40,50*4C Use algorithm to eliminate NLOS satellites. Positioning is held for 1000 seconds after starting or restarting, and then positioning calculation will start. Signal level mask 40 [dB-Hz] is applied until the probable position is calculated, satellites below that are not used in positioning. After calculating the probable current position, the signal level mask 40 is canceled, and only satellites within the threshold value of 50 ns are used in time calculation. The current setting value can be checked by the following command. $PERDAPI,NLOSMASK,QUERY*1B [*1] Fine adjustment of this algorithm is possible by adjusting the threshold after the third field. 64 GF-880X Protocol Specifications SE18-600-004-00 [*2] Normally, general GNSS receivers tend to start positioning calculation as soon as possible when satellite signals can be received. This is because they are tuned for solutions that require the need to quickly fix the position for car navigation etc. On the other hand, in the timing solution focused on long-term time stability, it is important to continually determine the position and time rather than the initial positioning quickness. The setting tuned for car navigation is effective for getting rough location information quickly. However, depending on the positioning environment, there are concerns that positioning is performed with four satellites including only NLOS satellites and the initial position is determined. This is because even if LOS satellites can be found by searching enough time, positioning calculation is performed using the previously received satellites. In this case, position accuracy is bad and time accuracy may be affected. This field addresses such concerns. By setting a value in this field, deliberately delay the start of positioning calculation and set a period to focus only on satellite search. GNSS satellites generally broadcast almanac which is rough orbital information of the satellite in about 900 seconds cycle. By holding this time or more, it is possible to drastically reduce the loss of the satellite existing above the sky. The counter to be compared with this threshold value is unconditionally incremented every second regardless of the connection state of the antenna or reception environment after startup or restart. The counter is reset only at restart. This setting is not applied in the NAV mode. [*3] This field sets a signal level mask. The same setting can be done with the FIXMASK command. However, unlike the setting of the FIXMASK command which is executed at all times, this setting is applied only for a limited period until the probable position can be calculated. In general, the signal level mask is considered useful for eliminating NLOS satellites. The setting of an appropriate signal level mask is said to be useful for improving positioning accuracy. However, the persistent signal level mask has a problem that it is difficult to use because there is a possibility that the satellite interruption may be immediately caused when the reception environment deteriorates. This field focuses on determining the fixed position which has a particularly large effect on the calculation of time. The signal level is masked until the fixed position is roughly determined. After finding a certain position, the mask is released. As a result, positioning can be continued while ensuring time accuracy even in a badly conditioned environment with many shielding objects. When using the signal level mask of the FIXMASK command together, the higher mask value is applied. This setting is not applied in the NAV mode. [*4] This product is equipped with an algorithm that regards it as an NLOS satellite when the time until the satellite signal arrives at the receiver is later than the expected time. This field can fine-tune the threshold to determine it. Even satellites that do not satisfy the threshold set in this field are counted as positioning satellites and also displayed on the GSA sentence. Internally, the process of reducing the contribution to the positioning of the target satellite is applied. This setting may be applied even in the NAV mode. 65 GF-880X Protocol Specifications SE18-600-004-00 7.14 API [MODESET] – Frequency Mode Transition Condition Setting We recommend using the default setting when there is no particular need. Format: $PERDAPI , MODESET , Lock port , 1 2 Coarse lock threshold 3 Field 1 Data MODESET Range - Default - 2 Lock port 0 to 5 1 3 Coarse lock threshold 0 to 999999 GF-8801: 50000 GF-8802: 50000 GF-8803: 10000 GF-8804: 5000 GF-8805: 1500 4 Phase skip threshold 0 to 999999 0 , Phase skip threshold 4 *hh Description Command name Frequency mode for changing LOCK terminal to logic high (Lock) 0: Frequency mode is 2, 3 or 4 1: Frequency mode is 2 or 3 2: Frequency mode is 3 3: Frequency mode is 3 or 4 4: Always Logic L 5: Always Logic H PPS timing accuracy for changing the frequency mode from "Pull-in" to "Coarse lock" [nsec] GF-8801: