Jackson Labs RSR GNSS Transcoder, Руководство пользователя

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RSR GNSS Transcoder™ User Manual
70 © 2017 Jackson Labs Technologies, Inc.
4.10.3 GPS:SATellite:TRAcking:COUNt?
This query returns the number of satellites being tracked.
4.10.4 GPS:SATellite:VISible:COUNt?
This query returns the number of satellites (PRN) that the almanac predicts should be visible, given
date, time, and position.
4.10.5 NMEA Support
The following commands allow the RSR GNSS Transcoder™ to be used as an industry standard
navigation multi-GNSS receiver. The GPGGA, GPGSV, GPRMC, PASHR and GPZDA NMEA
commands comprise all necessary information about the antenna position, height, velocity, direction,
satellite info, fix quality info, time, date and other information that can be used by standard
navigation applications via the USB serial interface.
Once enabled, the unit will send out NMEA sentences on the USB port automatically every N
seconds. All incoming serial commands are still recognized by the unit since the serial interface
transmit and receive lines operate completely independently of one another.
For compatibility with existing GPS-only products, the units’s NMEA output only uses the GPS
NMEA sentence headers (GPGGA, GPGSV, etc.) regardless of the GNSS systems enabled on an
external uBlox receiver. Also, the GPGSV output uses a modified satellite numbering scheme as
detailed in Section
4.10.9 to allow multiple, and possibly concurrent GNSS system satellites to be
differentiated in the GPGSV message.
Please note that due to internal double-buffering that the position, direction, and speed data is
delayed by one second from when the external GNSS receiver reported these to the internal
Microprocessor, so the position is valid for the 1PPS pulse previous to the last 1PPS pulse at the time
the data is sent (one second delay). The time and date are properly output with correct UTC
synchronization to the 1PPS pulse immediately prior to the NMEA data being sent.
Once set, the following command settings will be stored in NV memory, and generate NMEA output
information even after power to the unit has been power cycled.
By default NMEA strings are not generated until at least one external 1PPS reference pulse has been
received. The unit can be set to output NMEA data asynchronously and regardless of the external
1PPS pulse status by using the ON setting of the SYNC:OUT:1PPS:RESET command as described
in Section
4.7.11
4.10.6 GPS:GPGGA
This command instructs the RSR GNSS Transcoder™ to send the NMEA standard string $GPGGA
every N seconds, with N in the interval [0,255]. The command is disabled during the initial warm-up
phase.
This command has the following format:
GPS:GPGGA <int> [0,255]
GPGGA shows height in MSL Meters.