User's Manual

A NMEA-0183 Output
164 Trimble R7/R8 GPS Receiver User Guide
TrimbleR7/R8 GPS Receiver Operation
This appendix describes the formats of the subset of NMEA-0183
messages that are available for output by the receivers. For a copy of the
NMEA-0183 Standard, go to the National Marine Electronics
Association website at www.nmea.org.
A.1 NMEA-0183 Outputs
When NMEA-0183 output is enabled, a subset of NMEA-0183 messages
can be output to external instruments and equipment connected to the
Trimble R7/R8 receivers serial ports. These NMEA-0183 messages let
external devices use selected data collected or computed by the GPS
receiver.
All messages conform to the NMEA-0183 version 3.01 format. All begin
with $ and end with a carriage return and a line feed. Data fields follow
comma (,) delimiters and are variable in length. Null fields still follow
comma (,) delimiters but contain no information.
An asterisk (
*) delimiter and checksum value follow the last field of data
contained in an NMEA-0183 message. The checksum is the 8-bit
exclusive OR of all characters in the message, including the commas
between fields, but not including the $ and asterisk delimiters. The
hexadecimal result is converted to two ASCII characters (0–9, A–F).
The most significant character appears first.
Table A.1 summarizes the set of NMEA messages supported by the
Trimble R7/R8 receivers, and shows the page where detailed
information about each message can be found.
Table A.1 NMEA message summary
Message Function Page
AVR Time, yaw, tilt, range, mode, PDOP, and
number of SVs for Moving Baseline RTK
167
GGA Time, position, and fix related data 168
GSA GNSS DOP and active satellites 169
GST Position error statistics 170