REFERENCE MANUAL - FTP Directory Listing - Trimble

NMEA 0183
C
General NMEA Parser Requirements
• When no position fix is available, some of the data fields in the NMEA
messages will be blank (i.e., no characters between commas), but selected
messages will output every second.
• Trimble varies the number of digits of precision in variable length fields, so
customer parsers should be able to handle variable lengths.
• NMEA parsers should be built to be forward-compatible. Future versions of a
standard message may have more fields or more choices per field.
• Checksum matching is strongly recommended.
• 9600 baud may be required if GSV messages are output.
• When multiple NMEA settings are implemented, save them to Flash memory.
• For GGA, GLL, RMC messages, time is GPS time (not UTC) until leap second
parameter is known. There is no way to tell which time your are running in,
until the time output suddenly decreases by 14 seconds (or by the current
offset).
• For GGA, GLL, RMC messages, if the datum is changed, there is no regular
DTM warning of non-WGS-84 datum as required by NMEA 2.1. You must
query the datum for this information.
Copernicus GPS Receiver 217