NMEA-GP-RMC

Description:

Standard NMEA: Recommended minimum specific GNSS data. This message contains time, date, position (in LLH coordinates), positioning mode, course over ground (COG), and speed (SOG) data provided by the GNSS receiver. RMC is the recommended minimum navigation data to be provided by the selected source.

This message is actually NMEA-GN-RMC, as it uses information from all GNSS constellations (GN), not GPS only (GP). However, we publish it as NMEA-GP-RMC to maximize compatibility.

Configuration:

• NMEA-GP-RMC_GNSS for combined (average) output from both receivers

  • The time and position data is the average between GNSS1 and GNSS2.

  • The fix type, number of satellites and PDOP values are from the “best” receiver.

  • The course over ground and speed over ground are computed from the average position and velocity between GNSS1 and GNSS2. Note that this is not the same as the average of the individual COG and SOG.

  • The message is only valid if both receivers have a valid fix.

• NMEA-GP-RMC_GNSS1 for output from GNSS 1 receiver

  • This is the standard NMEA RMC for GNSS1.

• NMEA-GP-RMC_GNSS2 for output from GNSS 2 receiver

  • This is the standard NMEA RMC for GNSS2.

• NMEA-GP-RMC_FUSION for output from Fusion

  • The time, position, course over ground and speed over ground data is from the Fusion solution.

  • The message is only valid if Fusion data is valid (Fusion initialized and propagation successful). Note that dead-reckoning mode is considered invalid, as specified by the NMEA specification.

  • The positioning mode is:

    • When fusion is using GNSS: The GNSS state (RTK fixed, RTK float, SPP) of the best GNSS receiver.

    • When fusion not using GNSS: Dead-reckoning or none depending on the state of fusion.

• NMEA-GP-RMC_GNSS1TOS for top-of-second 1Hz strict NMEA output from GNSS 1 receiver

  • Like NMEA-GP-RMC_GNSS1, but only the top-of-second message

  • Always strict NMEA (the high-precision NMEA configuration has no effect)

  • The intended use is for time sync applications that use the PPS output of GNSS1 (for example, gpsd and chrony)

  • See also NMEA-GP-GGA_GNSS1TOS

Notes:

• These messages does not contain any information that would let one tell them apart. Do not enable more than one of these in the same port.

• This message is according to NMEA 0183 v4.11 (and erratas).

• It uses the “GP” talker ID even though the navigation solution is multi-GNSS.

Example message:

$GPRMC,151227.40,A,4723.54036,N,00826.88672,E,0.0,81.6,111022,,,R*7C\r\n

Example message with non-standard high-precision fields:

$GPRMC,151227.3997,A,4723.5403567,N,00826.8867153,E,0.00000,81.6172,111022,,,R*4F\r\n

Message fields: