The GRS message is used to support the Receiver Autonomous Integrity Monitoring (RAIM).
Note – Because the contents of this NMEA message do not change significantly during a one-second interval, the receiver outputs this message at a maximum rate of 1 Hz.
An example of the GRS message string is:
|0||Message ID $GPGRS|
|1||UTC of GGA position fix|
0: Residuals used to calculate position given in the matching GGA line
1: Residuals recomputed after the GGA position was computed
|3–14||Range residuals for satellites used in the navigation solution, in meters|