drives/gps: add new sensor_gnsss_relative msg

- for ublox this corresponds to NAV_RELPOSNED

msg/CMakeLists.txt

@@ -144,6 +144,7 @@ set(msg_files
 	sensor_combined.msg
 	sensor_correction.msg
 	sensor_gps.msg
+	sensor_gnss_relative.msg
 	sensor_gyro.msg
 	sensor_gyro_fft.msg
 	sensor_gyro_fifo.msg

msg/sensor_gnss_relative.msg

@@ -0,0 +1,30 @@
+# GNSS relative positioning information in NED frame. The NED frame is defined as the local topological system at the reference station.
+
+uint64 timestamp                  # time since system start (microseconds)
+uint64 timestamp_sample           # time since system start (microseconds)
+
+uint32 device_id                  # unique device ID for the sensor that does not change between power cycles
+
+uint64 time_utc_usec              # Timestamp (microseconds, UTC), this is the timestamp which comes from the gps module. It might be unavailable right after cold start, indicated by a value of 0
+
+uint16 reference_station_id       # Reference Station ID
+
+float32[3] position               # GPS NED relative position vector (m)
+float32[3] position_accuracy      # Accuracy of relative position (m)
+
+float32 heading                   # Heading of the relative position vector (radians)
+float32 heading_accuracy          # Accuracy of heading of the relative position vector (radians)
+
+float32 position_length
+float32 accuracy_length
+
+bool gnss_fix_ok                  # GNSS valid fix (i.e within DOP & accuracy masks)
+bool differential_solution        # differential corrections were applied
+bool relative_position_valid
+bool carrier_solution_floating    # carrier phase range solution with floating ambiguities
+bool carrier_solution_fixed       # carrier phase range solution with fixed ambiguities
+bool moving_base_mode             # if the receiver is operating in moving base mode
+bool reference_position_miss      # extrapolated reference position was used to compute moving base solution this epoch
+bool reference_observations_miss  # extrapolated reference observations were used to compute moving base solution this epoch
+bool heading_valid
+bool relative_position_normalized # the components of the relative position vector (including the high-precision parts) are normalized