NMEA-GP-HDT

Description:

Standard NMEA: True heading. This message contains the actual vessel heading (from the Fusion solution) in degrees. “True” means the geometric North (not the magnetic North). Note that this is not the heading of motion (direction of travel) but the orientation of the sensor.

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

We recommend using the FP_A-ODOMETRY.orientation_* and FP_A-ODOMETRY.vel_* fields to calculate the heading of motion. See Appendix C to understand how to extract the heading from the FP_A-ODOMETRY message.

Example message:

CODE

$GPHDT,61.7,T*05\r\n

Example message with non-standard high-precision fields:

CODE

$GPHDT,61.7183,T*3F\r\n

Message fields:

#	Field	Format	Unit	Nullable	Example	Description
1	`heading`	Float (.1/.4)	deg	Y	`61.7`	True heading
2	`true_ind`	Character	-	Y	`T`	Always `T`

Notes:

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.