NMEA THS datagram format
The NMEA THS datagram provides the true vessel heading. The datagram includes a mode indicator field providing critical safety-related information about the heading data. The THS datagram replaces the deprecated HDT.
Format
$--HETHS,x.xx,a*hh<CR><LF>
Description
1 $—Talker identifier
2 HETHSDatagram identifier
3 x.xxHeading (Degrees)
4 aMode
•  AAutonomous
•  VThe data are not valid.
5 *hhChecksum