Raytheon STD 21 GPS Operation Manual page 104

• NMEA 0183 Format THS
$- - - -THS,x.x,a*hh<CR><LF>
3717/110--850.DOC020002
HRP ⇒ True Heading and Status
Checksum
Mode indicator (see note)
Heading, degrees true
Sentence identifier
THS = True Heanding and Status
NOTE Mode indicator: This field should not be null.
A = Autonomous
E = Estimated (dead reckoning)
M = Manual input
S = Simulator mode
V = Data not Valid (including standby)
Satellite Compass
STD 21 GPS
96
Edition: Jan. 16, 2009