NMEA-0183 message: HDT
Heading from True North
The heading computation in this message is computed from the moving baseline vector, which requires a two-antenna system.
An example of the HDT string is:
$GPHDT,123.456,T*00
                                                            
Heading from true north message fields
| 
                                                                             Field  | 
                                                                        
                                                                             Meaning  | 
                                                                    
|---|---|
| 
                                                                             0  | 
                                                                        
                                                                             Message ID $GPHDT  | 
                                                                    
| 
                                                                             1  | 
                                                                        
                                                                             Heading in degrees  | 
                                                                    
| 
                                                                             2  | 
                                                                        
                                                                             T: Indicates heading relative to True North  | 
                                                                    
| 
                                                                             3  | 
                                                                        
                                                                             The checksum data, always begins with *  |