RT_INS_Dir_Dist_To_Start_Mark: INS Direct Time and Distance to Start Marker
RT_INS_Dir_Dist_To_Start_Mark: 142, 28 (0x8D2220 + unit id) (0x3A2)
Bytes 0-3: Direct time to start marker (s)
Bytes 4-7: Direct distance to start marker (m)
Time to marker resolution is s/1000.
Distance to marker resolution is m/1000.
Validity and impact flags are provided by RT_INS_Lat_Dist_To_Start_Mark.