RT_INS_Pos_LLH_1: Accuracy and INS Latitude
RT_INS_Pos_LLH_1: 142, 2 (0x8E0220 + unit id) (0x382)
Byte 0: Validity
Byte 1: Accuracy latitude
Byte 2: Accuracy longitude
Byte 3: Accuracy altitude
Bytes 4-7: INS Latitude (degrees)
Latitude resolution is degrees * 1e-7.
The validity byte is used for the data packets in this message *and* in RT_INS_Pos_LLH_2.