Garmin LVC 18 Technical Specification - Page 31

Satellite Data Record The satellite data has a record ID of 0x72 with 84 (0x54) data bytes. The data bytes contain the data for the 12 channels as described below. For each satellite, the following data is available: typedef struct { uint8 svid; //space vehicle identification (1-32 and 33-64 for WAAS) uint16 snr; //signal-to-noise ratio uint8 elev; //satellite elevation in degrees uint16 azmth; //satellite azimuth in degrees uint8 status; //status bit-field } cpo_sat_data; The status bit field represents a set of booleans described below: Bit Meaning when bit is one (1) 0 The unit has ephemeris data for the specified satellite. 1 The unit has a differential correction for the specified satellite. 2 The unit is using this satellite in the solution. This pattern is repeated for all 12 channels for a total of 12 X 7 bytes = 84 (0x54) bytes : typedef struct { cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data } cpo_all_sat_data The RS-232 Packet for the Satellite Record looks like: - 0x10 (DLE is first byte) - 0x72 (Record ID - single byte) - 0x54 (Number of data bytes - single byte) - cpo_all_sat_data - 0x## (2's complement of the arithmetic sum of the bytes between the delimiters) - 0x10 (DLE) - 0x03 (ETX is last byte) GPS 18 Technical Specifications (190-00307-00) Page 25 Rev. D