Garmin GPS 20x Technical Specifications page 18

Satellite Data Record
The satellite data has a record ID of 0x72 with 84 (0x54) data bytes. The data bytes contain data for 12 satellites as
described below.
typedef struct
{
uint8 svid; //space vehicle identification (1–32 and 33–64 for WAAS)
uint16 snr;
uint8 elev; //satellite elevation in degrees
uint16 azmth;
uint8 status;
} cpo_sat_data;
The status bit field represents a set of booleans described below:
Bit
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 12 satellites for a total of 12 X 7 bytes = 84 (0x54) bytes.
The USB Packet for the Satellite Record looks like:
- 0x14 0x00 0x00 0x00 (USB Transport ID, 1 byte unsigned, 4 bytes reserved)
- 0x72 0x00 0x00 0x00 (Record ID, 2 bytes unsigned, 4 bytes reserved)
- 0x54 0x00 0x00 0x00 (Number of data bytes, 4 bytes unsigned)
- 12 cpo_sat_data records
190-00880-00
//signal-to-noise ratio
//satellite azimuth in degrees
//status bit-field
Meaning when bit is one (1)
GPS 20x Technical Specifications
Page 15
Rev. A