Garmin GPS 25 LP Technical Specification

Garmin GPS 25 LP Technical Specification Manual pdf 39 page image

35Appendix DPhase Output Data Binary FormatTwo records are transmitted once per second by the GPS 25LP. One record contains primarily post-process information such as position and velocity information. The second record contains receivermeasurement information. The records are sent at a default baud rate of 9600 baud, 8 bits, no parity.Records begin with a delimiter byte (10 hex). The second byte identifies the record type (28 hex for aposition record, 29 hex for a position record). The third byte indicates the size of the data. The fourthbyte is the first byte of data. The data is then followed by a chksum byte, a delimiter byte (10 hex), andan end-of-transmission character (03 hex).Note - If RTCM-104 differential data is sent to the GPS 25LP the board will reset the Phase Output Databaud rate to the same baud rate used for RTCM-104 data. If the differential inputs are used on the GPS25LP then the RTCM-104 data must be sent to the GPS 25LP at 9600 baud (preferred) or 4800 baud.RTCM-104, baud rates less than 4800 baud are not supported by the GPS 25LP since it would limit busbandwidth past the point where a once per second phase output data rate could be maintained.Position Record- 0x10 (dle is first byte)- 0x28 (position record identifier)- 0x36 (size of data)- cpo_pvt_type (see description below)- one byte chksum (the addition of bytes between the delimiters should equal 0)- 0x10 (dle)- 0x03 (etx is last byte)typedef struct{float alt;float epe;float eph;float epv;int fix;double gps_tow;double lat;double lon;float lon_vel;float lat_vel;float alt_vel;} cpo_pvt_type;alt ellipsoid altitude (mt)epe est pos error (mt)eph pos err, horizontal (mt)epv pos err, vertical (mt)fix 0 = no fix; 1 = no fix; 2 = 2D; 3 = 3D; 4 = 2D differential; 5 = 3D differential;6 and greater - not definedgps_tow gps time of week (sec)lat Latitude (rad)