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guides:apx

APX

APX is an experimental binary packet format for transmitting location information from a payload.

Packet Format

Offset Name Size Description
0 Packet Type 1 0x76 - Position
1 Callsign 6 Callsign of the user / payload. The format is described below
7 Timestamp 5 UTC timestamp
12 Latitude 4 Latitude (-90 - 90 degrees, 0.000000042 degree accuracy, or ~0.46cm accuracy)
16 Longitude 4 Longitude (-180 - 180 degrees, 0.000000084 degree accuracy, or ~0.93cm accuracy at the equator)
20 Altitude 3 Altitude (-8388608 - 8388607 cm, or -83.8 - 83.8 km, two's compliment)
23 Fix Status 1 0 = No Fix, 1 = Fix, >= 2 undefined
24 PDOP 1 Positional dilution of precision
25 Heading 1 Heading (0 - 360 degrees, 1.4 degree accuracy)
26 Ground Speed 1 Ground speed (0-100 m/s, 0.39 m/s accuracy)
27 Vertical Speed 1 Vertical speed (0-100 m/s, 0.39 m/s accuracy)
28 Checksum 4 32-bit CRC
32 FEC 32 Reed-Solomon forward error correction data. This may be omitted for storage, or if the mode already provides FEC

Sizes and offsets are in bytes, with each packet being 64 bytes in total (or 32 bytes with no FEC data).

guides/apx.txt ยท Last modified: 2011/11/19 00:38 by fsphil