Wed Feb 26 16:16:35 EET 2003 MPRS packet format MPT 1327 signalling standard for trunked LMR systems packet: bitsync 16 or more alternating bits, ending with "0" wordsync SYNC Word 11000100 11010111 0x4? "MPRS" 0x40=normal, 0x41...0x4F inclusive are reserved. 5 bytes packed callsign (6 characters) and ssid (4 bits) 1 byte reserved for routing/digipeating "going up/downstream at level X" 3 bytes latitude 7F 3F 7F 0x80 of 1st byte: "destination" (GPRMB) or "position" (GPRMC) 3 bytes longitude FF 3F 7F 2 bytes CRC (AX25 way, MSB first, bytes between wordsync and crc, seed FFFF, complemented) callsign and ssid: ascii chr - ' ' gives 6 bits per chr, from ' ' (SPACE) to '_' inclusive. 3/4 reduction. ssid is just binary 0...15. 00000000 11111111 22222222 33333333 44444444 55555555 ssid unpacked 11000000 22221111 33333322 55444444 ssid5555 packed L L L L L L L S S S S S S S b b b b b b b latitude: 7F degrees 0...90 0x80: set if coords are "destination" instead of current position. 3F minutes 0...59 0xC0: 2 MSbits of station symbol 7F decimal minutes 0...99 0x80: South hemisphere flag. longitude: FF degrees 0...180 3F minutes 0...59 0xC0: 2 LSbits of station symbol 7F decimal minutes 0...99 0x80: West hemisphere flag. station symbol: Selected from APRS primary table. Translation from 4-bit number into APRS symbol happens at the MPRS-APRS gateway. 0 'p' rover 1 '>' car 2 'v' van 3 's' ship 4 '-' house 5 '+' red cross 6 'r' antenna 7 'c' orienteering marker 8 '0' [0] 9 '1' [1] A '2' [2] B '3' [3] C '4' [4] D '5' [5] E '6' [6] F '7' [7]