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Compressed Position Determination - Source Code

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  • Lynn W. Deffenbaugh (Mr)
    To the keepers of the OpenTracker source code - Please read below... ... If you update the APRS parser source code as shown below in every detection for the
    Message 1 of 1 , Jun 26, 2009
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      To the keepers of the OpenTracker source code - Please read below...

      Lynn W. Deffenbaugh (Mr) wrote:
      > Symbol The presence of the leading Symbol Table Identifier instead of a
      > digit indicates that this is a compressed Position Report and not a normal lat/long report.
      >
      > Ok, so the Symbol Table Identifier NOT being a digit is what makes this
      > a compressed position report. But an overlay of 5 replacing the / or \
      > means that a digit appers after the ! which means this is NOT a
      > compressed position report. Catch-22. You might try an alpha overlay
      > rather than a digit, that might work. You might also want to note the
      > following when working with overlays:
      >
      > PS. The OpenTracker APRS packet parser explicitly checks for \ or / to
      > identify a compressed position report. Using a digit is definitely
      > against the spec, but some parsers (possibly all) won't like compressed
      > packets with anything but \ or /.
      >
      If you update the APRS parser source code as shown below in every
      detection for the compressed format (there are 4 of them in my copy), an
      alpha-based overlay in a compressed packet is correctly parsed.
      Numerics as an overlay character are invalid according to the spec:

      // Position
      //if (packet_data[1] == '/' || packet_data[1] == '\\')
      if (!isdigit(packet_data[1]))
      { // Compressed format

      Lynn (D) - KJ4ERJ - Benefactor of Open Source!
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