Question about NULL in position_data4

10 months 1 week ago #2434 by liu1322

I have a question about NULL values seen in position_data4. It seems like sometimes there is a "rawmsg" but the corresponding "lat" "lon" and "alt" are filled in as NULL.
Ex): rawmsgmintimemaxtimemsgcounticao24nicsupplahcrnicsurvstatusnicsupplboddbaroaltlatlonaltnicsupplcgroundspeedgsresolutionheadingtimeflagsurfacehourserialmintime.1maxtime.10 8facb89c5937664328c9a104fcd0 40:18.740:18.71 acb89c  false     185.290 false      true   true     NULL  NULL  NULL  false      NULL         NULL          NULL     false     false   1.67E+09-1.4E+0940:18.740:18.7
I'm wondering what causes the result to be NULL? I tried globally unambiguous CPR decoding using the given "rawmsg", it seems like the "rawmsg" can be decoded and can pass the CRC check. I'm curious about what are the common cases corresponding to have a NULL in "lat" "lon" and "alt".


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