nmea 0183 output from gps help

Discussion in 'OnBoard Electronics & Controls' started by bigbear69, Jan 22, 2010.

  1. bigbear69
    Joined: Aug 2008
    Posts: 32
    Likes: 0, Points: 6, Legacy Rep: 10
    Location: New Zealand

    bigbear69 Junior Member

    just a question regarding nmea output strings from my gps unit.
    I have a jrc gps/sounder combo and I have connected a multi data repeater to it. this displays speed/ depth and temp. have sorted out the speed and temp all works fine but the temp doesn't display properly. my output string from the gps for temp is '$INMTW,+20.8,C*35

    the repeater reads something completely different. I was just wondering if most temp output strings on other units have a '+' or '-' before the numerical temp value.
    the manufacturer of the repeater says this + is wrong and the repeater can't read it properly. Is this true or shall I return the repeater and but another brand.

    Or is there anyway I can change the data string output so there is no '+' in the string.
    any help much appreciated.
  2. Tim B
    Joined: Jan 2003
    Posts: 1,438
    Likes: 59, Points: 0, Legacy Rep: 841
    Location: Southern England

    Tim B Senior Member

    This website http://www.maperl.com/Hydrography/ shows other $INMTW sentences without the '+'. It is possible that the GPS manufacturer's interpretation of the standard varied from other people's. However, no NMEA parser should struggle with a +/-, so it does seem that the manufacturer of the repeater is being rather unhelpful.

    Alternatively, you can use openPilot to read your NMEA stream, then with a few additions to the code you can make it output a new NMEA string without the '+'. You can also use it to display your position (when I've finished re-writing the plotting!), provide track/heading, satellite details, time, speed, temperature, and pretty much anything else you can think of.


    Tim B.
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