AtomicGPS speed of movement - unit of measurement?

  • Hello,

    I'm trying to get speed of movement of GPS module (AtomicGPS) using your example product code via GPS.s_GNRMC.TrackSpeed parameter from GPSAnalyse::AnaGPRMC function in GPSAnalyse.cpp.

    It seems this parameter returns speed values but in unknown (for me) scale.

    I've compare with speed measurement with my car measurement (kmh) and it seems AtomicGPS, results about half of the real speed (but there is correlation I think).

    What is unit of measurement returned by this function in example library??


  • Any hints?

  • @macle

    Hi. I don’t have the AtomicGPS, but I did some digging around to try to understand the speed measurement within the GPSAnalyse.cpp file. I see this in that file relating to speed: _s_GNRMC.TrackSpeed = _s_GNRMC.pamstr[7].toFloat();

    Doing a quick google search on “GNRMC speed” I found this source that says GNRMC ground speed is in knots. Doing the conversion between knots and kph (1 knot =
    1.852 kilometers per hour), it seems about right that the GPS is reporting a speed measurement that is roughly half of your vehicle speed in kph (0.54 to be exact!).

    Hope this helps!