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gweis.1
Visitor II
July 12, 2022
Question

Can I read a negative altitude with Teseo-LIV3 GNSS Module ?

  • July 12, 2022
  • 1 reply
  • 850 views

Hi everyone,

I need to read system altitude with Teseo-LIV3 GNSS Module and I would like to know if I can read a nagative altitude with it ?

The only place I can see altitude is at page 97 of the User Manual in (--GGA frame) but it is described as "Height above mean sea level, max: 100000m", does this means that it can not send negative altitudes ?

Thanks in advance,

Regards,

Gaspar Weisbuch.

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    1 reply

    T
    Tesla DeLorean
    Graduate II
    July 12, 2022

    I'd expect it to report what it measures. Where it has applied a MSL (EGM96) type correction, in GGA, I'd expect you'd be able to back that out mathematically. http://lefebure.com/articles/nmea-gga/

    The resolution of the EGM96 grid is probably poor, if you have a finer grained local geoid surface, you could use that instead, or establish a local sea/ground level wrt WGS84, and apply that offset.

    If you're in an open cast pit, below sea-level, but with a sky view, I'd anticipate a negative values from a signed computation. The operational ceiling for commercial/consumer GPS/GNSS is of the order of 50-80km, and speeds below Mach 1.5.The reasons for these should be reasonably obvious, and I'm not sure anyone quotes lower, or negative limits, as the signals won't penetrate the underground or through water well.

    Alternatively if it can report position in an ECEF form you can apply whatever ellipsoid, geoid, datum translations you want on the host side.

    I'd give you more Teseo specific response, but I play for team u-Blox..

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