Altitude corrcetion methode

Skully Fox shared this question 2 months ago
Answered

Hi,

About Settings-Altitude manager-Automatic correction

Manual says,

"Locus Map can compute offset of the whole world from a Geoid model."

I wonder what geoid model algorithm Locus app uses for calculating geoid height?

(e.g. EGM2008, EGM96, EGM84 ...)

And can you show me the source code of it?


Secondly,

When I check 'Altitude NMEA correction' altitude is differ from my raw NMEA data.

for example GPGGA sentence (MSL height 100M, and Geoid height 20M)

How locus calculate Altitude using those data?

Comments (1)

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Hello Skully,

currently we use 15-minute based EGM96 model (it is stored in Locus/data/srtm/WW15MGH.DAC file). In case of automatic correction, values are interpolated from this file with basic linear interpolation.

In case of NMEA correction, Locus pick the height of geoid above WGS84 ellipsoid (position 11 in GPGGA). Final point altitude is then measured altitude + NMEA offset.

If you think, any value is computed incorrectly, give me please coordinates (in case of automatic correction) or part of the recorded NMEA file (for NMEA correction).

Menion

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Thank you for quick reply, Menion.

It was satisfactory explanation. Automatic correction was fully precise for me.

Have a good day.

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