Locus destroys barometric altitude data with srtm values

joeloc shared this problem 1 year ago
Not a Problem

Locus tries to "optimize" barometric altitude data with srtm values. This is wrong. Barometric altitudes are as good as they get, no srtm fiddling can improve that, even with hires data. The steeper your terrain, the worse srtm will be.


Locus altitude manager settings specifically says "optimize GPS altitude values with srtm" and that does indeed make sense. But please do not apply this "optimization" to barometric data, it will only make it worse. Imho barometric values also shouldnt be run through Locus altitude filter.

Comments (2)

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2

Well the above claims about barometric altitude superiority are very conditional. They have superior short range space and time stability, what is no doubts great for calculation of total ascend/descend. But its long range space and time stability is inferior.

While GPS or SRTM based altitude measurement can gain a lot from barometric short term stabilty , for long term it is vice verse.

If pressure changes fast near fronts or the pressure lows, or if there is significant vertical motion in extreme ( wrt 15- 0.0065.h ) temperatures, barometric altitude gets significant bias.

Optimal altitude filter would get advantage of all GPS, SRTM and barometer. E.g. by getting altitude primarily from barometer, but this altitude would be in long term corrected by filtered barometer vs GPS bias.

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Hello guys,

not sure what to do with this "problem". In some previous month was a discussion and change in system of altitude manager. I have received mostly positive feedback so I consider now as final solution. If there will be anyway some recorded non senses, please let me know.

Because it is quite sensitive topic, I may in this case imagine creating some special option that will print out into file all parameters that Locus use for this feature (time, pressure, srtm elevation etc.), for some "excel" test and post process. But only if there will be any problems ...