Question on altitude optimization

Started by neatwheat, May 07, 2020, 10:05:49

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neatwheat

Hi! I would like to ask some information on altitude tracking before I go ahead and buy the pro version -

1.I am particularly interested how the  option to "optimize gps altitude" via smrt will work? Is it smoothing the curve in post or calibrating the gps from time to time etc?

2. Can I import LIDAR data and will the above optimization then use this data instead?

thanks in advance!
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Menion

Hello,

basic information may be found here: https://docs.locusmap.eu/doku.php?id=manual:user_guide:tools:altitude#srtm_data . LIDAR data in HGT format (SRTM-1, SRTM-3) are supported and you may use custom data by placing files into Locus/data/srtm directory.
Hope this helps.
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neatwheat

Thanks for your reply, I got me the Pro Version meanwhile and did some testing. It seems like that altitude optimization via smrt is done after saving the track, and optimized values are only visible inside Locus, so if I export the gpx it contains the standard gps altitude data, is that correct?
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Menion

Everything you set in "Altitude manager" is applied immediately after the GPS location is received. After that, an updated location (in this case with updated altitude value) is sent to other services like track recording. So all recorded points already contain this updated altitude. Original altitude is lost.

Why you have feeling that SRTM data are not exported? If you use the "Replace" option in "SRTM data" settings (Altitude manager), you should get quite a fluent elevation profile, exactly the same as with the "Fill elevation" option (in track detail).
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neatwheat

Thanks for explaining! I only noticed it when using "optimize gps altitude", because the lowest and highest points had different values when viewing the gpx outside Locus. When using the "replace" option it is indeed quite fluent and seems to stay pretty much identical outside of Locus.
(Note: To view gpx tracks I do not use services that calculate gpx altitude data from their own terrain model, so this should not be a source of error)

But since I intend to mostly use the "replace" option it isnt really a problem for me anyway, so thanks for the help.




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poutnikl

Quote from: neatwheat on May 12, 2020, 12:25:36
(Note: To view gpx tracks I do not use services that calculate gpx altitude data from their own terrain model, so this should not be a source of error)

It is also possible if the altitudes are (partially) GPS based ( even if optimized ), the online service internally filters noisy data. If altitudes are SRTM based, there is nothing to filter, as it is smooth.



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neatwheat

Quote from: poutnikl on May 12, 2020, 12:32:17
Quote from: neatwheat on May 12, 2020, 12:25:36
(Note: To view gpx tracks I do not use services that calculate gpx altitude data from their own terrain model, so this should not be a source of error)

It is also possible if the altitudes are (partially) GPS based ( even if optimized ), the online service internally filters noisy data. If altitudes are SRTM based, there is nothing to filter, as it is smooth.

Sent from my Xiaomi MI A2 / Android 10, via Tapatalk


Hmm I now viewed it via two other well known osm Apps too and it's the same - I don't think they use a filter by default
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Saturo

Is this issue yet solved?

"I have noticed that the value announced in the Audio Trainer for the vertical meters uphill is different from the value shown in the dashboard.
The value in the Audio Trainer is always lower."
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Menion

Little offtopic .. anyway no, possible small difference between "what you see on the dashboard" vs "audio coach" is not yet solved.
- Official help (ideas, questions, problems): help.locusmap.eu
- Advanced topics, sharing of knowledges: you're here!
- LM 4 Beta download, LM 4 Release download
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neatwheat

@menion 
One more question if you don't mind - does the "fill elevation" option completely replace altitude data of a track with smrt data? (So it would be basically be the same result as if you choose "replace gps values" before recording?)

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