Author Topic: Question on altitude optimization  (Read 414 times)

Offline neatwheat

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Question on altitude optimization
« on: May 07, 2020, 10:05:49 »
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!
 

Offline menion

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Re: Question on altitude optimization
« Reply #1 on: May 07, 2020, 12:45:28 »
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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Offline neatwheat

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Re: Question on altitude optimization
« Reply #2 on: May 11, 2020, 19:37:52 »
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?
 

Offline menion

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Re: Question on altitude optimization
« Reply #3 on: May 12, 2020, 09:47:11 »
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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Offline neatwheat

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Re: Question on altitude optimization
« Reply #4 on: May 12, 2020, 12:25:36 »
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.




 

Offline poutnikl

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Re: Question on altitude optimization
« Reply #5 on: May 12, 2020, 12:32:17 »
(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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When a user digs profiles up from the GitHub repositories,
they will be hopefully wrapped in some wiki knowledge....  :-)
Try also https://github.com/poutnikl/Brouter-profiles/wiki/Determining-optimal-bicycle-profile
 
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Offline neatwheat

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Re: Question on altitude optimization
« Reply #6 on: May 13, 2020, 16:24:03 »
(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
 

Offline Saturo

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Re: Question on altitude optimization
« Reply #7 on: May 13, 2020, 19:13:40 »
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."
 

Offline menion

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Re: Question on altitude optimization
« Reply #8 on: May 14, 2020, 07:59:23 »
Little offtopic .. anyway no, possible small difference between "what you see on the dashboard" vs "audio coach" is not yet solved.
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Offline neatwheat

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Re: Question on altitude optimization
« Reply #9 on: May 15, 2020, 16:30:58 »
@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?)