Author Topic: GPS auto SRTM altitude  (Read 3834 times)

Offline szebenyib

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GPS auto SRTM altitude
« on: February 26, 2014, 21:44:18 »
Hi!

Would it be possible to use SRTM data in altitudes? I know one can fill it after a track has been created. However I have not found a way yet to do that real-time while hiking/cycling and the data normally recorded is not precise, as my phones capabilities are not outstanding in this aspect, no matter what I set in the altitude manager.
So is it technically possible to have an additional option next to optimize GPS altitude to instead of optimizing it would allow to:
a - optimize (nothing changes to existing functionality)
b - real-time SRTM data update while en route (would consume mobile data)
c - real-time SRTM data update while en route if offline downloaded hgt files are present (for example from openmaps.eu)

If that is not a viable option, can track recording have an option to auto fill the altitude once the recording has been saved?

 

Offline Menion

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Re: GPS auto SRTM altitude
« Reply #1 on: February 27, 2014, 07:56:07 »
Hi,

are you sure that GPS altitude is much worst then computed altitude?

Anyway there are two options in alttiude manager ( http://support.locusmap.eu/hc/en-us/articles/200028131-Altitude-manager ) that may helps here.

Section "Elevation data" and "Altitude filter". So enable "Elevation data" and set stronger altitude filter. This should help a lot
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Offline szebenyib

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Re: GPS auto SRTM altitude
« Reply #2 on: February 27, 2014, 13:19:20 »
Unfortunately yes, it's not +/-10m but rather +/-100m, see the screenshots attached. The trend is visible but SRTM is precise. I could not find a better graph however I can remember that I have started replacing altitude data because it was even worse then in these charts. And if there is precise data I don't want to use anything else instead if possible. This way I always have to manually "fill altitude" after having ended a trip.
 

Offline szebenyib

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Re: GPS auto SRTM altitude
« Reply #3 on: February 28, 2014, 11:32:07 »
Went for a run today and the deviation is really big, see screenshots.
Before, after, and another scrot from mytourbook.
 

Offline voldapet

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Re: GPS auto SRTM altitude
« Reply #4 on: March 03, 2014, 08:47:32 »
Hi,

I'd suggest to download Geoid model and use automatic correction:
Open Altitude Manager
Enable Altitude offset
tab offset check "Automatic correction"
Confirm changes using "SET" button and confirm downloading Geoid file (if missing)

Would you test if are GPS altitudes better (with automatic offset settings), please?
 

Offline szebenyib

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Re: GPS auto SRTM altitude
« Reply #5 on: March 03, 2014, 10:52:45 »
Hi,
I'll check it of course :-) maybe I will have time for it at the weekend.
 

Offline szebenyib

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Re: GPS auto SRTM altitude
« Reply #6 on: March 07, 2014, 19:22:33 »
It's not helping unfortunately. Altitude values are rather inaccurate. Geoid stuff was downloaded and active.
They are more than 200% of what they should be.
 

Offline tommi

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Re: GPS auto SRTM altitude
« Reply #7 on: March 08, 2014, 06:23:30 »
It's not helping unfortunately. Altitude values are rather inaccurate. Geoid stuff was downloaded and active.
They are more than 200% of what they should be.
Are the screenshots from a jogging track? If yes, I guess the maxspeed 20.1km/h is crazy compared to average 9.9km/h or are you doing extreme interval training?
 

Offline szebenyib

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Re: GPS auto SRTM altitude
« Reply #8 on: March 08, 2014, 09:35:56 »
It is from a jogging track, however it had some really steep parts. Somewhere as steep as 10% gradient, so for short periods my speed was that high (strictly downwards :D). I have checked other tracks including those parts and they had equal speed there.
 

Offline Menion

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Re: GPS auto SRTM altitude
« Reply #9 on: March 09, 2014, 10:31:24 »
hmm very interesting.

Two questions
1) what device you use?
2) if you, directly in Locus, "fill altitude" for such recorded track, results are OK?
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Offline szebenyib

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Re: GPS auto SRTM altitude
« Reply #10 on: March 09, 2014, 14:22:03 »
I use a Sony xperia P. It is not the best in terms of GPS (no glonass), but it is still acceptable for me till I buy a new one maybe in one and a half years.
If I fill the altitude manually it is perfect. Checking it with mytourbook I can see that the altitude after filling is exactly the SRTM altitude which is the best for me.