... the user friendly GPS tool


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Elevation Adjustment
#1
Hi:

I have a track that the GPS has recorded an incorrect elevation, it's about 100m difference to another track that I recorded a month or so later (how odd is that??).

Anyway... I know that RC can get the elevation from geoNames.org (and it works well -- reduced the elevation to something I'd expect), but my concern is that if I did that for the whole track then I'd "lose" what the GPS has recorded. Does that make sense, or is that assumption incorrect??

So, what I was wondering is if it'd be a better alternative to have a "tool" to adjust the track's elevation by +/- n metres? Say my first point is 117m too high I could adjust all the track's points by -117m (thereby keeping the on-the-ground relativity of the recordings).
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#2
(03.01.2011, 10:03)scribbly Wrote: Anyway... I know that RC can get the elevation from geoNames.org (and it works well -- reduced the elevation to something I'd expect),

Since 2.0 RouteConverter uses a 3 level lookup for the elevation data:

  1. download and usage of SRTM3 data
  2. web service lookup to geonames.org
  3. web service lookup to earthtools.org

(03.01.2011, 10:03)scribbly Wrote: but my concern is that if I did that for the whole track then I'd "lose" what the GPS has recorded. Does that make sense, or is that assumption incorrect??

You could only select the positions which you want to change? And there is always undo/redo :-)

(03.01.2011, 10:03)scribbly Wrote: So, what I was wondering is if it'd be a better alternative to have a "tool" to adjust the track's elevation by +/- n metres? Say my first point is 117m too high I could adjust all the track's points by -117m (thereby keeping the on-the-ground relativity of the recordings).

This doesn't seem to be a common use case. But if you implement it and send me a patch, I'll have a look at it.
--
Christian
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#3
(03.01.2011, 10:11)routeconverter Wrote:
(03.01.2011, 10:03)scribbly Wrote: but my concern is that if I did that for the whole track then I'd "lose" what the GPS has recorded. Does that make sense, or is that assumption incorrect??

You could only select the positions which you want to change? And there is always undo/redo :-)

Sorry, not clear enough... I want to adjust all the positions, not just some.

I guess this is not too common, but I thought it was odd that the GPS was out and stayed out? But it did, as the track was a circuit and got back to the same elevation Sad
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#4
(03.01.2011, 10:20)scribbly Wrote: Sorry, not clear enough... I want to adjust all the positions, not just some.

So you want to add/subtract an offset from all positions?
--
Christian
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#5
I see this is an old thread, but nice to see that someone else have the same ideas as me.

I have a track started at see level, but my GPS has recorded all points 92 meter too low. It starts at -88 meter. The track has 8.3k points so a edit on this is not that important. Not my python skills either.. yet.

Did you find a solution to your problem scribbly?
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#6
(26.09.2013, 12:09)Ciryaher Wrote: I see this is an old thread, but nice to see that someone else have the same ideas as me.

I have a track started at see level, but my GPS has recorded all points 92 meter too low. It starts at -88 meter. The track has 8.3k points so a edit on this is not that important. Not my python skills either.. yet.

Did you find a solution to your problem scribbly?

No... I'm still holding my breath that this 'simple' fix may be implemented at some stage.
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#7
(26.09.2013, 12:25)scribbly Wrote: No... I'm still holding my breath that this 'simple' fix may be implemented at some stage.

Well, you could check out the source code, hack a menu item below Extras, a dialog for the offset to add/subtract and modify the elevations of all positions by the offset. If you like, send me a patch and I'll try to integrate it.
--
Christian
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#8
So far you will never get accurate altitude information from gps as altitude signal is artificially imprecise for private usage. You need a device with a barometric pressure sensor to get reliable altitude information. The deviations of gps changes also periodically, therefor a simple offset correction will not be necessarily successful.

Grüße,
Ilmari
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