Improving Elevation gain/loss of recorded tracks

[panda]

Hello,

when I startet with om and made my first track recordings, I wondered why the measurement of Elevation gain/loss via gps is far away from reality.

Sometimes it's double of the real value (measured with bike computer barometer, which gives good results on stable weather conditions, my phone has no barometer).

I also tried to use DEM-data or online-elevation service to correct the data afterwards, but with few success. Sometimes it's even worse than gps data.



Of course I know, the main issue is, that gps based measurement of height is not very accurate and it varys up to some meters all the time.

So therefore it is necesary to make some averaging to get better height values.

I don't know how om does this, perhaps orux can contribute this, but I think it can be improved.



Here are the details of my test:

I made a trip with bike with one steep uphill, then some km flat, and then steep downhill, distance 18 km.

The correct Elevation gain/loss should be about 800m.

Oruxmaps tells me: 1150m, this is more than 40% off.



Then I took all the gps data (750 points) into Excel and added all Elevation gain/loss from point to point: this gives 1570m - even worse than OM.

(the data shows many small ups and downs, which is wrong)

Averaging #1 (5 points):  I made an average of height every 5 points and added the Elevation gain: 946 m

Averaging #2 (10 points): I made an average of height every 10 points and added the Elevation gain: 886 m



So with averaging 10 points it's only 10% off the value which is pretty good for gps based measures.



Of course this is only an example, perhaps tracks with other profile will lead to other results, but I guess that better averaging the elevation data

will lead to better Elevation gain/loss data.

[mntr86]

Hi,  i suggest you to use altitude from dem file and tap on "interpolate dem file".  With this Method i solved my problem of uncorrect altitude.

[Maxpil]

Hello,

when I startet with om and made my first track recordings, I wondered why the measurement of Elevation gain/loss via gps is far away from reality.

Sometimes it's double of the real value (measured with bike computer barometer, which gives good results on stable weather conditions, my phone has no barometer).

I also tried to use DEM-data or online-elevation service to correct the data afterwards, but with few success. Sometimes it's even worse than gps data.



Of course I know, the main issue is, that gps based measurement of height is not very accurate and it varys up to some meters all the time.

So therefore it is necesary to make some averaging to get better height values.

I don't know how om does this, perhaps orux can contribute this, but I think it can be improved.



Here are the details of my test:

I made a trip with bike with one steep uphill, then some km flat, and then steep downhill, distance 18 km.

The correct Elevation gain/loss should be about 800m.

Oruxmaps tells me: 1150m, this is more than 40% off.



Then I took all the gps data (750 points) into Excel and added all Elevation gain/loss from point to point: this gives 1570m - even worse than OM.

(the data shows many small ups and downs, which is wrong)

Averaging #1 (5 points):  I made an average of height every 5 points and added the Elevation gain: 946 m

Averaging #2 (10 points): I made an average of height every 10 points and added the Elevation gain: 886 m



So with averaging 10 points it's only 10% off the value which is pretty good for gps based measures.



Of course this is only an example, perhaps tracks with other profile will lead to other results, but I guess that better averaging the elevation data

will lead to better Elevation gain/loss data.

Have you tried the last Beta version (5.5.23 Beta 30)? It seems to go better.

[panda]

Hi,  i suggest you to use altitude from dem file and tap on "interpolate dem file".  With this Method i solved my problem of uncorrect altitude.

Hello,

finally at the weekend I made some tests with the setting you recommend and with the latest beta (36).

Now the ele gain is between 5% and 20% higher than my barometer device.

Especially on a ripled surface with many small ups and downs it's approx 20% too high.

I think this range is not perfect, but it's acceptable.



So the setting "use altitude from dem file and tap on "interpolate dem file"" is the best for oruxmaps to calculate the ele gain.

Of course the values depends on the resolution of the DEM files, at the moment I use the free 3" - files.

In another post I read, that the 1" DEM files will soon be freely available, so there's hope for even better ele gain values :-)

[mntr86]

Hi,  usually I use the standard 30 my dem file in oruxmaps.  The medium error is always under 10 %.  I think that depends from the region.  I test it in nw of italy.