GPS-Sport ForenRun.GPS SoftwareError: Where do topographic altitude data come from?
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r0bis 19.06.2013 14:44:10 UTC



Well, this is good to know, thank you for the reply. What confused me was that I read somewhere in forums that the GPS altitude was generally error prone and I thought that topographic altitude might be used then and it would influence the results if all of a sudden I climbed 100 metres up. That is an interesting problem - how much the altitude data influence calorie count, because for terrain like along the Thames it should not influence much, however if one runs in German Alps, that would influence the result a lot, wouldn't it?

Curiously enough in this particular case - the place in photo as can be seen has been used for transit of sand and other building related bulk material, so when the SRT Mission was taking place, it is conceivable that there was a high pile of sand (but unlikely 100 m) very near to the path.
admin786557 17.06.2013 12:52:14 UTC



The data comes from the SRTM space shuttle mission: http://en.wikipedia.org/wiki/Shuttle_Radar_Topography_Mission. The original data has been error-corrected and smoothened, but obviously, some errors remain in it.

It does not influence calorie count because if you start an actual training, gps based altitude data will be used to compute the ascent used for calorie calculation.

I'm afraid correcting this is almost impossible because of the huge amount of global altitude data.
r0bis 17.06.2013 09:54:31 UTC geändert am 17.06.2013 10:12:08 UTC

Big ascent of 100 m where terrain is actually flat

I have created a route for which I noticed a very steep ascend and descent on topographic altitude. In actual fact there is no such thing on the ground on the bank of the Thames.

There are a few problems with this:
-- Theoretically this should influence calorie count and similar factors
-- This gives wrong data to the training log

I experimented with rearranging the route around the place. It is as if there was an invisible hill. If I make a detour through the river the ascent/descent peak disappears.

How can this anomaly be corrected?

Route: http://www.gps-sport.net/routes/O2-%285%29_129302
[1]Red blotch shows approx location of the invisible hill
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