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"Top of Europe", wrong elevations

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Hello,

We visited 3 caches at the 'Top of Europe' in Switzerland. The elevations listed are too low. We read the FAQ considering elevation calculation and understand the problems regarding elevations. Still, there are differences between the srtm3 heights shown in geonames and the heights listed in Project GC.

GC39FJD http://api.geonames.org/srtm3?lat=46.54745&lng=7.98512&username=demo, result is 3466, listed in project GC is 3407
GC2QE08 http://api.geonames.org/srtm3?lat=46.54625&lng=7.98243&username=demo, result is 3396, listed in project GC is 3357
GC3MQT3 http://api.geonames.org/srtm3?lat=46.54753&lng=7.98165&username=demo, result is 3441, listed in project GC is 3414

The differences are not very large, but we still wonder what causes the differences. Are the SRTM3 data updated so often?
asked Jul 30, 2017 in Bug reports by Lingezicht (120 points)

1 Answer

0 votes

I believe the answer is given in FAQ - How is the elevation data calculated? 

"So what we do is that we interpolate between the 4 closests values to get a weighted average for the geocache location. In an area which is very hilly, like mountains, this will give a quite big fail factor and almost always a too low value."

The API calls you gave are presumably giving a single elevation value. Project-GC uses the four closest with a weighted average. The FAQ states that in mountainous regions this usually gives lower values than the actual elevation.

answered Aug 1, 2017 by sumbloke (Expert) (30,470 points)
The OP states that they've read the FAQ (I made the same mistake of not reading the question!)
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