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+1 vote

There is an Earthcache that is at sea level - you have to be on a ferry boat to do the earthcache. I found the following in the FAQ:

I found a cache with a faulty elevation

Sadly there are a lot of geocaches with these issues. The elevation data does not come from since it doesn't have that data. We have therefore built our own SRTM-service for the purpose, it currently serves SRTM v3.0. As a fallback for the areas this doesn't cover, we use to OpenElevation (OpenStreetMap) and the Google Elevation API.

If you find that a value in Project-GC isn't correct. Please read below how our elevation data works, and also check other services like for example Geonames. If you find out that other services has about the same fault tolerance, then there is nothing to do.

We do not do manual changes in the data. But if you find an entry that seems to be off by a lot more than in other services, feel free to report it so that we can investigate.

The Earthcache in question is Fraser River Plume. I have checked on Geonames, and as the location is in the ocean, it returns -32768. Per their documentation for the SRTM3 API request:
ocean areas have been masked as "no data" and have been assigned a value of -32768
I think Project GC should use a value of ZERO for all locations that return -32768 as the elevation from the geonames API.
Everyone who has logged this Earthcache has been awarded (in error) the "Diamond Low Altitude Cacher" badge on the BadgeGen page in Profile Stats.
in Bug reports by brilang (250 points)

1 Answer

0 votes
The depth of the ocean is ~250 meters in this spot, that's what's used. Since the coordinates aren't three dimensional Project-GC can not know if it's surface level or not. In case of the ocean it can be on the surface, or at the bottom. In case of land, it can be on the surface, in a high building, or deep below in a mine.

This is not an uncommon issue, every mystery cache in the ocean brings the same problem.
by magma1447 (Admin) (234k points)
Not a good answer. I have a cache GC1D49B published in a 6m deep lake at about sea level that is giving me -944m and a diamond badge!
Why isn't the answer good? Everything in it is true, and it has nothing to do with GC1D49B.

GC1D49B is located 3100 meters above sea level btw.
Oops, sorry. Wrong cache. It is GC397JN that is less than 20m from sea level that is at -944m
GC397JN is listed at Lake Wairaranapa, NZ.
It shows -944 m, but the lake itself is at around +11 m (Geonames lists it correctly, also to the trads at the shore), and the lake a a maximum depth of 2.5 meters

So -944m seems indeed a bit off... actually it would make it 5th deepest lake in the world...