How is the "Cache centroid" calculated?

Question

My Cache centroid is more north than my Most Northerly cache found.

So obviously it does not refer to average coordinates.

Is it possible that the centroid is calculated as 3-dimensional? So if I have something in Europe and in USA, the centroid can be even under the Greenland's surface.

Is that correct?

Comments

I have note seen the code but the definition of http://en.wikipedia.org/wiki/Centroid is probibly used.
They are referring to the average coordinate but not in a "flat earth" version but in the real sphere(oblate spheroid) version. There is no reason to give the equator and prime meridian any special status. With caches logged in Europa, Asia and the Americas you can get the centroid on the north pole

The calculation are not done in 3D space but in 2D.The coordinates space is the surface of the earth so you example will be on the surface of Greenland

You can never calculate with coordinates on earth as if they are on a flat surface(if the distance is not very small). One big problem is that one degree longitude is 111.320 km at the equator and 0 km at the pole.
On the earth, the sum of the angles of a triangle is not equal to 180°. se
http://en.wikipedia.org/wiki/Non-Euclidean_geometry

The interesting case it when two caches are logged on that are on antipodes. Like on on the north pole and on the south pole. The centroid quite hard to define but is probity a circle around the earth in this case the equator.

Answer 1

The centroid is calculated exactly like FindStatGen for GSAK does it, which uses the Centroid.gsk macro (for details, read the source code).

We have several times compared values with both FindStatGen and online services and seen that Project-GC gives more or less the exact same result as the services we have compared with. It may be some km/miles of, but there are many factors that can give a distance difference like that. It's rather small when considering a globe of 40000 km diameter.