[postgis-users] degrees between points

[Nicolas Ribot]

> Thanks for your response. However, this is also not giving the answer I
> expect. As the input you show illustrates, this input gives a response of 45
> degrees, whereas the answer should be 90 degrees if 90 90 corresponds to the
> north pole and 0 0 a point on the equator. I have also tried this with a
> point 89 89 with a similar problem. A point 90 0 does however give the
> correct result of 90 degrees. Do I still have the wrong idea about what the
> function should do?
>

One important PostGIS feature is that the computations are done in a
planar, cartesian system.
Geodetic coordinates are not understood by postgis (except with the
*_sphere() or *_spheroid() functions)
We (at camptocamp) are currently leading a survey to estimate the
effort needed to integrate a geodetic support in Postgis, like Oracle
spatial does.

So the given result is correct to a planar point of vue, but wrong if
you consider coordinates on the earth surface.

Nicolas