[postgis-users] spherical calculations in PostGIS

[Bruce Raup]

Hello PostGIS users and developers,

What is the status of how spatial calculations are done (planar vs.
spherical) within PostGIS?  I have searched the archives of this list, and
found a message from Dave Blasby from 2001
(http://postgis.refractions.net/pipermail/postgis-users/2001-September/000331.html)
wherein Dave asked, "does anyone know of any open source software libraries
for doing calculations on an ellipse?"  Was one found?

I see that there is a function "distance_spheroid", but what about the
spatial operators such as &&?  If your data coordinates are geodetic
(lon/lat), is there a way to make the operators operate on the sphere?  I
don't need them to operate on the ellipsoid -- the sphere is good enough.
But I work with large (continental scale) areas, so the plane is not good
enough.

If a spherical calculation package hasn't been found, then one developed at
my institute (National Snow and Ice Data Center) may be of use.  See
http://nsidc.org/data/tools/spheres/

It's written in Java, but much of it has already been ported to C.

Thanks,
Bruce

-- 
Bruce Raup                                               Phone:  303-492-8814
National Snow and Ice Data Center, U. of Colorado, 449 UCB, Boulder, CO 80309
http://cires.colorado.edu/~braup/