[postgis-users] WGS84 to meters

[Robert Coup]

On Tue, Sep 9, 2008 at 3:14 AM, Nicolas Ribot <nicky666 at gmail.com> wrote:

> No for surfaces. You will have to project your data into a planar
> projection system to do so (UTM for instance). This thread may be
> useful in your case to find the correct UTM zone according to your
> objects coordinates:


Untrue, the maths is just a little harder! And you need to assume the globe
is a sphere (ala distance_sphere()):

If you're dealing with lat-lon "rectangles" you want something like this:
http://mathforum.org/dr.math/faq/formulas/faq.sphere.html#spherecap

If you're dealing with arbitrary polygons its a bit more complicated:
http://groups.google.com/group/comp.infosystems.gis/browse_frm/thread/af0401d07c3068b5?lnk=igtc


HTH,

Rob :)
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