[postgis-users] Projection for Calculating Area

[Robert Coup]

On 22/02/2008, Dylan Beaudette <dylan.beaudette at gmail.com> wrote:
>
> If you have really big shapes that are spanning multiple UTM zones, then
> setting up some kind of pre-processing logic which determines 1 of several
> possible albers equal area conic projections might work. For example, if
> the
> coordinates are near the continental US, use one set of standard parallels
> /
> central lon/lat to setup the projection. Adjust these parameters
> accordingly
> for different (continents?) regions of the world. You should be able to
> either find some existing EPSG codes which are close enough, or just make
> up
> your own, and define your projections in PROJ format. Then add them to the
> spatial_ref_sys table.


If your results don't need to be super-accurate, you could make the
simplifying assumption that the earth is spherical and calculate the area
accordingly - via something like http://tinyurl.com/2uhedb

Depends on what you're using it for.

Rob :)
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