[postgis-users] Projection for Calculating Area

Travis Kirstine traviskirstine at gmail.com
Thu Feb 21 09:33:17 PST 2008

We have been developing a web mapping application using google maps as
the front end interface with a postgis backend.  Using this
application the user can draw a bounding box in google maps and the
coordinates are then passed to postgis.  With postgis we then perform
a query on the polygons stored in the postgis database to return the
area using  ST_Intersection, ST_Transform (usually to UTM) and finally
ST_Area.  The application works great but the problem is  that since
we are trying to work on a global scale it is difficult to determine
what projection (EPSG) to transform the data to calculate an accurate
area since our data is in EPSG:4326 and returns decimal degrees.  We
can easily transform the query results to a UTM or a Albers projection
however the results can be inaccurate since the user may select
multiple zones or hemispheres when view the map at a global scale.  Is
there a accurate global projection for calculating area?

Travis K.

Toronto, Canada
"She knows there's no success like failure
And that failure's no success at all."
-Bob Dylan-

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