PostGIS: worldwide area calculation

Question

I have a table with polygons in EPSG 4326. These polygons are distributed all over the world, for example:

POLYGON((10.7324632658845 59.9253049236956,10.7331908150806 59.9244876816042,10.7342435821189 59.9247242537529,10.7335237442742 59.9255414900176,10.7324632658845 59.9253049236956))

Now I'd like to get the areas of these polygons in square meters. With ST_Area(the_geom) I get the area in square degrees, right? So I have to do something with ST_Transform. I got a good result for the above mentioned polygon with the following transformation:

ST_AREA(ST_Transform(ST_GeomFromText(the_geom,4326),31467))

However, the calculation (of course) fails when calculating the area of a polygon outside of the coverage of EPSG 31467 (Fatal error...).

Is there a "universal" area accurate projection for this purpose? Or do I have to check the location of every polygon and individually apply a suitable projection to calculate its area properly?

Answer 1

As alluded to in this previous answer, the ST_GeogFromText method will create a geography data type. This method expects your input data to be in 4326 (a geographic coordinate system) and measurements on this type are in meters. This will work world-wide. Here's an example:

SELECT
ST_Area(
    ST_GeogFromText(
        'POLYGON((10.7324632658845 59.9253049236956,10.7331908150806 59.9244876816042,10.7342435821189 59.9247242537529,10.7335237442742 59.9255414900176,10.7324632658845 59.9253049236956))'
    )
)

The 31467 projection uses a projected coordinate system that is only defined for a portion of Germany (and small parts of France, Austria and Switzerland). That's why you get an error when transforming data from another region into this projection (of course!).