I have thousands of shapefiles with coordinates in lat/long (-180 to +180 x, -90 to +90 y), that contain polygons of which I wish to calculate the area.
I'm using the Python GEOS/OGR/GDAL API. If I call the Area() function for each geometry, I'll get the 2D area, or the area on a Mercator projection (basically). Since the polygons are really on a sphere, I want to convert them to an equal area projection before I calculate the area. I was wondering if anyone had any experience with this on here.
Some reading of the documentation suggested there were functions somewhere in OSRSpatialReference to transform a point or geometry from one projection to another, but it wasn't quite clear to me exactly how to use this or what projection to use.