[gdal-dev] Polygon area with intersection?

[Rudi von Staden]

Hi all,

I need to create a tool that will take a set of points (say in a csv 
file) given in WGS84 lat/long, and work out the area of the outer hull 
that encompasses the points. The points could be anywhere in Southern 
Africa.

I was thinking to use the following approach (using gdal/ogr and Python, 
since that's what I'm most familiar with):
1. write a function to return the outer hull as a polygon
2. clip to the four UTM zones covering the region (using Intersection())
3. reproject each sub-polygon to the appropriate utm zone using the 
CoordinateTransformation class
4. return the sum of the values returned by GetArea()

Is it necessary to break up the area into UTM zones to get an accurate 
area calculation? Is there perhaps an existing standalone tool that will 
do this in an easier way? Would it work using Python bindings for gdal 
and ogr?

Thanks,
Rudi