I have a shapefile with around 19,000 points. Its basically export from a raster. No i need to extract polygons, by aggregating the points which have same value.The field who's value i am going to use for aggregation is dynamically calculated each time using the elevation of points. NOw i need to spit out polygons. How can I do that using GDAL? is there a utility to do it. Any other opensource solutions are welcome. I have ArcGIS which has a toolbox called 'Aggregate Points' but somehow licence for it is missing.
It sounds like you would like a convex hull, which is just a way of wrapping a border around like points. See the OGR reference.
Alternately, use the Minimum Bounding Geometry tool in the data management toolbox, which requires an ArcInfo license.
If you later need the polygons to cover then entire area, you can calculate Thiessen polygons from them.
Finally, this is also possible in R using the