I'm not really asking for a chunk of code to do this, but more of an algorithm I can work with myself.
For example, this is the state of Maine, obviously, and I have the points of each county stored as an individual polygon. I am looking to process all of those points in whatever way possible to end up with only the outer outline. Does having islands outside of the outline complicate things? Note: I know this is easy in QGIS but I need to be able to do it on the fly with a PHP script. Note2: Maine is just an example, I know state outlines are available elsewhere...I could have any number of counties from potentially more than one state. Any help is greatly appreciated! - Brandon
EDIT: This question differs from others in that it is absolutely necessary for it to be done in PHP code, and not in GIS editing programs. In addition, this problem is more complicated than simply generating a convex hull as concave contours are a definite possibility. I honestly have no idea where to even begin and am looking for someone with a little more experience with problems like this than I have.