Need an Algorithm to Determining Polygon Borders

Question

I'm currently writing a program in Java and I'm dealing with polygon objects. I want to create a different color border between touching objects depending on their class (i.e. land, ocean, etc). I need an algorithm for detecting which segments of my ocean border another ocean or land.

Right now I'm trying to do this by detecting which object share coordinates. And creating a total count of each class, and whichever class has the highest count, that is what that segment is bordering. It's too simple and doesn't work in about 40% of the cases, so I need something better.

Can any one recommend a different idea, or a source to look at?

Thanks in advance.

Answer 1

I would look at the GeoTools classes that wrap JTS geometries which provide you with a touches method - see http://docs.geotools.org/latest/userguide/library/jts/relate.html for a discussion of all the geometry relates methods,

Answer 2

If your spatial data can be converted to a Shapefile, you can explore various techniques such as buffer, intersection, clipping in the desktop application Quantum GIS. Once the workflow is finalized, you can code it using JTS Topology Suite, a Java API available from SourceForge. Also, you could script a simple solution with JEQL, a spatial script engine that runs on the JVM, using JTS.