Another alternative is to try a non-hierarchical binning approach. Use euclidian distances as a means of measuring distances between your grid, bin your distances in terms of distance between your important grids. Select the bin with the least travel cost, hopefully meaning it is optimized. You could use successive series of nodes to organize your moevments and help cut down on travel costs
in reply to Graph Traversal
Just do a web search on non-hierarchical analysis...
yet another biologist hacking perl....