Hello, I'm having a look at the paper. It looks interesting but it is not yet the "for mere mortals". Thanks.

Hello, tx for the reply. My interest is practical. I want to implement a computer program that checks the isomorphism of two planar graphs. I am currently using a general purpose library for this but it is "slow" (rather "too" slow). My idea was to profit from the case I have a planar graph and speed this up. Since I build up sets of graphs, having a "signature" would greatly reduce the number of graphs I have to "compare" with. I currently use the edgecountlist but the buckets get too big for larger vertexcounts. I will look into your suggestions.