[josm-dev] Layer processing tools

Lester Caine lester at lsces.co.uk
Thu Sep 27 12:24:29 BST 2012

I'm starting asking here as I know you will understand what I'm talking about ;)

OS Borderlines provide 9 layers with a different border on each layer. What I'm 
looking to do hopefully automatically is combine them into one 'layer'. The GIS 
tools I have found will not break down the shapes into 'line segments' which can 
then be combined to provide a base of unique ways which can then be recombined 
via relations to draw each of the different areas.

Things would be a little easier if all smaller shapes fitted inside the bigger 
shapes, but these are political boundaries so some smaller areas are in 
different bigger shapes for a different bigger boundary.

We then add the practice of using existing ways on the base map where they are 
available, but if these have not been created from the same way detail, then the 
clean way extracted from the dataset needs to be further broken up to use 
existing tracks where it can and add joining segments where it can't.

So what does JOSM already have that can be used in this processing? I'm assuming 
that 'merge nodes' would flatten a track that is identical between layers, but 
what happens when those tracks diverge? I get the impression that normal GIS 
practice would be to work with 'shapes' rather than the edge ways, which may be 
a way forward ... creating relations for the larger shapes using the smaller 
ones, but can that be made compatible with the OSM structure?

Lester Caine - G8HFL
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