
How to Infer Topology - jashkenas
http://bost.ocks.org/mike/topology?
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mbostock
A related tool I’m working on is a visual debugger for topology construction.
You can see an example here showing California state and county boundaries:

[http://bost.ocks.org/mike/topology/debugger.html](http://bost.ocks.org/mike/topology/debugger.html)

You can zoom & pan in the debugger as well as use the arrow keys to step
forward and backward through each step of the construction process, while in
the JavaScript console the global `current` gives details on the current step.
My plan is to make this a drag-and-drop interface for constructing TopoJSON
with the ability to see exactly what’s happening along the way. Of course, it
might also be nice to edit and fix the topology in-place, but for now that’s
probably better left to desktop GIS!

