Josh,

On 12/05/2011 07:29 PM, Josh Doe wrote:
I created a Python script to convert OGR supported files (Shapefile
and many others) to the polygon filter file format used by Osmosis and
other tools. It will optionally buffer and simplify polygons for you.
You can buffer point and line features to create polys as well.

I have something similar done in C but always found it too fragile to share:

http://www.remote.org/frederik/tmp/clipgen.cc

It takes a "relation/xxx/full" OSM as input, and writes out an OSM file again (which you can view/modify in JOSM then convert to poly).

The clou with this one is that it will buffer and simplify but it will guarantee that the original polygon is always fully contained in the result - i.e. it will never cut off an edge through over-eager simplification. This is done not by clever algorithms but by simply grinding through a number of buffer and simplification parameters until the desired result is found.

I have found this to work well for polygon generation, except the glitch explained here http://www.osgeo.org/pipermail/geos-devel/2011-May/005208.html. If you can solve *that* problem then I'll even consider installing Python.

Bye
Frederik

--
Frederik Ramm  ##  eMail [email protected]  ##  N49°00'09" E008°23'33"

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