A write-only driver if I understand well ? There are not so many instances of
such drivers. I can think to the PGDump driver.
I have a write-only driver here: https://github.com/Oslandia/gdal_wasp
It's working but not complete, what I'll add in the next two weeks:
- unit tests.
- a line simplification option (probably Douglas–Peucker with
constrains to avoid contact with other lines)
- read functions in order to have a read/write driver.
Even if the driver is not complete at the moment and I'm not quite ready
to submit this contrib as a ticket+patch. I'd like to have
opinions/comments of those interested. Thanks.
That's certainly the trickiest part of your task. There's no such algorithm in
GDAL. I'm not very familiar with that but it sounds a bit like topological
processing. Perhaps PostGis topology could be used to compute the edges from
the polygons ? Reading the introduction of
http://postgis.net/docs/Topology.html, I can see that you should have in-
house competences on that ;-)
There's an idea for GSOC 2014 (Geography network support :
http://trac.osgeo.org/gdal/wiki/SummerOfCode ) that seems a bit connected with
your problem and could potentially served as the base for such algorithm.
But I'm not sure that GDAL alone could solve it. You likely need some
intermediate storage to store and retrieve the edges from the polygon set
(unless you have not that many polygons to deal with in which case in-memory
processing could be OK).
No, I won't have that many polygons, in-memory processing is fine.
Since I could not find an ogr interface to geos spatial index, the
polygon intersection is O(n^2), but thanks to bbox pruning it's only a
second to process typical input in debug.
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