[gdal-dev] WAsP map output for ogr

[Vincent Mora]

> 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.