Matthew Huck kirjoitti:
Hi,
I've got a reasonably large shapefile that I wish to break down
into areas that match the topographic maps in NZMG. I've got a
python script that creates a shapefile with each topomap as a
polygon in it (and I can create a shapefile per topo map too if
required). What I can't work out how to do is to clip my master
shapefile by the smaller shapefiles. I've seen ideas of copying
across the features if they intersect with the clipping box, but
the data is contour lines so I want to "cut" the contour lines at
the boundry of the clipping boxes. Any ideas on the best way to
do it, I can get MapWindow to do it (sometimes, but it crashes
frequently).
I would use the GEOS function Intersection to clip to the box. Maybe it
would be easiest to import the data into PostGIS and do it there. It
wouldn't be too hard to write a GDAL script for the task either.
I did a similar job with road data of whole Finland in PostGIS and it
took a while but there were no problems due to the clipping.
Regards,
Ari
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