Hi Matthew Matthew Huck wrote: > 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 use GRASS for this sort of task. The basic steps are: 1. Import shape files using v.in.ogr 2. Set the region extents (a bounding box for the area of interest) using g.region 3. Make a vector to be used as a cutter - v.in.region 4. Select within the region box and cut on the boundary using v.overlay It's quite easy to roll these steps into a script and is definitely the way to go if you have to do this many times. Craig gdal/ogr devs, an ogr2tiles.py would be quite nice. _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
