I need to clip a large shapefile (600,000 KB) to another smaller shapefile (10 KB). The vector -> geoprocessing -> clip command is taking very long. Answers to similar questions say to use "ogr2ogr" but I am not sure where to start in installing ogr2ogr. I have no Python experience either, not sure if that makes a difference.
QGIS – How to Clip Very Large Shapefile Using ogr2ogr
clipogr2ogrqgisshapefile
Related Solutions
Rasters to the rescue! You can do this operation by converting your shapefile to a raster, doing the 'invert' operation and convert it back to vector
- Raster -> Convert -> Rasterize. Output layer raster1
- Open field calculator, enter expression raster1@1 = 0
- Raster -> Convert -> Polygonize, Output layer ocean_polygons
- Open Attribute table, search for DN = 0, toggle editing, delete selected features and save. What you will be left with will be polygons for the ocean areas.
Here is a rather simplistic answer because looks like you have tried quite a lot of optimizations, but thought I should mention WMS and Tile Cache here.
If you import your shapefile into a spatial database like PostgreSQL with postGIS, You could use something like GeoServer or MapServer on top of the database table to generate a WMS Layer. Now using SLD (WMS rendering rule format similar to xml). You can define rules to specify which polygons are to be rendered at what zoom levels (or other conditions). Even if you wanted to display all polygons in one go, your WMS will sure take a long time to render , but you can use it with something like GeoWebCache (comes bundled with GeoServer), to cache the tiles so you can boost your performance.
You can then overlay this WMS layer on top of Google Maps.
**Updates based on your comments
Some good links to start with are:
This should get you started. Let me know if you get stuck at something specific. Hope this helps you get a solution.
Best Answer
On windows environnement, if you installed Qgis with OSGeoW setup you have access to a shell which can run directly gdal/ogr. to run a clic processing use this command
ogr2ogr -clipsrc clip_polygon.shp output.shp input.shpreplace output and input with your files name and their path.
If you need more details about OSGEOW have a look to this page