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I am using QGIS. I would like to clip a raster precipitation layer using an admin boundary layer that is vector data. However the geoprocessing tools seem to be usable only for vector data. How can I clip this precipitation layer?

Thanks for any help!

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Did you really mean for "vector" to appear twice in this question? – whuber♦ May 23 '11 at 15:23
@whuber - not in particular...does it matter in this forum? – Kirk May 24 '11 at 15:05
I couldn't make sense of the question without changing one of the "vector" to "raster." I think I get it now: you are saying you think the geoprocessing tools are only applicable when all elements are vector data. The confusion was that you explicitly say the boundary layer is in vector format, and as that is the immediate precedent, it makes the question ambiguous. – whuber♦ May 24 '11 at 15:19
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I have the same problem as the original question - the clipping tool using the gdal plugin works, but it only clips in rectangles.....what if you need to clip it to something like a country border? – Matt Jun 14 '12 at 16:53

3 Answers

up vote 6 down vote

Install the GDAL plugin and then use the Clipper Tool.
enter image description here

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The "gdal tools" aka "raster tools" plugin is installed by default since qgis 1.5, if I'm not wrong. No need to install it manually. – Giovanni Manghi May 23 '11 at 18:57
I found that this tool adds a band to the raster. It uses the command dstalpha. – BWill May 31 '11 at 13:19
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As Pablo has written, Clipper Tool is the answer. In qgis 1.7.0, the name of the plugin is "GdalTools". The tools (along with the "Clipper" we're looking for) are added to the Raster menu after enabling it with qgis plugin manager. – amp May 10 '12 at 7:43
up vote 1 down vote

I'm not sure of how to do it in QGIS, howver you may use another open source GIS software such as GRASS or GDALWarp to clip your raster. See keymirror and geographika answers below.

Clipping a raster using a polyline or polygon

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up vote 1 down vote

if you interested with python, you can read a good doc. at GeospatialPython.com, here.

and clipraster.py source is here.

clipping

The Process

Clipping a raster is a series of simple button clicks in high-end geospatial software packages. In terms of computing, geospatial images are actually very large, multi-dimensional arrays. Remote Sensing at its simplest is performing mathematical operations on these arrays to extract information from the data. Behind the scenes here is what the software is doing (give or take a few steps):

  1. Convert the vector shapefile to a matrix which can be used as mask
  2. Load the geospatial image into a matrix
  3. Throw out any image cells outside of the shapefile extent
  4. Set all values outside the shapefile boundary to NODATA (null) values
  5. OPTIONAL: Perform a histogram stretch on the image for better visualization
  6. Save the resulting image as a new raster.

i hope it helps you...

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