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Can anyone tell me how to crop a raster layer in QGIS? I want to make contours from a section of a layer, and including the whole layer will create far more data than I need and slow down the rendering.

I have found that I can do it by using the Raster calculator and specifying a new layer extent, but how do I know what values to enter for the rows and columns?

I also tried cropping the geotiff in Photoshop, but it seemed to lose the coordinate data.

Is there any way to create contours from part of a raster layer without having to crop it first?

I am very new to this, so it’s possible I’m missing something obvious. I’d appreciate any insights!

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somehow related gis.stackexchange.com/questions/10117/… –  nadya Dec 24 '12 at 3:18
    
Be careful whenever you crop a raster. If you crop to a non-multiple size you'll get unaccurate not-integer pixel size and it can get messy if you did not realized in time. –  user19416 Jun 24 '13 at 17:50
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1 Answer 1

up vote 6 down vote accepted

The Raster|Extraction|Clipper tool will help you to do this.

You can open the tool and then click and drag in the raster image to select the area you want to export as a new raster (Clipping mode: Extent), and then refine the exact coordinates in the Extent fields (if necessary).

Probably no way to do contours on only a selection of a raster; clip it this way first!

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Thank you! So easy! –  Graham vdR May 7 '12 at 7:37
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