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I have two shapefiles for Rwanda which have user defined projections. I am trying to clip the geology shapefile so that it has the same spatial extent as the districts shapefile. When I clip, I do get a saved file, but there are no data in it, the attribute table is empty as well.

Districts file has following:

Generated CRS (+proj=tmerc +lat_0=0 +lon_0=30 +k=0.9999 +x_0=500000 +y_0=5000000 +ellps=GRS80 +units=m +no_defs)

While geology file has the coordinate system:

G * Generated CRS (+proj=tmerc +lat_0=0 +lon_0=30 +k=0.9996 +x_0=500000 +y_0=10000000 +ellps=clrk80 +units=m +no_defs)

I am having trouble to reproject them so that they gave the same coordinate system but if I do so, I am not able to view them together.

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  • Can you add the extent of the layers, as reported by rightclick on the layer in the legend -> Properties -> Metadata tab?
    – AndreJ
    Jan 18, 2016 at 6:24
  • districts file- xMin,yMin 416917.07,4714211.43 : xMax,yMax 477602.01,4808194.74 geology file the extent is xMin,yMin 373418.04,9686146.92 : xMax,yMax 599790.44,9884288.67
    – sonali saha
    Jan 18, 2016 at 13:40

2 Answers 2

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I am not expert in qgis, but I would create a new empty shapefile specifying the same projections of the geology shapefile, then copy the districts geometries into that new shapefile and try clipping again the geology with the new districts in the same CRS. Also, when you do this copy and paste operation (hope it's possible in qgis but I guess it is), make sure the CRS of your project is set to that of the geology and the new shapefile, or you still will likely have problems.

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This task is a bit error-prone, because your CRS look similar. So QGIS might take the wrong one when adding a shapefile to the canvas.

Check the assigned custom CRS and layer extent for all layers in every step. The geology shapefile has to be reprojected to the district CRS, and the reprojected geology has to overlap the original district shapefile when OTF is switched OFF. You better remove the layers with the geology CRS before starting the clipping.

Your extents seem to look reasonable, with the geology layer (red) larger than the district layer (blue) (OTF still on):

enter image description here

The clipping layer has to be a polygon. You might use Vector -> Resaerch Tools -> Polygon from Layer Extent to get a good extent polygon. Clipping might fail if there is a topology error in the clipping layer you use.

Input layer is the reprojected geology, and Clipping layer the extent layer.

In my example, I used a highway layer downloaded from Openstreetmap.

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