Execution of "extraction" - "contours" in Qgis is impossible. The process never finishes, I stopped it after 35 min.

The contour extraction works for all other raster files. I have tried with copies and converted the format but nothing works.

I can find the contour folder and the shapefile of the created contour but when imported to Qgis they don't show anything.

Is there a way to find out if the raster is damaged, or what cause there might be to this problem?


It looks like your raster has some very odd low values associated with it:

enter image description here

These values are clearly not related to the rest of the data and they fall along the very edges of the dataset. Not even setting the lower value to 0 or copying the lower value into the additional No Data value seemed to work. It is almost certainly this that is causing the contour tool to fall over.

I managed to successfully contour the dataset by using raster calculator to eliminate values over 0 (you could set this to whatever you wanted) and then run the contour on this raster.

To do this:

Open the Raster Calculator and enter the code:

(Raster Name > 0) * Raster Name

This selects all raster pixels of value > 0 and sets their value to 1; then it multiplies this value of 1 by the original value of the raster. Values of <= 0 are set to zero and end up as zero in the final calculation.

Run the contour on the new raster that is created by the calculator - 5m contours calculated below:

enter image description here

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