When using the GDAL "Polygonize (raster to vector)" any values in the resulting vector layer is truncated to integer.

I have a raster showing windspeeds in squares of 500*500 meters, in the metadata-field i read that the lowest value is 2.5899999142 and the highest value is 12.6599998474. Then when polygonizing, the result layer only has values: 0, 1, 2, 3... and so on. No decimals.

I have googled the issue and found this: http://trac.osgeo.org/postgis/ticket/650 Don't know if it helps though.

2 Answers 2


Perhaps you could multiply your wind speed values using the raster calculator, by 10 if you want to keep the value to 1 decimal place, then export the result to polygon, add a new field to your polygon layer and use the calculator to populate its values by dividing the raster value by 10

  • 1
    Yes! I can verify that this will work! Thank you for your answer. I have to say though, that even if this will do the job, I think it is kind of a workaround and this should be fixed in a future update.
    – Patrik
    Commented Aug 12, 2013 at 11:26

There is a version now of gdal_polygonize that has an option to avoid rounding by using --float. I know this is an old question but these older versions of gdal_polygonize are still around. You should be able to replace the older version with the new one. Information is here :


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