7.5.2. Raster to vector

As the name of this function suggests, a polygon layer will be created according to the different raster values (contrary to the function Contour demonstrated in section, which creates a line vector layer based on raster grid values).

  1. Go to Raster.
  2. Select Conversion.
  3. Choose Polygonize (Raster to vector).
  4. Choose the newly created raster from the previous section (7.5.1.) and convert it back to a vector file (so specify an output shapefile, see Fig. 93).
  5. Start the conversion by clicking OK.
  6. Open the newly created shapefile.


An attribute field containing the former raster values will be created.

Beside the fact that the geometry became coarser (the boundaries are no longer smooth), we see that many of the original attributes have been lost (e.g. as seen with the Identify tool or within the Attribute table).

Fig. 93. Raster to vector conversion using QGIS.