I used zonal statistics through QGIS to assign raster image values to polygons.
Here, Raster image has value in range from 0 to 238.567.

As a result, some NULL values are assigned to polygons,
even though raster image fully covers those polygons.

When "count" is assigned to zero, statistical values are set to NULL. But such a polygon is still on the raster image(at least visually).

What's wrong with it ?

  • 1
    Did you try to zoom in map to cell with NULL value and get cell value from original raster ?
    – Shiko
    Apr 28, 2017 at 3:20
  • Yes, I've checked and cell value was not NULL.
    – Ichiro
    May 2, 2017 at 17:39

1 Answer 1


The problem here is likely that the polygons are too small with respect to the cell size. If you use the resample tool , and reduce the cell size this hopefully will work.

However, be careful when you resample, as some types of data will lose their original meaning. For example, population counts, if the original value remains the same after resampling, will be invalid, as the population for a given area will increase with respect to the change in cell size.

You can use: Grass resample.


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