Count points not in polygon in QGIS (difference between points and layers give unexpected result)

Question

I have a layer of 130 points and another layer of driving distances as 6 polygon features When I use the count points in polygons I get a running total of the number of points in each polygon feature (as expected) with the largest number being 100

Difference

When I get the different of the same points and the polygon layer I get a layer containing more points than I expect (expect 30 but get 50)

Is difference the correct way to select points not in layer and what could be the reason for the inaccurate result (when I visualise the layer I don't see a symbol for each of the 50 points just an handful

Both the points and polygon layers are using the same CRS

Answer 1

If you want to just select points not in layer the easiest solution will be to use Select by location between your polygon and point feature. Just make sure you select from point layer not polygon. Then just invert selection. Difference is more for invert polygon clipping then polygon vs points analysis.

You might also find usefull this links:

• Points inside polygon
• Select by location