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I use QGIS 2.18.14 I import csv file with hits on a certain area. I then create a simple indicative heatmap (properties > heatmap).

Can I add contour lines to this heatmap and if yes, how?

I also put a vector grid on these hits > count points in polygon and then via properties > graduated based number of hits per square.

Can I add contour lines to this square based heat map and if yes, how?

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It is possible to simply add contours to a raster image via the Processing Toolbox -> Contour (Under GDAL Extraction). Here is an example: Input Raster Image created from point layer using QGIS HeatMap Plugin : enter image description here

After running GDAL Contour (Interval between contour lines = 1, keep the rest as is):

enter image description here

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  • Thanks! That is what I was looking for! Is there a way to make the contour lines match the categories of the heat map? – stijn geldof Jan 31 '18 at 14:48
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    Well, the heat raster layer you created contains continuous data, so the data itself does not contain any categories. The default way to control the 'categories' of the contour is the interval parameter aforementioned. However, if you'd like to override and create categories manually, you can add them under 'Additional creation parameters' and write "-fl 0.5 1 2 3 4 5 6 7 8 9", for example. – 15Step Jan 31 '18 at 15:03

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