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I'm trying to create a heatmap on QGIS 3 from a layer based on a 20,000-entry CSV file with longitude and latitude values, using EPSG:4326 as the CRS.

The layer itself looks fine, the markers are where they're supposed to be and whatnot, but I'm having trouble creating a heatmap that makes any sense. I suspect it has something to do with the radius being in degrees, but it won't let me change it to meters or anything else.

There's an alert symbol next to the radius input, and hovering over it displays "Distance is in geographic degrees. Consider reprojecting to a projected local coordinate system for accurate results." My understanding is that 'on-the-fly' reprojections are enabled by default on QGIS 3, and I'm just sort of stumped as to what exactly I'm supposed to do at this point to get an accurate heatmap.

Anyone have any ideas?

  • If it's not super important that your radii are exactly the size you want, just use a very small number of decimal degrees for the radius input. See here for info on converting distance to decimal degrees. – csk Oct 9 '18 at 20:30
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you can

Consider reprojecting to a projected local coordinate system for accurate results.

.... On the fly re projection is for display purposes only, so any processing you do will use the layer projection and corresponding unit.

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    To elaborate on this answer, you would need to export your CSV layer. In the Layer Panel, right click on the layer name > Export > Save features as... > choose a local projected CRS for the export. – csk Oct 9 '18 at 20:24

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