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In QGIS, I have data consisting of 4 fields (columns): "Date", "Long", "Lat", "Uncertainty Radius (UR)". While the latlong plots look good, I need to provide a proportional uncertainty radius (margin of error) with each coordinate. Not every coordinate has a different UR, but most are different, and it needs to be reflected on the map.

I downloaded the Visualist plugin, which has proportional symbols. However, when I apply it, it's giving me a proportionate circle according to how many times that specific coordinate is in my table (which I don't need). I need the "bubble" to read the UR for that particular coordinate it's associated with for that particular date. Some UR are 5000m and some are 28m. Each row of latlong and date has its own UR.

I can't find any other plugins for QGIS that will do this. How can I visualize this? Am I using the Visualist proportional symbol incorrectly?

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  • 2
    Buffer using the UR field as the distance Commented Jun 9, 2025 at 7:49
  • I tried but get one color completely covering the map. I don't understand why Commented Jun 25, 2025 at 1:36
  • Probably because your data is in decimal degrees and UR is in meters. Commented Jun 25, 2025 at 5:43
  • Yes. I've looked into it and I'm trying to match the CRS's but it doesn't seem to fix. Side note: the answers below aren't accurate. I see circles on my map which appear to be the correct size of my UR, but when I compare the measurement to a manual Google Map measuring tool, the qgis circle is smaller by about 5%. Commented Jun 25, 2025 at 21:05
  • QGIS measurements are more accurate than Google Maps. Commented Jun 26, 2025 at 4:59

2 Answers 2

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There's several options alreadly included in QGIS. As user2856 mentioned you could run the buffer process and choose the UR-field as distance. This will create polygon features.

If you want to keep the data as points, you can choose to override the symbol size directly. Change the symbol size to meters at scale and click the data defined override button right next to it. Choose the UR-field to override the symbol size. If some points don't have UR-values this code takes the base value (2m in my case) for those and the UR-value for others. Input the following in the expression builder after clicking Edit

CASE
WHEN "UR-Field" IS NOT NULL THEN "UR-Field"
ELSE @value
END

Data defined override

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You can add an additional symbol layer to your point. Click the +, and add a Geometry Generator symbol layer.

Change column1 to your distance column name.

boundary(
 buffer(
  geometry:=$geometry, distance:="column1"))

enter image description here

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  • I tried this method but no boundary/dashed symbols appears. The dot in the middle is there but that's it. I made sure my settings matched your formula and what I see in the picture, but I don't see the dashed circle. That said, when I chose "point/multi-point" as the geometry shape, it works. But it has a weird look to it. I prefer the dashes. So why is multi-point working but not multi-line? Commented Jun 13, 2025 at 3:12

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