I have a table with column Catchment area (in km2), and I need to set symbol diameter based on that column. I need to get .sld file so I'm working with uDig.

I found out how to do it, but result is not acceptable because symbols are too big. There is not any normalization option in uDig or QGIS.


1 Answer 1


When scaling point symbols, it's good to scale them in a way that double value results in doubled symbol area (not diameter). Therefore, one has to use the square root of the value as a multiplicand.

While calculating square root, normalization can be applied at the same time e.g. using Field Calculator in QGIS.

The Field Calculator query would look like this. (Replace x with the biggest area value in your dataset.)

sqrt( area_field ) / sqrt( x )

You can then create Attribute-based point styles.


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