Show settlement labels on a map based on population and settlement density in different areas

Question

Is it possible to show settlement labels based on population and settlement density in QGIS 3.36?

I have two layers of settlements:

Biggest Cities Layer: This layer contains the largest cities, which are always visible on the map.

Less Populated Settlements Layer: This layer includes smaller settlements, and I want to show these based on the following criteria:

• Population: Higher population settlements should always be prioritized.

• Area Settlement Density: In areas with many settlements, I need to hide even large ones (with populations of 100,000 or more). Conversely, in areas with fewer settlements, I want to display even small towns (with populations of 5,000).

Both layers use rule-based symbology (dot size based on population) and labels (text size based on population). I also need to show symbol only when label will be visible.

Is there possible way to achieve this?

Answer 1

You can create a field named "Settlement Category" and paste this expression , which will give 3 different ID's (0,1,2) based on your criteria.

~
case
when 0 <= "population" AND "population" <= 5 AND 0<= "DENSITY" AND "DENSITY" <=5 then 0
when 5 <= "population" AND"population" <= 10 AND 4<= "DENSITY" AND "DENSITY"<=10 then 1
when 10 <= "population" AND 10<= "DENSITY" then 2
END
~

The values 0,5,10 are indicated , you will decide the value boundaries.

In case that you dont want all of those 3 ID's to be at the same field, you can create 3 separate fields named for example "First Category" , "Second Category" , "Third Category" and paste at the expression of each one separately each expression. For example at the "First Category" field :

~
case
when 0 <= "population" AND "population" <= 5 AND 0<= "DENSITY" AND "DENSITY" <=5 then 0 END
~

etc.

Finally you will have 3 different fields where each one will have an ID based on your criteria.

Hope that helped (if i understood your question correctly).