Urban or not?

[Ronarch]

I wonder how the game knows if the area is urban or not. Because sometimes I use modded map and find not much of zeds even the area looks super urban (of course the distribution of zombie is set as "Urban focused"), meanwhile Zeds are having carnival everywhere in Mudraugh.

So does it require manual definition or there is a game mechanic to detect how many buildings there are to indicate how urban the area is?

[Axezombie]

Maybe I'm totally wrong but I guess the map maker is the one deciding which zones are urban, same with the forage zones