PostGIS documentation is horrible. I've read an entry for ST_ClusterDBSCAN multiple times, I've even tried in real world scenario. However I still got the feeling that I misunderstand
For example I've seen people using values as small as 0.1 in there. Doesn't that stand for like 10 santimetres? From the standpoint of my current understanding that doesn't make any sense, does it? How can, for example, 10 sm be a decent distance to cluster villages by? How can there be more than 1 village in such clusters?
Also bigger I make
eps slower the query runs and it's another thing that doesn't make sense for me. Why would that be a case?
And the last
eps related question is caused by the following quote:
An input geometry will be added to a cluster if it is either:
A "core" geometry, that is within eps distance of at least minpoints input geometries (including itself) or
A "border" geometry, that is within eps distance of a core geometry.
What's core geometry? Or what's border geometry? Since
eps is taken into account depending on the type of geometry.