[postgis-users] How to design a database for continents, countries, regions, cities and POIs?

[Sandro Santilli]

On Wed, Apr 11, 2012 at 11:47:02AM -0400, Jerry Carter wrote:

> I might have a geometry for a country and separate geometries for the
> next layer of administrative regions (e.g. states in the United States).
> But there are often minor differences in the polygons such that the
> polygon for the country is nearly but not exactly the union of the states.
> How is this handled?

In the topology model your higher layer will be defined by composition
of lower layer items. So you would only say that "United States" is
formed by all the countries. And for each country you would only list
the counties they are formed of. And for each county the parcels.
And for each parcel the primitive faces. And each face is defined by
its edges.

The only actual geometries involved in all of the above would be
the edge geometries. Not any other geometry. So there's no difference
because primitive elements are singletons.

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