I'm trying to figure out what I can do with hierarchical topology. So far I understand (more or less) the construction of PostGIS topology and hierarchical topology, but I only have a vague conceptual idea of querying.
I have (want) a hierarchical organization of administrative areas: states (layer 3) and counties (layer 2). Counties are a child layer of states, both are multipolygons grouped by the county or state. I also have attributes for the minimum and maximum scale that individual faces can be displayed. This is a child layer (layer 1) of counties. ie, tiny coastal islands are not displayed at small scales. Can the attributes of child layers be seen from a layer? Or for my specific example, can I query for counties or states and only get the component faces (layer 1) where the query scale is within the min/max scale of the faces? I guess it would be like a dynamic topogeometry that is a subset of the static defined topogeometry for the layer. Maybe the query logic is backwards - instead, query the faces layer for the scale match, grouped by the parent layer of interest? With the topological relationship nature of topology, would I even need a hierarchical setup for this reversed query? ----- William Kyngesburye <kyngchaos*at*kyngchaos*dot*com> http://www.kyngchaos.com/ The equator is so long, it could encircle the earth completely once. _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
