We're using parcel data (polygon) to count student locations (point) based on parcel type. We're doing this using SQL and the ST_Intersects function.
It works great, except the City and County of Denver stores parcels with condominiums on them as multiple overlapping polygons, that is, each condo at a location gets its own parcel polygon - if there are 20 buildings on a parcel, there are now 20 coincident parcel features stacked on top of one another.
This is a problem because each parcel would count 1 student at that location once for every condominium parcel. So while there is only 1 student at that 'spatial location', if there were 20 condos at that location, that would be counted as 20 students.
Using a SQL 'distinct' does not seem to work...
How can we either:
a) Generalize the polygon data such that all overlapping polygons become a single polygon layer
b) Use some other SQL wizardry to eliminate the overlapping polygons from the query?