Thanks for your reply Ralf.
Since posting my query I've found this helpful chart of functions with their
2.5d support:
http://postgis.refractions.net/docs/ch08.html#PostGIS_TypeFunctionMatrix
According to that, the ST_Intersects and ST_Intersection functions aren't yet
2.5d enabled. So I'm guessing that means that while they will accept data with
an assigned Z, as you suggest, only the x/y dimensions will be considered in
determining if they are coincident.
That isn't sufficient for the application I'm working on, I need to be able to
distinguish the case where one object passes over another one without actually
touching. The shapes involved are complex enough that using a simple elevation
rule to pre-filter can't account for all possible situations.
Might have to shell out the big bucks for an ESRI license. Ouch.
cheers, Hugh
Hi Hugh,
all functions in PostGIS will work on 2.5D data. So you have to add an extra
condition for your z-range.
Gr
Ralf
Am Freitag 16 Juli 2010, 23:32:03 schrieb Hugh Stimson:
Hi PostGIS folks,
I'm trying to find a way to read two 3-dimensional polygons and test if
they intersect. It's for a radar-bird-tracking application. I'm hoping
that PostGIS is a solution.
I've been scanning the Mailing list archives, and I gather that at least
some of the spatial operations which PostGIS provides are 3d-enabled.
Which surprises me, as my understanding was that PostGIS spatial
operations descend from the Java Topological Suite via GEOS, and JTS
advertises itself as being specifically for 2-d linear modelling.
Could I count on the ST_Intersects function to work with 3d data? Would
there likely be any special considerations for 3d?
http://postgis.refractions.net/documentation/manual-1.5/ST_Intersects.html
cheers,
Hugh
--
Hugh Stimson / 778.373.1024 / hughstimson.org
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