[postgis-users] intersect operation in 3d?

Paul Ramsey pramsey at cleverelephant.ca
Mon Jul 19 15:26:35 PDT 2010

Your worldview is showing (don't be embarrassed).
If you're going to shell out "big bucks" for ESRI, why not shell those
bucks to the PostGIS development community (*cough*) and get the
feature you need added?

On Mon, Jul 19, 2010 at 3:14 PM, Hugh Stimson <hugh at hughstimson.org> wrote:
> 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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