[mapserver-users] Point inside or outside polygon???

[Paul Ramsey]

Yes, if things go according to schedule, you should be able to do exact
topological operations inside PostGIS before the end of the year, maybe
even as early as the fall. Combining PHP with mapscript with postgis
should allow some very complex web apps to be built with functionality
which was previous considered desktop-GIS-only.

P.

Norman Vine wrote:
> 
> Jan Hartmann writes:
> >
> >Yes, I understand that it can be impossible to identify a
> >unique polygon for
> >a point query, both in practice and theory. In that case,
> >however, I would
> >prefer to have both polygons returned to me, instead of just
> >one chosen at
> >random. At least I know that something IS indeterminate then.
> 
> Jan
> 
> I think that this is one of those attributes of a GIS that Mapserver
> doesn't necessarily try to do for 'performance' reasons, also there
> may be more then 2 poylgons sharing a point further complicating
> the solution.
> 
> AFAIK many GIS applications will not give a determinate answer
> for a simple point in poly request either,  however they will return
> a list of polygons intersected by another polygon.
>   i.e. a point with area
> 
> FYI
> I believe that there is work underway to include 'polygon algebra'
> functionality in PostGIS which will allow you todo this kind of query
> see
> http://www.vividsolutions.con/jts/jtshome.htm
> 
> Cheers
> 
> Norman

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     | Paul Ramsey
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