MapServer templates can produce a center point for a geometry but it's not a true centroid but those aren't guaranteed to be "in" the polygon. MapScript could be used as well I suppose. In either case you'd send a lookup request to the CGI or MapScript, do an attribute query and return whatever you'd need.
Steve >>> On 5/29/2009 at 9:32 AM, in message <6db14d250905290732pb01747wce200eddfe73d...@mail.gmail.com>, Varun saraf <vsaraf....@gmail.com> wrote: > I am using mapserver 5.0 with google maps and the data source is the > US Census tracts as shape files and dbf files. > > On Thu, May 28, 2009 at 2:12 PM, Steve Lime <steve.l...@dnr.state.mn.us> > wrote: >> What version are you using? What data source? >> >> Steve >> >>>>> On 5/28/2009 at 10:01 AM, in message >> <6db14d250905280801q3660a6a7ycbcd5f5a238c5...@mail.gmail.com>, Varun saraf >> <vsaraf....@gmail.com> wrote: >>> Hi, >>> >>> I know mapserver uses a point-in-polygon method to find a feature >>> given a set of co-ordinates, but can it do the same thing reversed? >>> For example. Each polygon I draw has a number associated with it which >>> is in a "dbf" file with the same name as the "shp" file that mapserver >>> uses to draw the polygons. My current map file allows me to fetch that >>> unique number whenever I pass the co-ordinates of any point inside >>> that polygon (mapserver uses the point-in-polygon method to fetch me >>> the polygonID). The query I use is >>> >>> http://127.0.0.1:8123/cgi-bin/mapserv.exe?&map=C:/ms4w/apps/workshop-5.0/testMa >>> >>> p.map&mode=query&mapxy=-77.098617 >>> 38.87795 >>> >>> where mapxy keeps changing based on the user's click. The html >>> template I send just has the variable name [polygonID] which helps me >>> get the polygon ID of the point I specify in the mapxy variable. Now, >>> is there a way in which I can send this polygonID to mapserver and get >>> hold of any point (perhaps the centroid) inside of this polygon? Can >>> someone point me in the right direction here? >>> >>> Thanks a lot. >>> >>> -Varun >>> _______________________________________________ >>> mapserver-users mailing list >>> mapserver-users@lists.osgeo.org >>> http://lists.osgeo.org/mailman/listinfo/mapserver-users >> >> > _______________________________________________ > mapserver-users mailing list > mapserver-users@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/mapserver-users _______________________________________________ mapserver-users mailing list mapserver-users@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/mapserver-users