[mapserver-users] Finding the centroid given the feature

[Varun saraf]

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/testMap.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