[mapserver-users] Finding the centroid given the feature

[Steve Lime]

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
<6db14d250905290732pb01747wce200eddfe73d1b2 at mail.gmail.com>, Varun saraf
<vsaraf.gmu at 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.Lime at dnr.state.mn.us> 
> wrote:
>> What version are you using? What data source?
>>
>> Steve
>>
>>>>> On 5/28/2009 at 10:01 AM, in message
>> <6db14d250905280801q3660a6a7ycbcd5f5a238c595c at mail.gmail.com>, Varun saraf
>> <vsaraf.gmu at 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 at lists.osgeo.org 
>>> http://lists.osgeo.org/mailman/listinfo/mapserver-users 
>>
>>
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