[mapserver-users] Finding the centroid given the feature

[Varun saraf]

Center of the geometry works perfect. I need to get access to any
point inside the polygon feature. I believe I can use an itemQuery on
mapserver to query the attribute but how does mapserver return the
center point? Do I need to create an HTML template for that too?

On Mon, Jun 1, 2009 at 4:11 PM, Steve Lime <Steve.Lime at dnr.state.mn.us> wrote:
> 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
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>>>
>>>
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>