[mapserver-users] Finding the centroid given the feature

[Steve Lime]

Yes, you'd need to create a template for that. You could return JSON, XML, csv or whatever. This would
be the most straightfoward using 5.2 or ideally 5.4.1 (due out today) and the new style templates. You
could create a template output format to use like so:

OUTPUTFORMAT
  NAME 'geom_center'
  DRIVER 'TEMPLATE'
  MIMETYPE 'text/plain'
  FORMATOPTION 'FILE=geom_center.tmpl'
END

where geom_center.tmpl might look like:

<!-- MapServer Template -->
[shpmidx],[shpmidy]

and your query would look like:

http://.../cgi-bin/mapserv?map=foo.map&...itemquery stuff...&qformat=geom_center

Steve

>>> On 6/2/2009 at 12:17 PM, in message
<6db14d250906021017kb56f49ak36b4d0e4be417152 at mail.gmail.com>, Varun saraf
<vsaraf.gmu at gmail.com> wrote:
> 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
>>>>> _______________________________________________
>>>>> mapserver-users mailing list
>>>>> mapserver-users at lists.osgeo.org 
>>>>> http://lists.osgeo.org/mailman/listinfo/mapserver-users 
>>>>
>>>>
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>>
>>
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