[mapserver-users] Finding the centroid given the feature

[Varun saraf]

I had my mapfile extent changed and it worked "Perfect". Thanks a lot
Steve. It was a great help!

On Tue, Jun 2, 2009 at 4:16 PM, Varun saraf <vsaraf.gmu at gmail.com> wrote:
> Thanks a lot Steve. I am able to use the itemquery to fetch the other
> attributes correctly but somehow, the center of polygon isn't working
> right. Its returning to me, the co-ordinates that are outside the
> bounds of the mapping application. All my data is in the actual
> geographic co-ordinate system followed by Google maps and it returns a
> latitude/longitude pair corresponsing to some place in Antarctica. Any
> idea on what might be wrong?
>
> On Tue, Jun 2, 2009 at 1:50 PM, Steve Lime <Steve.Lime at dnr.state.mn.us> wrote:
>> 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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>>
>