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From Volker Mische <volker.mis...@gmail.com>
Subject Re: geocouch: limit number of points in an area
Date Sun, 01 Aug 2010 20:54:44 GMT
On 01.08.2010 22:48, J Chris Anderson wrote:
>
> On Aug 1, 2010, at 1:43 PM, Volker Mische wrote:
>
>> On 01.08.2010 17:24, Benoit Chesneau wrote:
>>> On Sun, Aug 1, 2010 at 2:17 PM, Volker Mische<volker.mische@gmail.com>
  wrote:
>>>> On 01.08.2010 10:53, Benoit Chesneau wrote:
>>>>>
>>>>> I'm looking for a way to limit number of points retrieved for an area
>>>>> depending on its size. Ie When playing with the zoom on the map I want
>>>>> to be able to only display and retrieved only main points instead of
>>>>> all the points in this area. Is there a simple way to do that actually
>>>>> ?
>>>>>
>>>>> - benoit
>>>>
>>>> Hi Benoit,
>>>>
>>>> there a two ways. Either introducing a "limit" parameter, but that's
>>>> probably not what you want. It would limit to a arbitrary selection (not
the
>>>> "main points" as you'd like to have it).
>>>> You probably want clusters. My suggestion is to do it on the client side
>>>> with OpenLayers' cluster strategy [1][2].
>>>>
>>>> [1] http://openlayers.org/dev/examples/strategy-cluster.html
>>>> [2] http://openlayers.org/dev/examples/strategy-cluster-threshold.html
>>>>
>>>> Cheers,
>>>>   Volker
>>>>
>>> This solution doesn't work when you have a lot of points though. Do
>>> you plan to add such things to geocouch ?
>>>
>>
>> Clustering isn't that easy. I think some layer on top of GeoCouch should/will be
built to handle such things. It can even be in any programming language and communicate with
GeoCouch via HTTP.
>>
>
> If there is a threshold that can be emitted with the points, maybe a _list function is
the way to filter it server side.
>

The problem is, that the points are potentially returned in random 
order. So you never know if there will be a point that is close to 
anther one at a later stage.

Cheers,
   Volker

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