I don't think a lot of experimentation is required, I would implement it
as such:
g = [view port width / cell size][view port height / cell size]
For each point, p:
px <- convert p to view port PX
px <- floor(px / cell size)
if px in g is valid and g[px.x][px.y] not defined:
g[px.x][px.y] <- p
for each cell in g, if defined:
render g[x][y] as marker
I'd run this on zoom end, and move end (after pan completes, or after
mouse button released)
The only configuration is the cell size, where 1 would mean there would
be at most 1 marker for a given pixel, and the values increase from
there. A higher value would mean better preformance, a lower would have
a higher density of points.
- Chris
alts...@yahoo.com wrote:
> I think the proper solution would be to limit number of markers depending on
> zoom level and visible map region. If you're at high zoom level and markers
> are too close to each other, they will overlap and you do not really see
> anything. Solution is to render not all markers but skip markers if distance
> between them is too close (probably distance should be determined by
> experimenting). When user zooms in, app should communicate with server and
> request more markers for visible region.
>
> opengts tracking system has the very same problem. I was going to implement
> something like I explained above myself but it's quite low on my priority
> list. But if you have the solution, I'd like to use it ;)
>
> Serg
>
>
>
> ----- Original Message ----
>
>> From: willson <talentp1...@yahoo.com.cn>
>> To: users@openlayers.org
>> Sent: Tuesday, April 14, 2009 12:26:40 PM
>> Subject: Re: [OpenLayers-Users] How to add many(>400) markers to the map?
>>
>>
>>
>>
>> Hi,
>> if you were using Geoserver and wms, dynamic symbolizer could help you.
>> Check the following out:
>>
>> http://blog.geoserver.org/2008/12/08/dynamic-symbolizers-part-1/
>>
>> - mika -
>>
>>
>> willson kirjoitti:
>>
>>> Hi,
>>> try to search mailing list for strategies, performance. I have the same
>>>
>> problem not solved yet. It looks I will have to render at server site.
>>
>>> Michal
>>>
>>>
>>> Hi everyone, this is the first post on this forum. I have search the
>>> problem
>>>
>> on the forum, but find no anwser.
>>
>>> What I need to solve is: I have more than 400 points need to show on the
>>> map,
>>>
>> these points query my db every 10 secs, and change their color according to
>> the
>> return value.
>>
>>> I use the openlayers.layer.marker to implement, but in ie the markers make
>>> the
>>>
>> map so slow when zooming.
>>
>>> Then I move to openlayers.layer.vector, but it's even slower than marker.
>>> Any suggestion in such "Adding large and dynamically changed markers"
>>>
>> situation?
>>
>>>
>>>
>>> hi, render in serverside(may be wms) can improve the performance much, but
>>> how
>>>
>> to make markers dynamically change color? Any solution?
>>
>>>
>>>
>> _______________________________________________
>> Users mailing list
>> Users@openlayers.org
>> http://openlayers.org/mailman/listinfo/users
>>
>>
>>
>> hi,
>> Yes, I am using geoserver and wms. I have look at the link, but it may be
>> not
>> the answer. Since the data in my db change frequently, and the marker need
>> to
>> reflect these changes. For example , I have a table, and a column named
>> "kpi",
>> when kpi<0.01, the marker's color is green, else is red. It may be not an
>> "sld"
>> issue.
>>
>> --
>> View this message in context:
>> http://n2.nabble.com/How-to-add-many%28%3E400%29-markers-to-the-map--tp2631715p2632376.html
>> Sent from the OpenLayers Users mailing list archive at Nabble.com.
>>
>> _______________________________________________
>> Users mailing list
>> Users@openlayers.org
>> http://openlayers.org/mailman/listinfo/users
>>
>
>
>
>
> _______________________________________________
> Users mailing list
> Users@openlayers.org
> http://openlayers.org/mailman/listinfo/users
>
>
>
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