[mapserver-dev] count points in polygon

[Steve Lime]

If you can't add spatial support you can still use your looping idea. Assuming you have
the point x,y in MySQL you can do a bounding box query against the points using the
bbox of each polygon (in MySQL). Then only do the "contains" test for those in that 
result set (in MapScript).

Steve

>>> On 1/19/2009 at 10:24 PM, in message <497551E9.5010100 at swoodbridge.com>,
Stephen Woodbridge <woodbri at swoodbridge.com> wrote:
> Mathias Tobler wrote:
>>   For a system showing dynamic species distributino maps I am looking 
>> for a way to count the number of points in each polygon of a polygon 
>> layer. I am using MapScript to dynamically add the points from data 
>> stored in MySQL. The polygon layer is a regular shapefile that can 
>> either be a regular grid or a shapefile of countries or regions. Due to 
>> the larger application this will be part of I am limited to MySQL and 
>> won't be able to use PostGIS or any other spatial database. I could 
>> probably loop through all points and polygon in MapScript and use the 
>> $status = $polygon->contains($point);  function, but considering that 
>> there can be 100'000 or more points this can get really slow. Is there 
>> any function that will do this?
> 
> I think I would recommend that you add a column to your points table and 
> then cycle through each point, determine what polygon it is in and 
> update the column with the polygon's uid. Then you can do a query like:
> 
> select polygon_uid, count(*) from points group by polygon_uid;
> 
> -Steve W
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