[postgis-users] Algorithm for Overlaying Areas and Features

[Renato Salas]

Hi group:

I'm curious about what is the underlying algorithm used to find out if a 
geo-feature is within an area.

For instance, I have a dataset with emergency calls and another with zip 
areas. Then I want to know how many calls are in each area.

I know I need to tag each feature with the zip area code it belongs to 
and then sum the number of calls for each area.

My question is, how do I determine in which area a particular call 
belong in an efficiente manner. Do I have to step in each area to find 
which features are inside its boundaries?. Do I first need to sort the 
features by Lat/Lon so that I know the boundaries of my features, thus 
reducing the number of candidates areas?.

I'm pretty sure this issue is well know and solved on the GIS community 
so please illuminate me since I don't want to reinvent the wheel.

Thanks all in advance for your comments,

Regards,

Renato