[Mapserver-users] How does spatial filtering work with projections

[woodbri at swoodbridge.com]

Hi all,

I have a question regarding how spatial filtering works when a layer is
projected. Here is the scenario, We have lots of US image data that in
UTM zone projections and vector data the is in NAD83 degrees. The idea
is to use the vector data when zoomed way out to give the user a reference frame and then to switch to the image data when we can display it nicely using the UTM projection and overlay the NAD83 vector data using on the fly projection.

So if I'm zoomed into some small area of a UTM zone:

How does mapserver decide what shape files and or tileindexes it needs to look at? 

Does it look at the extents of the UTM extends as the superset of the area it needs to project? 

Does it project everything in the shape file to decide what to reject?

or probably something else all together :)

Thanks,
  -Steve W.