[Mapserver-users] Shapefiles and queries

[Steve Lime]

Hi Adam: MapServer takes a point an tests it against features within a
given layer. The logic is this (for a point selecting polygon query):

 - based on layer TOLERANCE values construct a spatial filter
(rectangle) to select candidate features with

Then for each feature:

 - see if the point is in the polygon, if in STOP
 - if not, compute the distance from the point to the polygon
 - if the distance is less that TOLERANCE, STOP

There are variations on this depending on feature types or if multiple
results are allowed. I the guess the point is that MapServer is not
using some type of approximation to do queries.

Steve

>>> "Adam Zornes" <zornes@athenic.com> 05/19/03 12:29 PM >>>
All,
 
            I am working on a project and am fiddling around with the
queries.  I realize that I know nothing about how mapserver processes
queries.  
            What I would like to know is how points are used in queries.
Say you have a point and a layer.  Does mapserver take said point and
look at each feature in the layer, calculating whether that point in
within each polygon and/or within a certain radius of the polygon?  Or
does is there merely a center point for each polygon, and proximity to
this point is used by mapserver?  
            Can anyone enlighten me on this matter, or direct me to a
source which will?
 
Cheers,
Adam Zornes

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