reprojection within map file does not seem to slow down performance within mapserver

[Frank Warmerdam]

John Mitchell wrote:
> Hi,
> 
> I have noticed that reprojection within a map file does not seem to slow 
> down performance within mapserver.  The mapserver documentation states 
> that if you have a different projection within the root of the map file 
> and a layer then it will take 2-4 times longer to reproject, but I have 
> not noticed any decrease in performance.
> Has anyone else had a similar result?

John,

Reprojection is not really terribly expensive, and whether doing it will
slow things down noticably or not depends a lot on circumstances.  For instance
reprojecting a layer with a hundred label points will not take long.  The
time to draw a label for each point will massively dwarf the time reproject
100 points.  But reprojecting a complex line layer with 100000 vertices
and a simple rendering style may take noticably longer.

I think the documentation comment is somewhat misleading, but in general
havig reproject on the fly will make things slower - anywhere from
imperceptibly slower to significantly slower.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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