Mapfile Tuning

[Paul Ramsey]

We know from experience that the answer is "very expensive".  We had a 
large number of "init=epsg:" references in a mapfile and when we 
converted them to straight proj4 strings realized almost a second in 
speed improvements.

Frank Warmerdam wrote:
> Ed McNierney wrote:
>> I have not found that unnecessary projection definitions are expensive,
>> but I certainly agree that minimalist mapfiles will save you a lot of
>> time.
> 
> Ed, others,
> 
> I think a projection block that provides all the parameters should be very
> "cheap" in processing time, but any time you refer to projection details by
> EPSG code number, there is a whole file lookup involved.  As far as I know
> cost is paid for each EPSG reference, even if many places refer to the same
> code.  I would definately like to make some improvements in this regard,
> likely within PROJ itself.
> 
> It would be interesting to prepare some timetests on this issue to see just
> how significant it is.
> 
> Best regards,