speed of map generation

[Ben Madin]

G'day all,

We are generating a map showing relative densities in various  
polygons (worldwide adminstrative regions) of various commodities.  
This is being done using php-mapscript (4.8), by querying a SQL  
Server database, developing a range to code, and generating classes  
below. The shapefile does not have any of the data associated with  
it, only the id which matches up with that in the db.

When we do this at a country level (242 countries) there is little  
trouble with speed - maybe a few seconds.

However, at the next level (3300 administrative regions) this is  
taking way too long. Through various testing, the only step that is  
taking longer than 1 second is the

$img = $map->draw();

step, which can take upwards of 15 seconds - very tedious for a user.  
(Originally we tried it using reprojection (to orthographic) it was  
routinely taking > 3 minutes!, so sadly that has been dropped.)

I accept that the shapefile is large (90MB), and some time will be  
required, but this seems way to long. if we don't try to colour the  
polygons, the map displays very fast.

I have attached the class definitions for a part of the mapfile which  
is generated. The CLASSITEM is the polygon id. Any suggestions??

CLASS
       NAME "< 7040000 /sq km"
       EXPRESSION /^$/
       METADATA
       END
       STYLE
         ANGLE 360
         COLOR 0 204 51
         SYMBOL 0
       END
     END
     CLASS
       NAME "< 5280000 /sq km"
       EXPRESSION /^157$/
       METADATA
       END
       STYLE
         ANGLE 360
         COLOR 0 153 102
         SYMBOL 0
       END
     END
     CLASS
       NAME "< 3520000 /sq km"
       EXPRESSION /^158$|^162$|^163$/
       METADATA
       END
       STYLE
         ANGLE 360
         COLOR 0 102 153
         SYMBOL 0
       END
     END
     CLASS
       NAME "< 1760000 /sq km"
       EXPRESSION /^156$|^160$|^161$/
       METADATA
       END
       STYLE
         ANGLE 360
         COLOR 0 51 204
         SYMBOL 0
       END
     END
     CLASS
       NAME " 0 "
       EXPRESSION /^$/
       METADATA
       END
       STYLE
         ANGLE 360
         COLOR 0 0 255
         SYMBOL 0
       END
     END
     CLASS
       NAME "No Data"
       EXPRESSION /^$/
       METADATA
       END
       STYLE
         ANGLE 360
         COLOR 255 250 205
         SYMBOL 0
       END
     END


cheers

Ben	


-- 

Ben Madin
REMOTE INFORMATION

t : 08 9192 5455
f : 08 9192 5535
m: 0448 887 220
Broome   WA   6725

ben at remoteinformation.com.au





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