Clément, There is an optimized route for reprojection from 4326 -> 3857 in MapServer (see http://lists.osgeo.org/pipermail/mapserver-dev/2012-February/011956.html) so it can be very fast. I can't see how if could be faster than no projection. Perhaps the 10% is just within the margin of error? Or did you do the test 1000's of times and average the results? That might be what it takes to really see a difference.
Mike -- Michael Smith US Army Corps Remote Sensing GIS/Center From: Clément MONIER <[email protected]<mailto:[email protected]>> Date: Tuesday, December 4, 2012 7:23 AM To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Subject: [mapserver-users] Projection takes less time than no projection ? Resent-From: Michael Smith <[email protected]<mailto:[email protected]>> Hi All, I’m using MapServer to generate tiles to overlay on a GoogleMaps base layer. My data files are WGS84 shapefiles. So my current mapfile was looking like : MAP … PROJECTION "init=epsg:3785" END … LAYER … PROJECTION "init=epsg:4326" END … END … END I was wondering about improving response time by disabling on-the-fly projection. So I did pre-project my shp into spherical Mercator first. And my new mapfile now looks like : MAP … PROJECTION "proj=merc" "a=6378137" "b=6378137" "lat_ts=0.0" "lon_0=0.0" "x_0=0.0" "y_0=0" "k=1.0" "units=m" "nadgrids=@null" "no_defs" END … LAYER … END … END I do get the same tiles. But when asking a single tile using both mapfile, I noticed that the response time was higher (about +10%) when the second mapfile was used ! Do you have any idea about what’s going on ? Thanks & Regards Clément
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