TIFFs w/ overviews provide efficient performance as the 'overviews' are the result of the GDAL utility gdaladdo, which (basically) creates snapshots of the TIFF file with a lower resolution, based on the scale(s) you choose. So the TIFF draws quicker given a certain scale range, which eliminates the need to fetch the *actual* TIFF data at a, say, national scale.
So, a good option would be: 1./ use gdaladdo on each TIFF file 2./ use gdaltindex to create a tile index (shapefile) with file pointers to each TIFF 3./ reference the tile index shapefile in MapServer to display your TIFF data. Also, see Chris Hodgson's presentation from MUM3/EOGEO 2005 for more info: http://mapserver.gis.umn.edu/community/conferences/MUM3/present/session2/hodgsonppt/view ..Tom ________________________________ From: UMN MapServer Users List [mailto:[EMAIL PROTECTED] On Behalf Of Roland Martin Sent: 21 August, 2006 11:41 AM To: [email protected] Subject: Re: [UMN_MAPSERVER-USERS] Raster - TIF vs JPG "Tiled TIFF files with overviews pre-built are one of the highest performance ways of serving large raster images." From: http://mapserver.gis.umn.edu/docs/howto/raster_data/?searchterm=raster%20tiff Not sure what it means by 'overviews', though! Presumably JPG images require decompression prior to creating the output image, whereas TIFFs can just be read straight off. Cheers, Roland. On 21/08/06, Léveillé, James <[EMAIL PROTECTED]> wrote: Hi, I have about 4 000 georeferenced images. I can use either TIF (with overviews) or JPG format. Which one should I use with MapServer ? Which one offers the most performance ? Regards __________________________________________ James Léveillé Intélec Géomatique 420, boul. Charest Est Bureau 400 Québec (QC), Canada G1K 8M4 Intélec Géomatique: 418.687.5000 MTQ: 418.380.2005 (#227) -- Please note my new email address. Use other addresses at your peril.
