[Mapserver-users] raster image server: optimal performance

[Richard Greenwood]

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It's hard to add much to Ed McNierney reply, but I would emphasize the use=
=20
of image pyramids which can be created with gdaladdo. Color versus=20
grayscale will not make any difference if you use an 8 bit color pallet. I=
=20
use a single 200 color pallet for all my imagery (both color & grayscale)=20
this guarantees that adjacent tiles look similar and leaves 50 colors for=20
other purposes.

I've also had pretty good luck with ecw compression of grayscale images.=20
Unfortunately this is only an option on windows. The color ecw looked=20
pretty bad, but I expect we'll see improvements with 24 bit color in ms 3.7.

Rich


At 04:45 PM 1/23/2003 +0100, you wrote:

>Hello list,
>
>I want to use MapServer 3.6.3 as a raster server for rectified aerial=
 photos
>, working on a Linux box (SuSE 8.0), I have also gdal.
>
>For testing, I worked with a dataset of jpg's (plus worldfiles) or
>geotiffs.
>
>I have a test dataset of aerial photos (jpg plus worldfile, alernatively
>geotiff) of an area 40 x 25 km in 1km-square tiles with resolution 40
>cm, i.e. the tiles are 2500x2500 pixels, about 800 tiles.
>
>To get things working at all, I proceeded the usual way
>for raster images setting up an index
>shapefile (e.g. with gdaltindex). So far, everything OK ...
>
>
>Now I want to speed up things, as my original dataset covers 200x350 km,
>all in 40cm resolution. (IN jpeg 80 GByte, in GeoTiff about 400 GByte!),
>   in 1km-squares that would mean 70000 tiles. The files are stored in a
>simple file system.
>
>a) I tried out jpeg's vs (uncompressed) geotiffs. With the test dataset,
>jpegs (also diskspace-saving!) seemed to perform slightly better. Can
>anybody share the experience or give me hints about the best performing
>data format?
>
>b) What effect on MapServer response time does the tile size have? Any
>recommendations on the list for optimal tile size (bigger means less
>tiles) for best performance? Any dependencies on the data format?
>
>c) At the moment, I use b/w photos. What changes do I face in
>performance if I switch to color?
>
>
>Thank you
>
>Hubert
>--
>---------------------------------------------------------------------------=
----
>Dr.-Ing. Hubert Fr=F6hlich
>Bezirksfinanzdirektion M=FCnchen
>Alexandrastr. 3, D-80538 M=FCnchen, GERMANY
>Tel. :+49 (0)89 / 2190 - 2980
>Fax  :+49 (0)89 / 2190 - 2459
>hubert.froehlich at bvv.bayern.de
>
>
>
>
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>
>


Richard W. Greenwood, PLS
Greenwood Mapping, Inc.
Rich at GreenwoodMap.com
(307) 733-0203
http://www.GreenwoodMap.com=20

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