WMS Server serving large raster

[Frank Warmerdam]

On 8/3/05, Milo van der Linden <mlinden at zeelandnet.nl> wrote:
> I indeed found the needed documentation on TILEINDEX and will try to create
> it with gdaltindex. My raster images are however overlapping, will this
> cause problems for the TILEINDEX since I think I remember that ESRI shape
> files do not support overlapping objects (MapInfo does)? 

Milo, 

There is no problem having overlapping objects in a MapServer tileindex.
Shapefiles do allow overlapping polygons.  I think you are thinking of 
Arc/Info topological coverages which do not (normally). 

Note that overlapping files will be rendered in the order they are processed
which is normally the order in the shapefile though it will be different if
you build a spatial index for the tileindex file.  The last file rendered "wins"
being drawn over earlier data.  
   
> Will the requested 100x100 image be rebuild with every request sent from a
> WMS client to the server? Because I tried it with a single Raster Image in
> MapInfo via WMS Server and zooming in and out resulted in a loss of raster
> quality because the raster remained in the resolution it had when it was
> first connected. 

I don't know anything about MapInfo WMS client support, but it sounds as if
it requests the view once and then just keeps showing that same raster.  As
long as your "smart phone" re-requests new images from the server they will
be at the requested resolution. 

BTW, 1.5GB of raster imagery is quite modest and not demanding of
MapServer.  However some additional performance related steps may
be useful.  If you are going to be making some wide area requests to
the server (say for an overview of all holland) you will find it helpful
to pre-build overviews.  This can be accomplished on individual files
using the "gdaladdo" utility.  

But with such a modest amount of imagery, my suggestion would be to
build a merged mosaic file with all your imagery.  This might be accomplished
with the "gdal_merge.py" script.  Make sure you create a tiled output TIFF
file (-co TILED=YES) and then build overviews on it with gdaladdo.  This
will give you one file to list in your mapfile, and maximize performance for
overview views.  Other approachs (ie. tile index with separate overviews layers
in the mapfile) are also reasonable but may be more work to setup.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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