Horrible Looking WMS Raster Imagery

[Ed McNierney]

Jennifer -
 
You don't give us much information to go on, other than your dislike of
the results!
 
If you're consistently seeing poor-quality results, then there may well
be something systematic you're doing in your map files or MapServer
configuration.  I'm assuming you're using MapServer to generate these
"horrible-looking" images.  If you are, for example, requesting
low-color output from high-color images, you're going to see blotchy
output.  DRGs are low-color images (only 13 unique colors) so they are
not as prone to being affected by a low-color output request.
 
Could you provide an example of the map file and configuration you're
using to retrieve and display these images?  There's nothing special
about the WMS interface that inherently limits image quality - you can
get a perfect reproduction of the source imagery in many cases.
 
    - Ed
 
Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
Phone: +1 (978) 251-4242
Fax: +1 (978) 251-1396
ed at topozone.com 

________________________________

From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
Behalf Of Jennifer Zeisloft
Sent: Monday, January 23, 2006 10:00 PM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: [UMN_MAPSERVER-USERS] Horrible Looking WMS Raster Imagery


Greetings All,

We have been noticing that some (but not all) WMS raster images look
pretty terrible (extremely low resolution compared to what they should
be) when added to our MapServer application.  For instance, from
TerraServer (http://terraservice.net/ogcmap.ashx), USGS Digital Ortho
Quads are virtually useless regardless of scale, while USGS DRGs look
decent.  Daily MODIS imagery from NASA JPL World Map Service
(http://wms.jpl.nasa.gov/wms.cgi?) has also typically been a problem.
And there are others... 

I have recently been playing with GDAL to display our own rasters, but
also partially with the hope that it might somehow magically fix this
problem (of course it hasn't). 

I am wondering whether the display problem is local or if it is on the
data custodian's end, and whether this is typically the case.  Is there
any way to correct it?  If it is at the custodial end, what might be
done differently to increase the display resolution for WMS clients (so
that we don't make the same mistake)?

I really appreciate any hints or ideas you can offer.

Thanks much!

Jennifer Zeisloft
UW Sea Grant

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