We have discovered an interesting default behavior using WMS in ESRI ArcGIS software.  This is not really a 'bug', just the way ArcMap handles WMS requests.
 
By default, ArcMap will assign a 'background' color to WMS, which by default is white (255 255 255 pixel value).  There are a few of the new WMS (Baxter 2004, SPOT) that have clouds which have some pixels showing pure white (255 255 255).  Since by default ArcMap considers this the default background color, it renders all pixels that are pure white as transparent.  Thus you will see 'holes' in the clouds and can view whatever layers are underneath them, which makes for curious mapping!
 
A simple solution is to go into the layer properties, Advanced tab, and turn off the checkbox that makes the background value transparent.
 
MEGIS will go through and make this change on the LYR files we host on the WMS web page within the next few days.
 
This behavior is not apparent in other WMS clients tested including Google Earth, QGIS, and Gaia.
 
**********
Michael Smith
State GIS Manager
Maine Office of GIS
State House Station 174
264 Civic Center Drive
Augusta ME 04333-0174
(207) 215-5530
 
Member, Maine GeoLibrary Board

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