On 10 Jul 2008 12:09:47 GMT, Robert Moore wrote:

Just to not confuse those that don't know, the yellow on the sectional
chart indicates the area that could be expected to be illuminated at
night by street lights, lights in buildings, etc. It is an aid to night
visual navigation.

I found a reference which doesn't state it that way. Mine you, this
reference just comes from a post in another forum, but he claims to quote
the map makers:

"The "yellow" area on the charts is supposed to correspond to developed
urbanized areas. The only significant change regarding charting in these
"yellow" areas involves the depiction of obstructions. Generally,
obstructions 201' and higher above the ground are depicted on the charts.
However in these "yellow" areas, only obstructions 300' and higher above
the ground are depicted.

Sincerely,
Rick Fecht
National Aeronautical Charting Office
Visual Chart Branch
301-713-2953 Ext-126"

Source:
http://forums.piperowner.org/read/7/21716/21731/quote=1

--
Dallas