* Erin Korris <ekor...@yahoo.com> [2010-12-27 16:02 -0800]:
> I am wondering if there is a rule to follow when tracing buildings using
> aerial
> imagery. On the default, Yahoo imagery, the buildings are slightly displaced
> so
> in addition to the roof you can see the foundation of certain sides of the
> building. Should this be ignored and the building drawn based on the roof?
Buildings should be drawn based on their shape and position at ground
level.[1] If the roof is flat, you can often just trace the roof then
drag the outline to where the building meets the ground. Otherwise, you
can usually see half the building's sides, so you can use those to get
placement for the outline.
[1] That rule of thumb works most of the time, but sometimes you just have
to use your best judgement. e.g. the Baltimore Convention Center's
second floor is narrower than its first, but the building is on a hill
and the increased width of the lower level is not apparent at one end
of the building because the second floor is at ground level.
--
...computer contrarian of the first order... / http://aperiodic.net/phil/
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