[OSM-talk] protocol for adding buildings using aerial imagery?

[john at jfeldredge.com]

Trying to estimate building height via the perspective in aerial pictures will be tricky, as buildings that were closer to the flight path won't show as much parallax as those that were farther away.

-------Original Email-------
Subject :Re: [OSM-talk] protocol for adding buildings using aerial imagery?
From  :mailto:frederik at remote.org
Date  :Tue Dec 28 01:32:16 America/Chicago 2010


Hi,

charlie at cferrero.net wrote:
> This is a major issue when tracing tower blocks - the taller the 
> building the more the roof appears to be displaced relative to the floor 
> due to the perspective of the plane taking the photos.  I have always 
> tried to map the base because, ultimately, a map is a representation of 
> what's at ground-level.  If you mapped roofs you'd get very tall 
> buildings overlapping the surrounding roads.

Sometimes I map the roof to get a good idea of the shape, then move the 
result to match the base.

It would be interesting to have editor support for estimating the 
building height depending on that displacement, or depending on the 
extent of the shadow - that would have to be calibrated for each imagery 
and location of course but so does the displacement of the whole image, 
and we're seeing people working on the latter...

Bye
Frederik

-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"

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John F. Eldredge -- john at jfeldredge.com
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