[Tagging] Quick Building tracing question..

Michael Patrick geodesy99 at gmail.com
Thu Jan 10 10:56:00 UTC 2019

 > I've just traced what I can see as the visible roof area &  called it
> "building", as it's impossible to tell from an overhead image what is
> enclosed building & what is only a roof over an open area?
> If you had street-level imagery that may change things?

> As Graeme says - you cannot tell from satellite imagery.

Actually, you can, especially if you have imagery from multiple platforms
at different times of year, or better yet, different times of day.

Shadows are usually the primary clue. Partial obstruction of other objects
in the scene is another - like a semi-trailer truck poking out of a roof.
Pavement staining and tire marks from fork lifts. slopes of piles of
material along walls. Footpaths in snow., or if snow accumulates on the
roof. Stacked containers. If you have evening or night imagery, the light
silhouettes cast through windows to the outside. The presence of HVAC
equipment and ducting on the roof, and roof materials in general.
Obscuration or disturbance / distortion of vapor plumes from vehicle
exhaust or furnaces.

All this falls under 'aerial photointerpretation'. The ones I mentioned
above were from a WW II military training manual, some of the 'key' guides
now are thousands of pages long.

Michael Patrick
Data Ferret

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