Quick Building tracing question..

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Quick Building tracing question..

Michael Patrick
> 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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