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Ben_on_Lemmy@lemmy.ml

Can I assume orthoimagery is the best for tracing buildings? (lemmy.world)

submitted 2 months ago by BitSound@lemmy.world to c/openstreetmap@lemmy.ml

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I'm trying to correct local buildings on OSM. I've noticed that some of the buildings were traced before according to one set of satellite images, but are off according to others. One of the options for a background while editing that I've got is called orthoimagery. Can I assume that that is the best set of satellite images for tracing buildings from?

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[–] Balooog@discuss.online 5 points 2 months ago

Short answer: yes

Pretty much all of the imagery options available on ID are orthoimagery, since that just means it's been corrected to remove distortions from camera angle, lens, and topography.

Unfortunately, that doesn't always make them perfectly accurate. The only good way to check if a particular dataset is accurate is to record GPS along a feature identifiable in the imagery and check out the offset.

Usually the best one to use is a more local survey that covers just the city (usually only done for larger cities). Also ones where the area you're tracing has a more "overhead" camera angle (hard to trace when the top of tall buildings are very offset from their base).

I think the RapID editor automatically provides a few additional local imagery sets, depending on where you are working.