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Author Topic: Aligning two overlapping sets of pictures (urban) taken one year apart  (Read 742 times)

lemieszek

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Hi all!

I'm studying the application of Metashape for urban studies and I'm trying to compare different properties of two sets of pictures of the same urban area taken 1 year apart from each other.

I've processed both separately using the same GCPs (I have maybe 30 of them but it's a huge area - 600 hectares). They mostly coincide to a great degree. If I measure the difference between DEMs I can see buildings that have been demolished or constructed and even how much the trees have grown or have been cut down.

But there are tiny differences that are a little bit annoying. If a given building (say, 20m high) hasn't changed but it's dislocated by a few centimeters from one set to the other, then the DEM difference will tell me there's a slice of height gain that's 20m high on one side and an equal height loss on the other side.

So my question is: is there a best practice regarding this kind of alignment process? Since maybe 95% of the area hasn't changed at all, one would think it's possible to align both of them perfectly, with maybe ever so slight variations on the remaining 5%, which wouldn't matter since that bit has changed anyway.

Thanks in advance!
« Last Edit: March 28, 2021, 09:27:43 PM by lemieszek »