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Author Topic: Orthomosaic Resolution/Pixel Size Issue  (Read 451 times)

Zeying

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Orthomosaic Resolution/Pixel Size Issue
« on: January 05, 2024, 06:02:54 AM »
Dear Concerned
I've been using Agisoft for some time now and I read related posts to find out that when building orthomosaic with mesh, the default pixel size is estimated from "Input Imagery Effective Resolution".
my question is:
1) For the geographic orthomosaic(top down view), does the calculated pixel size equals to GSD which is pixel size on ground. That would mean it's accurate on ground but if there's a really tall building in scene, the rooftop pixels will be inaccurate using that calculated value as an area of same size should take more pixels on rooftop than on ground.
2) When using planar projection to build facade orthomosaic using mesh, the calculated resolution value seems the same, I assume the value will be the same at any projection, how can I calculate area size on facade orthomosaic? like in top down orthomosaic I konw if I calculate the size of an area on ground using GSD it would be accurate, if on a rooftop it would be inaccurate using that same GSD.

I'm asking this because I'm trying to calculate area sizes of features on a 3D object using pixel number/pixel size of orthomosaics(I understand you can calculate accurately using 3D shapes in Agisoft, unfortunately this area size calculation work needs to be done on orthomosaic), and yet I realized that if the features are at different depth in the orthomosaic, it would be wrong to use the same pixel size value to calculate. I understand this concept in photogrammetry, but I want to know on both geographic/planar orthomosaics with agisoft calculated pixel size, at which level of the orthomosaic is that value based on.

Thanks in advance.
Zeying
« Last Edit: January 05, 2024, 06:36:15 AM by Zeying »