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An identifiable image feature or target with independently surveyed coordinates, used to georeference and constrain a photogrammetry model. A check point is withheld from the fit to assess reconstruction accuracy. Distribution across the site, accurate survey and consistent height datums matter as well as the number of points.

A photogrammetry workflow jointly estimating camera geometry and scene structure from many overlapping images, commonly followed by dense surface reconstruction. Ground control points or accurately surveyed camera positions establish scale and georeferencing. Independent check points test accuracy rather than participating in the fit. A fine image ground-sampling interval does not alone establish equal vertical accuracy.