The orthophotos were prepared from archival aerial photos of the Białka valley taken in 1977, 1981 and 1994. As a part of this process, ground control points were measured with use of a digital orthophotomap with EPSG 2180 georeference system and digital terrain models (DTM), georeferenced in the same way. The accuracy of measurements was verified during aerotriangulation of the photos. To improve the methodology of archival photos orhthorectification, analysis of the accuracy of control points was made, indicating that it depends on the scale, the age and quality of the archival photos and the location of control points. It was found that the control points localized on such objects as pole bases, crossroads (meant as point of crossing of centerlines of roads), corners of buildings and crossings of the borderlines of parcels, provide sufficient accuracy of aerotriangulation and an exterior orientation, due to their unambiguous identification on the archival aerial photos and physical stability over the whole period during which the photogrammetrical flights had been undertaken.
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