Generation of High-Resolution Orthomosaics from Historical Aerial Photographs Using Structure-from-Motion and Lidar Data

This study presents a method to generate historical orthomosaics using Structure-from-Motion (SfM) photogrammetry, historical aerial photo-graphs, and lidar data, and then analyzes the horizontal accuracy and factors that can affect the quality of historical orthoimagery products made with these approaches. Two sets of historical aerial photographs (1934 and 1951) were analyzed, focused on the town of Woodstock in Connecticut, U.S.A. Ground control points (GCPs) for georeferenc-ing were obtained by overlaying multiple data sets, including lidar elevation data and derivative hillshades, and recent orthoimagery. Root-Mean-Square Error values of check points (CPs) for 1934 and 1951 orthomosaics without extreme outliers are 0.83 m and 1.37 m, re-spectively. Results indicate that orthomosaics can be used for standard mapping and geographic information systems (GIS) work according to the ASPRS 1990 accuracy standard. In addition, results emphasize that three main factors can affect the horizontal accuracy of orthomosa-ics: (1) types of CPs, (2) the number of tied photos, and (3) terrain.