###### Abstract  
In the last decade, many aerial photographic archives have started to be digitized for multiple purposes, including digital preservation and geoprocessing. This paper analyzes the effects of professional photogrammetric versus consumer-grade scanners on the processing of analog historical aerial photographs. An image block over Warsaw is considered, featuring 38 photographs acquired in 1986 (Wild RC10, Normal Aviogon II lens, 23 \(\times\) 23 cm format) with a ground sampling distance (GSD) of 4 cm. Aerial triangulation (AT) and dense image matching (DIM) procedures are considered, analyzing how scanning modalities are important in the massive digitization of analog images for georeferencing and 3D product generation. The achieved results show how consumer-grade scanners, unlike more expensive photogrammetric scanners, do not possess adequate recording quality to ensure high accuracy and geometric precision for geoprocessing purposes. However, consumer-grade scanners can be used for time and cost-efficient applications where a partial loss of data quality is not critical. photogrammetry; historical; archival; aerial photos; aerial triangulation; image matching; scanner +
Footnote †: journal: Medical Imaging  
0000-0001-8891-2278][PERSON]  
0000-0002-233-1881][PERSON]  
0000-0002-3320-3330][PERSON]  
0000-0002-  
such as land use and land cover-LULC--studies, urban planning, flooding and environment monitoring, archaeological investigations, glacier changes, bomb crater detection, etc. [5; 6; 7; 8; 9; 10; 11; 12; 13]. Besides applying different physical protection methods (like encapsulating paper prints in envelopes) or experimenting with re-photography techniques [14], the scanning/digitization of historical photographs was identified as a preferable and permanent solution for preserving their content since the advent of the digital era. Indeed, with the beginning of digital photogrammetry in the 1990s, digital image processing became part of the photogrammetric practice [15], and the use of specialized photogrammetric scanners and ad hoc pipelines for aerial image digitization [16] started to be included in the photogrammetric processing workflow [17]. In Refs. [18; 19; 20] evaluated the quality of images digitized with regular/standard scanners as an alternative to professional solutions, considering that funds, hardware, and time restrictions for NMACs usually limit the number of analog photos digitized in their archives. Results showed that aerial photographs scanned by a non-professional scanner satisfy accuracy requirements for topographic mapping not better than the 1:5000 scale. Photogrammetric scanners, such as Leica DSW 700, Vexcel UltraScan 5000, Zeiss SCA, etc., were realized with linear or area sensors and designed explicitly for aerial imageries. They were born to ensure high geometric and radiometric accuracy in the analog-to-digital transformation process, besides performing, in many cases, also part of the photogrammetric tasks, like measurements of fiducials and the generation of image pyramids [16]. Fiducial marks are sets of physical marks generally positioned on the corners or edge-centers of aerial photographs that are useful for defining the reference for spatial measurements. The coordinates of fiducial marks [21], focal length, principal point, and distortion parameters for determining the interior orientation (IO) of the historical photographs are generally reported in the calibration certificates. However, this information is frequently missing for the oldest photographs, and a virtual reference system needs to be established for the pixel-to-image coordinates transformation [22; 23]. In the case of images acquired for mapping purposes with flights conducted under adequate weather conditions and stereo-coverage/overlap, the potential of their digitization is amplified by the possibility of extracting geometric information through photogrammetric processes [22; 24].