## 5 Summary and Conclusions  
There is an important and current trend in various mapping agencies: the scanning of historical aerial photo collections for archival purposes in order to preserve them, make them available to a wider audience, and protect these materials from damage or loss of their properties due to aging or poor storage conditions.  
This article aimed to analyze the results of aerial triangulation and dense image matching in the context of comparing two scanning instruments: a Leica DSW 700 photogrammetric scanner and a consumer-grade EPSON V750 PRO scanner. The test area was the area of Warsaw's Gluzewiec district, with 38 large-format images acquired with a Wild RC10 analog aerial camera in May 1986.  
The authors verified and reported with visual and numerical examples how the scanning method affects the use of photogrammetric data and what recommendations should be followed for mass scanning and archiving of analog aerial photographs so that photogrammetric processing can use data with the highest possible quality. The research practically showed how geometric and radiometric resolution of scanned analog data affect aerial triangulation and dense image matching.  
It is recommended to use photogrammetric scanners to obtain the highest possible accuracy from historical aerial blocks acquired for mapping purposes. Therefore, the use of low-cost consumer-grade tools in the scanning process of historical aerial images can significantly reduce the extraction of all geometric information hidden in an aerial analog film. Results show that a consumer-grade scanner provides less qualitative data, affecting the accuracy of the resulting products than digital copies made with a photogrammetric scanner. Consumer-grade scanners should not be recommended for detailed surveys; however, their application in 3D products makes it possible to accept a much lower quality of the final products, such as point clouds, DSM, DTM and orthophotos. Most of the errors are caused just in the initial steps related to interior orientation and aerial triangulation. To mitigate the impacts of certain distortions caused by a consumer-grade scanner, it is worth using photogrammetric software that performs a camera self-calibration, which ensures the removal of specific residual errors.  
Considering future research, it is necessary to study the errors introduced at the scanning stage using different types of film and material. It would also be advisable to further investigate multi-epoch bundle block adjustment processing [51; 52]. Moreover, other DIM algorithms could be tested, evaluating how errors in the generated point clouds vary according to the land cover and land use types (e.g., forests, farmland, etc.). Photogrammetric archival data have enormous potential for the analysis of human impact on the natural environment. Automatic analyses of derived digital elevation models and orthophotos provide the opportunity to conduct interesting multi-temporal considerations. However, the accuracy and proper processing of archival materials is the first and key stage of their processing.  
Conceptualization: A.K., W.O., K.B., E.M.F., L.M. and F.R.; methodology: A.K., W.O., E.M.F., L.M. and K.B.; investigation: A.K., W.O., E.M.F. and L.M.; resources: K.B. and F.R.; data curation: [PERSON], W.O., E.M.F. and L.M.; writing--original draft preparation: [PERSON], W.O., E.M.F., L.M., K.B. and F.R.; writing--review, and editing: [PERSON], E.M.F., K.B. and F.R.; visualization: A.K.; supervision: [PERSON] and F.R.; project administration: K.B. and F.R.; funding acquisition: K.B. and F.R. All authors have read and agreed to the published version of the manuscript.  
The activities were partly funded by EuroSDR.  
Not applicable.  
**Data Availability Statement:** The raw data supporting the conclusions of this article will be made available by the authors on request.  
**Conflicts of Interest:** The authors declare no conflicts of interest.