### Retrospective Photogrammetry: Examples
To achieve this, the project will collect complete primary data, i.e., maps, plans, photographs, and drawings, which are stored in digitized collections and represent (regionally, functionally, and architecturally) the basic regional house types of the territory. Within the framework of the Viskalia project, the Creation of the Virtual Open-Air Museum of Vernacular Architecture (VISKALIA) is planned [16]. Sometimes, the integration of historical and contemporary images is used to generate a 3D model. However, this approach only makes sense if the architecture of the object of interest has not changed over time. An example of such an approach is the Kronentor (\"crown gate\") object of the Dresden Zwinger. This object was reconstructed on the basis of archival and current images, which required subjecting the image repositories to a pre-processing analysis of their photogrammetric usability. Investigations are being carried out on the basis of a repository containing historical images of the Kronentor of the Dresden Zwinger [17]. As mentioned above, archival photographs can be used for multi-temporal analysis, including 4D modeling, which uses multi-temporal and historical aerial photographs to obtain spatial-temporal information for scenes and landscapes. Such images provide a unique source of data that, when combined with photo interpretation and reality-based 3D reconstruction techniques, can provide a more complete modeling procedure as they add a fourth dimension of time to the 3D geometric representation, thereby enabling urban planners, historians, and others to identify, describe, and analyze changes in individual scenes and buildings, as well as landscapes. Particularly important in this approach are historical aerial photographs that provide data about the past, which can be collected, processed, and then integrated into a database. The method proposed by [PERSON] [18] uses both historical (1945) and more recent (1973 and 2000) aerial photographs from the Trentino region of northeastern Italy to create a multi-period database containing information that will assist researchers in a number of disciplines, such as topographic mapping, geology, geography, architecture, and archaeology, when working to reconstruct building phases and understand landscape transformations. Archival photographs can be successfully used in archaeological work for photogrammetric documentation of sites. The idea is to be able to compare archival and contemporary excavations. Such a comparison often proves difficult due to the lack of detailed spatial information from previous fieldwork. In some cases, the only available documents consist of schematic drawings and imprecise field notes. An example is the inclusion of photogrammetry in the archaeological fieldwork of Middle Paleolithic sites in southwestern France (Combe-Grenal, Le Moustier, and Regourdou). The analysis of archival documentation with the inclusion of photogrammetric images proved to be helpful in decision-making during archaeological excavations [19]. Archival photogrammetric terrestrial photos can also be used in fields other than cultural heritage or archaeology. An example is the Omega project, which aimed to determine changes in the volume of Alpine glaciers over longer periods of time [20]. To this end, archival Numerical Terrain Models generated from topographic maps were verified against the original terrestrial photographs used to produce these maps [21]. Not only photographs but also videos can be used for the 3D reconstruction of buildings. An example of this is the use of historical film of Torino from 1928, despite initial concerns about processing this type of data. The experimental methodology used in the study allowed the quality of the results to reach an acceptable level, but the implementation of commercial software used for the Structure from Motion method may have been problematic.