## 2 Materials and Methods  
### Image Dataset and Reference Data  
The study area is located in the Warsaw district of Sluzewiec (Poland--Figure 2). This area was a former industrial part of the city that was converted into the new business center. It covers 5.765 km\({}^{2}\) and counts almost 640 residential buildings built between 1986 and 2012, which are mainly unchanged. Many production buildings were adapted (often partially) to new functions, with a large variability of shapes in a relatively small area. Figure 3 shows the test area, as visible in the orthoimages produced from the 1986 and the 2021 aerial datasets (Figures 3a and 3b, respectively). Figure 1: A view comparing the same image detail from a historical aerial picture scanned with the consumer-grade scanner EPSON V750 PRO (**a**) and with the photogrammetric scanner Leica DSW 700 (**b**). The 1986 analog images were acquired in May 1986 on a 23 \(\times\) 23 cm film with a Wild RC10 photogrammetric camera and a Normal Aviggon II lens (focal length of 213.75 mm). The block consists of 38 photographs acquired for surveying purposes in 5 strips north-south oriented, at the scale of 1:3000. The analogue photographs were scanned with a professional/photogrammetric and a consumer-grade/regular scanner with a resolution corresponding to a ground sampling distance (GSD) of 4 cm (Table 1). To properly georeference the archival images (Figure 4a), a GNSS RTK surveying campaign was carried out using a Leica VIVA GS15 receiver. The 3D coordinates of 154 stable-over-time ground points were acquired in correspondence with features (such as manhole covers) that remained unchanged over the last 40 years. Figure 4a shows the camera network derived from the 1986 aerial block while Figures 4b and 5 show the distribution and locations of unchanged points measured in the field. To improve the accuracy of GNSS, we used the precise satellite positioning system ASG-EUPOS (Active Geodetic Network-EUPOS). It is a project of a reference station system designed for Poland carried out by the Polish authority for geodesy-Head Office of Geodesy and Cartography. Figure 3: Aerial view of the Shuzewiec district in Warsaw with (**a**) the sub-block of 38 historical images acquired in 1986 and (**b**) the orthophoto from 2021. Figure 2: Test area in Shuzewiec district, Warsaw, Poland (highlighted red area). It is a part of the European Position Determination System (EUPOS). Using different observation methods, reference station systems can provide real-time corrections that are used by GNSS receivers in the field to calculate positions with better precision [46]. The accuracy of the 154 GNSS points measured in kinematic (RTK) resulted in 0.03 (horizontal) and 0.05 m (vertical). Among the available GNSS-based ground points, 44 well-distributed points clearly visible in the historical dataset (Figure 6a) were used for the photogrammetric aerial triangulation (AT) process (31 check points [CPs] and 13 ground control points [GCPs]). On the other hand, an airborne laser scanning (ALS) point cloud acquired in 2012 (Figure 6b) was used to assess the quality of the dense image matching (DIM) process with historical images (Section 3.2). The ALS data obtained with LiDAR technology has a density of 12 pts/m\({}^{2}\) and a vertical accuracy of 0.10 m [47]. The remaining 110 GNSS-based ground points were used for the vertical accuracy assessment of the DIM point cloud (Section 3.2.1). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Properties** & **Consumer-Grade Scanner** & **Photogrammetric Scanner** \\ \hline Scanner name & EPSON V750 PRO & Leica DSW 700 \\ Resolution (dpi) & 1800 & 1800 \\ Defined pixel size (\(\upmu\)m) & 14 & 14 \\ Average size (MB) & 1271 & 402 \\ \hline Camera & Wild RC 10 & \\ Date of the acquisition & 5–6 May 1986 & \\ Scale & 1:3000 & \\ Average GSD & 4 cm & \\ Focal length & 213.75 mm & \\ Format & 23 \(\times\) 23 cm & \\ Overlap & 60/40 & \\ Mean flying height & 682 m & \\ \hline \hline \end{tabular}
\end{table}