# From Analogue to Digital Photogrammetry: Documentation of Padise Abbey in Two Different Time Stages
## 5 Comparison  
The main and important difference between both processing are the datasets. The original images are digitized analogue images captured by a precisely manufactured metric camera and the images of the new survey are images captured by a non-metric camera, which is not designed for photogrammetric purposes. Due to the high cost of the images, just 12 images stored on glass plates were captured during the original survey. The average overlap on the object was approx. 5 images. During the survey in 2017, we captured 30 images and almost all objects are seeable on every image. During the new survey, we captured the images with larger GSD (avg. 4.8 mm/pix). This GSD is sufficient for determining if a stone was preserved or an outcome of the renovation. For processing \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & **X (m)** & **Y (m)** & **Z (m)** & **Euq. Dist. (m)** & **Reprojection Error (pix)** \\ \hline \multirow{4}{*}{**Control points**} & M1 & \(-\)0.001 & 0.001 & \(-\)0.001 & 0.002 & 0.8 \\  & M4 & 0.003 & \(-\)0.003 & \(-\)0.001 & 0.004 & 0.3 \\  & P1 & \(-\)0.001 & \(-\)0.001 & 0.001 & 0.002 & 0.4 \\  & P2 & \(-\)0.002 & 0.003 & 0.002 & 0.004 & 0.3 \\ \cline{2-7}  & RMSE & 0.002 & 0.002 & 0.001 & 0.003 & \\ \hline \multirow{4}{*}{**Check points**} & M2 & 0.003 & \(-\)0.005 & 0.005 & 0.007 & 0.4 \\  & M3 & 0.007 & \(-\)0.028 & 0.011 & 0.031 & 0.3 \\ \cline{1-1}  & P3 & 0.004 & \(-\)0.033 & 0.013 & 0.036 & 0.6 \\ \cline{1-1}  & P4 & 0.002 & \(-\)0.007 & 0.009 & 0.012 & 0.7 \\ \cline{1-1}  & P5 & 0.001 & \(-\)0.010 & 0.003 & 0.011 & 0.4 \\ \cline{1-1}  & P6 & \(-\)0.006 & 0.001 & 0.008 & 0.010 & 0.6 \\ \cline{1-1} \cline{2-7}  & RMSE & 0.004 & 0.019 & 0.009 & 0.0209 & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Differences on control and check points between measured coordinates from re-processing and adjusted coordinates from new survey. Figure 7: Distribution of control points (yellow) and check points (white). digitized analogue and digital images, we used the same method, and we processed the data in the same software. Even though both datasets were inherently different, we achieved respectable reprojection error (in both cases, RMS reprojection error is under 1 pix.). The comparison of datasets is presented in Table 5. The merged point clouds and difference in capturing scenario is presented in Figure 8.  
For comparison of different states of Padise Wall in 1991 and 2017, we generated a textured 3D model, point cloud, and orthophoto. The different states of the south wall are possible to examine and explore in these results. The easiest way to compare the state of the wall is orthophoto comparison. The orthophotos were overlayed on each other (Figure 9a) and the overlay was exported to.pdf format. This result is easily transportable, readable, and understandable for architects, conservators, restorators, and even for the wider public. On the overlay, it is easily possible to determine which stones of the wall are preserved after the renovation and which stones are the outcome of the renovation. From the  
Figure 8: Merged point clouds of the re-processing and the new survey. On the figure, it is possible to observe different capturing scenarios (the highlighted images belong to re-processing). \begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{2}{c}{**Re-Processing**} & \multicolumn{2}{c}{**New Survey**} \\ \hline  & Num. of images & 12 & 30 \\  & Distance from the object (m) & 8–19 & 18–39 \\ Images & F 35 mm equ. (mm) & 12.6 & 35 \\  & Sensor size (mm) & \(130\times 180\) & \(36\times 24\) \\  & Resolution (pix) & 11,717 × 16,441 & \(6016\times 4016\) \\  & Approx. GSD (mm/pix) & 1.3 & 4.8 \\ \hline Processing & Num. of tie points & 12,691 & 21,159 \\  & RMS reprojection error (pix) & 0.9 & 0.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison of datasets of the re-processing and the new survey. overlay, it is possible to create manually a drawing of stones of the wall with semantic information (Figure 9b).