## 3 Results
### Spatial Distribution of X, Y and Z Differences  
To observe the spatial pattern of the differences for individual coordinates, they were plotted for each VP and for all photogrammetric products produced (i.e., BBA, orthomosaics, and DSM). All plots (Figures 9 and 10) include the marked outlines of the rockfall areas. Figure 9 shows the spatial distribution of the difference values diffX, diffY and diffZ of respectively BBA_traditional and BBA_PPK methods. When observing the results of BBA_traditional, those differences appear to be randomly distributed through the rockfall areas, except for Krnica where larger diffX and diffY are concentrated in the central part of  
Figure 8: Frequency distribution of the Z coordinates differences at all three rockfall sites for DSM_traditional and DSM_PPK. Bar width is set to 0.01 m.  
Figure 9: Spatial distribution of the differences in X, Y and Z coordinates, calculated for accuracy assessment of BBA produced by the BBA_traditional and the BBA_PPK method. the rockfall area. BBA_PPK results show that at Krnica diffZ expressed larger differences in the southeastern part of the rockfall site, whereas, at the Mangart site, there was a systematic increase of diffX and diffY in towards the northwestern part and towards the southwestern part of the rockfall for the diffZ, which also had the largest values. The results for the orthomosaics produced by BBA_traditional (Figure 10, X and Y coordinates) showed similarity to the BBA accuracy assessment for X and Y coordinates. The spatial pattern and the difference degree were both similar for all rockfalls. For the orthomosaics produced by the BBA_PPK method, no spatial pattern was recognized for Kekec and Krnica, as they varied across the whole rockfall sites. At the Mangart location, larger differences can be recognized towards the northwestern part of the rockfall site. As for the DSM result for BBA_traditional (Figure 10, Z coordinate), Krnica rockfall was the only one that had larger differences in the central part of the rockfall while, for the other two, the spatial pattern of the differences could not be recognized. On the other hand, a systematic increase of differences for the DSM produced by BBA_PPK is present for Mangart, where the differences had larger values in the southwestern part of the rockfall site. The Kekec rockfall had larger differences in the central part of the rockfall, while differences are larger when moving in the southeastern direction at Krnica. Observing the spatial distribution of the differences in X, Y and Z coordinate between BBA_traditional and BBA_PPK, when assessing the accuracy of BBA, it is possible to recognize that larger differences were present at the Mangart location. For the X and Y coordinates, the differences were similar across the rockfall area but, for the Z coordinate, they increase in the southwestern direction. Kekec and Krnica had homogeneous differences across the rockfall area with only Krnica having larger differences in Z coordinate in the southeastern part of the rockfall area. Similar conclusions can be drawn for the accuracy assessment of orthomosaics, when comparing the differences in X and Y coordinates of VPs as obtained by using the BBA_traditional and BBA_PPK methods. The difference  
Figure 10: Spatial distribution of the differences in X and Y coordinates, calculated for accuracy assessment of orthomosaic produced by the BBA_traditional and the BBA_PPK method, and of the differences in Z coordinates, calculated for accuracy assessment of DSM produced by the BBA_traditional method and the BBA_PPK method. in BBA accuracy assessment is with the Mangart site, where differences were increasing in northwestern direction for both with X and Y coordinates. No spatial pattern could be recognized for the Kekec and Krnica rockfalls.