## 2 Materials and Methods
### Data Sources  
The following data sources were used for the research: old military topographic maps, Corine Land Cover dataset, forest cadastral database, orthophotos, and LIDAR data (Table 1, Supplementary Materials). These data cover a period of 158 years. Figure 3: Karsuva forest: (**a**) the location of the former interstate border in Jurbarkas District, (**b**) a fragment of the Karsuva forest, separated by the interstate border. \begin{table}
\begin{tabular}{c c c} \hline
**No.** & **Data** & **Example** & **Data Source** \\ \hline
1 & Old topographic maps, 1860. Updated in 1865 & [[https://www.maps4u.lt/lt/maps.php?cat=20](https://www.maps4u.lt/lt/maps.php?cat=20)]([https://www.maps4u.lt/lt/maps.php?cat=20](https://www.maps4u.lt/lt/maps.php?cat=20)) (accessed on 1 January 2021) \\
2 & Old topographic maps, 1933–1940. Updated in 1938 & [[https://www.geoportal.lt/map/](https://www.geoportal.lt/map/)]([https://www.geoportal.lt/map/](https://www.geoportal.lt/map/)) (accessed on 1 January 2021) \\
3 & Old topographic maps, 1988. Updated in 1983 & [[https://www.geoportal.lt/map/](https://www.geoportal.lt/map/)]([https://www.geoportal.lt/map/](https://www.geoportal.lt/map/)) (accessed on 1 January 2021) \\
4 & CORINE Land Cover 2018, (CLC18_LT) & [[https://www.geoportal.lt/geoportal/nauijenos/](https://www.geoportal.lt/geoportal/nauijenos/)]([https://www.geoportal.lt/geoportal/nauijenos/](https://www.geoportal.lt/geoportal/nauijenos/)) -/asset_publisher/sUIF20 Ur705t/content/2018 -metu-corine-zemes-dangos-duomenu-rinkinys-juu-geoportal-lt (accessed on 1 February 2021) \\
5 & State forest cadastral data, 2021 & [[https://www.geoportal.lt/geoportal/valst/binemisku-tarmyba/savedSearchId=%7B5](https://www.geoportal.lt/geoportal/valst/binemisku-tarmyba/savedSearchId=%7B5) CA476B2]([https://www.geoportal.lt/geoportal/valst/binemisku-tarmyba/savedSearchId=%7B5](https://www.geoportal.lt/geoportal/valst/binemisku-tarmyba/savedSearchId=%7B5) CA476B2) -E876-4B39-A16B-C10 FDF4009B9%7D\& collapsed=true (accessed on 1 January 2021) \\
6 & Orthophoto maps, 2021 & ArcGIS Desktop (10.8.1, ESRI, Redlands, CA, USA) Basemap (Maps.lt orthophoto LKS) \\ \hline \end{tabular}
\end{table} 
Table 1: Data sources of forest areas from the 1 st half of the 19 th century to the 1 st half of the 21 st century. This paper uses maps from different periods, scales, and authors. It is therefore recommended to carry out a map uncertainty study prior to the research. Uncertainty analysis is difficult for maps from the 19 th and the 1 st half of the 20 th century. Fixed points, by which it would be possible to measure deviations in the representation of objects on maps, are questionable (surviving objects were selected for the orientation of the maps; however, for that reason, these points are no longer suitable for the study). The great socioeconomic changes that took place after the occupation radically changed the image of the area. There were large-scale deformations, collectivization, land reclamation, and people were moved from homesetads to settlements, homesetads vanished, and settlements were rebuilt. If a homesetad survived, the wooden huts were likely rebuilt due to wear and tear, possibly elsewhere. River beds were straightened in most cases. Roads changed their location in many places, some disappeared, and others were built anew, by laying asphalt or gravel surfaces, in places convenient for logistics. In order to carry out a high-quality analysis of the uncertainty of such maps, it is necessary to carry out a study of the history of individual places, verifying the material in the archives and interviewing older local residents about the geography of the preserved old objects of the area. The data on the map from the 2 nd half of the 20 th century are more reliable as most of the objects have survived. This topic is worthy of a separate study as it has been little researched. This is a problem for Eastern Europe because the Soviet occupation changed the pre-Soviet landscape considerably.