# Developing a GIS Model for Identifying Bear Corridors with Open-Source Data: The Romanian Context
## 2 Materials and Methods
This dataset provides detailed three-dimensional representations of Earth's terrain, making it a cornerstone in spatial analysis research. With resolutions ranging from 30 m to 90 m globally, and enhanced versions available for specific regions, the SRTM DEM offers flexibility for a wide array of applications. It has become an indispensable tool in fields such as cartography, hydrological modeling, terrain analysis, and infrastructure planning. The accessibility and accuracy of SRTM DEM data have also enabled their extensive use in natural hazard assessments, environmental monitoring, and land-use planning [29; 30; 31]. Its availability as a public resource has cemented its role as a fundamental dataset for both scientific investigations and commercial developments, significantly advancing spatial analysis capabilities worldwide. In our case study, the DEM was singularly analyzed based on the following classes: 0-500 m (7 points), 500-1000 m (1 point), 1000-1500 m (1 point), 1500-2000 m (4 points), and greater than 2000 m (8 points). The score obtained by areas with lower altitudes can be explained by the interconnection of this abiotic factor with the other factors that condition the vegetation structure and its abundance as a rank 1 factor and, in complement, with herbivous consumers as a rank 2 factor, the two factors representing the trophic base necessary for the existence of the species. In particular, the pedo-ecological conditions in the altitudinal zones between 0-700 m favor the development of a greater number of grass species, trees, shrubs, etc. and in a much larger quantity and with a wider spatial distribution than in the zones located at altitudes above 2000 m, where the limiting factors represented by climatic conditions  
Figure 2: Methodological flow-chart. greatly restrict the above-mentioned characteristics. All this, together with the increase in the number of bears in our country and the need for the species to expand its habitats, creates a favorable framework for the use of habitats at low altitudes. Considering the restrictiveness and favorability by induced slope, the analysis of slope as a favorability factor is based on its classification in two classes: \(<\)12 degrees (10 points), \(>\)12 degrees (1 point). The slope is closely linked to another determining factor in the ethology of the species, namely the landform, which is decisive for the existence of places necessary for winter sleep. Thus, the rugged relief with slabs and caves favorable for winter roosting is found on steep slopes, this factor being a determining factor in the habituation of the species. The digital database representing the cost raster was created by integration based on the weighted sum between databases that highlight the individual influence of favorable factors, including altitude, land use extracted from CLC, slope, the degree of afforestation, the distance from water sources, and restrictive factors, including the anthropic presence in the natural landscape such as the distance from settlements and the distance from the current and planned transport infrastructure (roads and railways). The distance to water resources was analyzed based on the calculation of the Euclidean distance on five classes as follows: 0-200 m (1 points), 200-500 m (3 points), 500-1000 m (6 points), 1000-2000 m (8 points), and over 2000 m (10 points). The distance to the water source can be a danger in terms of temporary rises in water levels caused by melting snow when the cubs are very young and particularly vulnerable, with flooding of the den being potentially fatal for them. The distance to the transport infrastructure was analyzed by categories of favorability, being classified as follows: 0-100 m (10 points), 100-500 m (7 points), 500-1500 m (4 points), and over 1500 m (1 point).