# Comparing PlanetScope and Sentinel-2 Imagery for Mapping Mountain Pines in the Sarntal Alps, Italy
## 3 Results
### Classification Results
ROC curves and AUC values of classification scheme 2 confirmed a similar predictive power of both models, and AUC increased to 0.96 for both PS + GLCM\({}_{\text{MAX}}\) and S2 + GLCM\({}_{\text{MAX}}\). For scheme 3, class separability for PS + GLCM\({}_{\text{MAX}}\) + Topo (0.96) and S2 + GLCM\({}_{\text{MAX}}\) + Topo remained constant (0.96). The ROC curves of classification scheme 4 showed a slightly better performance of PS + GLCM\({}_{\text{MAX}}\) + Topo + CHM compared to S2 + GLCM\({}_{\text{MAX}}\) + Topo + CHM, due to the lower number of false positive and the higher number of true positive pixels. Additionally, AUC indicated a minor improvement in class separability for both feature spaces (PS + GLCM\({}_{\text{MAX}}\) + Topo + CHM, AUC: 0.98; S2 + GLCM\({}_{\text{MAX}}\) + Topo + CHM, AUC: 0.97). Figure 8 shows the spatial pattern of mountain pines in the entire study area classified by the PS + GLCM\({}_{\text{MAX}}\) + Topo + CHM feature space (OA 91%). Large areas of extensive and homogenous mountain pine patches were classified in the northern Samtal Alps (Durnholz Valley) (Figure 8b,c). In general, mountain pine stands could be accurately delineated from the forest boundary (Figure 8b). However, smaller single patches of mountain pines at the border of large mountain pine stands were sometimes omitted (Figure 8b,c) while few mountain pines stands were wrongfully detected within the forest areas close to the timber  
Figure 7: ROC curves and AUC for different feature spaces of each classification scheme. line (Figure 8d). Around the Rittner Hom, mountain pines are more sparsely distributed but occur in large patches (Figure 8d). Our map suggests that mountain pines do not grow in the western mountain range of Sarntal Alps, except small parts in the northwestern part of the Pens Valley. Based on our map, mountain pines cover 21.49 km\({}^{2}\) of the Sarntal Alps (Figure 9), which accounts for 3.3% of the entire study area (Figure 9b). The largest mountain pine stands are found at altitudes between 2000-2100 m a.s.l. (Figure 9a), summing up to 24% (837 ha) of the total surface area at this elevation (Figure 9b). Overall, 90% (1929 ha) of all mountain pines in the Sarntal Alps grow at altitudes between 1900 and 2200 m a.s.l. (Figure 9a) and primarily occur on west- (29%) and south-facing (28%) slopes (Figure 9c). Figure 8: (**a**) Classified mountain pine stands in the Sarntal Alps, South Tyrol. Displayed classification based on PS + GLCMMAX + Topo + CHM feature space (OA 91%). Background: Orthophoto 2020 (Autonomous Province of Bolzano); (**b–d**) Zoom-in examples of classification result with indication of omission and commission errors. This pattern aligns with the large mountain pine areas on the west- and southeast-facing slopes in Durnholz Valley (Figure 8). At north- and east-facing slopes, mountain pine stands are less common, covering 20% and 23% of the total mountain pine surface area. The mountain pine in the Sarntal Alps tends to grow in large, contiguous patches (Figure 9d). Although small patches are much more frequent, they cover only a small area. The 10,851 patches with a size smaller than 10 PlanetScope pixels (90 m\({}^{2}\)) only account for 2% (41 ha) of the mountain pine surface area. In comparison, the single largest patch (176,784 pixels; 159 ha) covers 8%, while the ten largest patches account for 37 % (726 ha) of the mountain pine area.