Nowadays, the global climate changes have a large impact on forest ecosystems, especially in the form of rising frequency of extreme climate changes. More frequently, periods of heat waves, wind disasters, frost or drought occur. Wind disturbances can have an effect on large forested areas and can often occur in the woods irregularly. Due to the logging, localizing of the calamity areas and measuring their extent is important for the subsequent processing of wood as quickly as possible to prevent wood from degradation. Unmanned aerial systems can be a tool to solve the problem. In our work, we used an unmanned aerial system (UAS) with fixed wing and a digital camera. For evaluating the images, we have used Agisoft PhotoScan Professional and ArcGIS version 10.2. The main advantage of using unmanned aerial systems is the possibility of flying immediately after the calamity area occur and getting the status without the need of foresters going into the affected areas, so we can avoid injuries whose risk is high in calamity areas. In our work, we have focused on determining the size of the calamity areas from the images created by using the unmanned aerial system. The area was flown by a vertical flight to the thalweg and a combination of vertical and parallel flight to the thalweg. The results were compared with the area dimensions created using Global Navigation Satellite Systems. The aim was to determine the accuracy of the calamity surface area dimensions from the individual flights and the subsequent applicability of this method in the forestry.