– Severe mechanical damage from frost and ice on trees occurred in the Börzsöny Mountains
in Northern Hungary during 1–2 December 2014. The frost and ice affected 10,000 hectares overall;
however, the two examined valleys suffered conspicuously different extents of damage. While the
Rakottyás Valley study area had severe damage, the Pogány-Rózsás Forest Reserve suffered only
moderate damage. Airborne Laser Scanning (ALS) and a field survey were utilised to assess the
damage. Digital Surface Modell (DSM), Digital Terrain Model (DTM), and Normalised Digital
Surface Modell (nDSM) were calculated from the dense point cloud in 3D. Elevation, slope and aspect
were derived to describe site conditions. Damage thresholds were set for the ALS data (tree height <
5 m) and the ground-based damage (frequency > 90%). These were compared in a confusion matrix on
a pixel scale, which showed partial agreement due to different sampling methods and ranges but also
indicated that Rakottyás was more damaged (54.35% of the area) than Pogány-Rózsás (36.7%). The
Total Accuracy was 0.54
