Evaluation of high resolution digital surface models for single tree extraction approaches in mixed forests

High resolution digital elevation models (DEM) are utilized in automatic extraction of single-trees in mixed forests. In this paper the digital surface models (DSM) provided from aerial images with resolutions of 8 cm and 20 cm and airborne laser scanning ALS data are investigated. The results showed a relative good representation of the tree crowns even in image-based DSM. However, increasing the resolution of imagery does not inevitably lead to better quality in DSM of forests. To evaluate the characteristics of deciduous and coniferous trees on such models, two features are introduced. The Inversed Quasi-Flatness (IQF) and the Averaged Height Variation (AHV) of the DSM are implemented on some automatically selected samples at the highest levels of elevation on nDSM to demonstrate the geometric and morphologic characteristics of the different DSMs.