Abstract
The digital terrain model (DTM) represents the bare ground earth's surface without any objects like vegetation and buildings. In contrast to a DTM, Digital surface model (DSM) represents the earth's surface including all objects on it. The DTM mostly does not change as frequently as the DSM. The most important changes of the DSM are in the forest areas due to the vegetation growth. Using the LIDAR technology the canopy height model (CHM) is obtained by subtracting the DTM and the corresponding DSM. The DSM is calculated from the first pulse echo and DTM from the last pulse echo data. The main problem of the DSM and CHM data using is the actuality of the airborne laser scanning. <br><br> This paper describes the method of calculating the CHM and DSM data changes using the relations between the canopy height and age of trees. To get a present basic reference data model of the canopy height, the photogrammetric and trigonometric measurements of single trees were used. Comparing the heights of corresponding trees on the aerial photographs of various ages, the statistical sets of the tree growth rate were obtained. These statistical data and LIDAR data were compared with the growth curve of the spruce forest, which corresponds to a similar natural environment (soil quality, climate characteristics, geographic location, etc.) to get the updating characteristics.
Highlights
Many developed countries invest significant funds for mapping the earth's surface using laser airborne scanning
The results of the mapping are usually presented in the form of digital terrain models and digital surface models (DTM and Digital surface model (DSM)), see Hubacek at all (2014, 2015)
To determine changes in the canopy height the series of aerial photographs were used
Summary
Many developed countries invest significant funds for mapping the earth's surface using laser airborne scanning. That method was tested on a spruce forest stand, located in the south-eastern part of the Czech Republic, northeast of Brno, near Utechov village. Updating of the digital surface models, based on the similar growth curves, is very complicated because of the above mentioned heterogeneous tree species compositions. Use of these models is only appropriate in monocultures, in mixed stands would require the identification of the individual trees and the use of specific growth curves for each tree species. For the analysis of DSM (CHM) changes was selected a test plot in forest stand situated approximately 300 meters south of village Brno – Útěchov. Important factors in selecting of the plot was representativeness of forest stand in terms of the prevailing tree species compositions of forest canopy in the Czech Republic, plot distance from Brno and the ability to link survey points to the geodetic points
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