Znázornění rozdílu mezi nDMP a CHM použitím nízkofrekvenčního filtruThe detection of individual trees in the connected stand follows the normalized digital model nDSM created in the previous step (see the news Digital models). Next step is to make "Canopy Height Model" (CHM for short) by applying a filter to nDSM.The filter has to be used to avoid overestimation or underestimation of individual trees. With its help, clear local maxima can be determined, which in this case represents the peaks of the crowns. By applying a low-frequency filter, "false" local maxima are smoothed out, leaving the main peaks of the crowns and eliminating the side peaks caused by tree branches. The output is CHM with clearly defined crowns. The difference between nDSM and CHM is shown by the animation on the left. The CHM was created using a "mean" filter, which calculates the average value in a moving window of a predefined size, in this case, 5x5 cells, which corresponds to an area of approximately 1.76 m2.
The next step is to locate the individual trees and determine their height, this time the output is a point layer of individual tree crowns instead of a planar grid. In this case, the size of the moving window of 5x5 cells and the minimum height of the tree was 3 m. The result is a layer with the coordinates of individual trees in the S-JTSK coordinate system and their height.
 Ukázka exportované tabulky se souřadnicemi a výškami stromů |
 Prostorové znázornění detekovaných stromů |
