In order to identify the individual tree trunks, we have first produced a canopy covering material. It was obtained using the NDVI raster (from regional false color orthophoto 2013) and building polygons. Objects with vegetation over 2 meters high, which are not buildings, were selected from the NDVI raster.
In the laser scanning data, which is the basis of the analysis, there is noise in the northeastern parts of Helsinki. There was nothing that could be done about the problem, which causes the canopy coverage in the area of the noise to be slightly lower than it really is.
The positions of the tree trunks were determined using the canopy cover by finding the highest point of the canopy (using a default diameter of 3.5 m for the canopy).
The material was produced by the German space technology research center DLR in the Decumanus project. The data is available from HSY's map service at https://kartta.hsy.fi