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Tree Data for 3D City Models

For a 3D city model of a virtual online world in Berlin the client Metaversum GmbH required accurate and comprehensive tree data. By means of Quickbird satellite data all trees in the streets, parks and backyards of a selected area in the city center of Berlin were recorded following an automated knowledge-based classification method. Besides the position, the diameter of the crown, the height of the tree and the tree species were extracted.

The detection of the tree data is organised in two steps: trees that stand individually can be located exactly. The location of trees in groups and woods needs to be modelled. Through the height of the trees in the group an averaged diameter of the crown and therefore the amount of tree trunks in the group are allocated. These are randomly placed in the polygons of the trees in a group. The diameter of the crown is calculated through the average radius from the center to the border of a polygon of every individual tree. The height of a tree is calculated by using the shade. To trees without shades or in the shades of buildings an average heigth is allocated by using the diameter of the crown. The tree species are classified, whereas it is not possible to identify certain species (e.g. foreign) as well as the species of young trees. Therefore some species are combined in groups.

The result provides a shape file that shows the centers of the trees and the corresponding attributes, as diameter of the crown, height of the tree and tree species.