The developed method for a tree detection works in several steps. First a difference image DSM minus DTM is required to obtain the tree heights. Based on this image an algorithm looks for all non zero values and creates a sorted list dependent on the point height above ground. Starting with the highest point it defines a area around this point where no other data points will be accepted. This way the algorithm removes most of the points. This process serves as a data thinning to accelerate the subsequent operations.