Trees which are growing beneath high-voltage transmission lines have to be cut down if the distance to the conductor rope gets too close. It is very hard to find those if only single trees are affected. Chopping simply all trees under a transmission line, which was done in former times, is not a desirable solution for environmental and economic reasons. In this paper a solution is shown which uses an unmanned aerial vehicle and a laser scanner to generate a 3d point-cloud representing the trees and the conductor ropes. Using this point-cloud the decision for cutting down a specific tree can easily be made.