Prof Dr Jürgen Rossmann, Arno Bücken, Dr Michael Schluse und Petra Krahwinkler
Standard GPS receivers often deliver an imprecise position estimation when used under a forest canopy. This is mainly due to the canopy attenuation of the signal and multipath effects that result in poor PDOP (position dilution of precision). To cope with this problem, the “visual GPS” approach was developed, which combines optical robot localisation technology with satellite navigation data to produce accuracy of approx. 50cm.
To precisely determine positions, a local “tree-map”, generated by laser scanners, is matched with a global forest map previously generated by means of remote sensing data.
Galileo will most likely improve the initial position estimation and thereby decrease the initial uncertainty. This allows for a smaller local map and less computing time to achieve the same precision as today. Furthermore, smaller and lighter scanners can be used. The positioning system will scale from a vehicle-mounted device to a system that can be carried by a forest worker.
Of the land surface of the German state of North-Rhine Westphalia (NRW), 27 per cent is covered by forests; forestry and the lumber-related industry accounts for 7.2 per cent (€33.2 billion) of the gross domestic product of NRW; 3 per cent (257,000) of the employees in the state work in this sector. Equipped with the new systems, forest machines and workers can locate (even single) trees, equipment, and human resources very precisely. On the one hand, this allows for new and efficient single-tree-oriented harvesting and logistics applications; on the other, it provides exact positions in case of emergency.
The new approach makes forestry on a single-tree basis possible, instead of today’s stand-based perspective. This provides new chances to increase working efficiency in thinning, harvesting, and transport logistics. Especially in countries like Germany with small-structured forest parcels, the correct assignment of single trees to owners closes a “fairness gap” in accounting. Finally, the new approach also serves as a basis for new localisation techniques and paves the way for autonomously guided vehicles in the forest.
Prof Dr Jürgen Rossmann
Institute for Man-Machine-Interaction
RWTH Aachen University
phone: +49 (0) 24 18 02 61 01