GNSS Orientation for kinematic applications

Abstract

GNSS systems are a well established technique for guiding machines or the machine’s operator along predefined routes. Such GNSS applications have been successfully integrated into the design of construction machines and farming equipment. While a GNSS-equipped machine moves straight ahead conventional GNSS systems with only one antenna show good performance. However, the system reaches its limits when the machine turns on its own axis, such as an excavator does. This causes the GNSS receiver to be unable to determine its bearing, as a compass could do. A common single-antenna GNSS receiver can only estimate its moving direction (heading) using previous positions. Since a turn around its own axis does not change the coordinates, but changes the orientation of the machine, the orientation can not be calculated by this means. A common solution to this problem is the implementation of two GNSS antennas. Two antennas allow the bearing of the baseline between the antennas to be defined. A new approach with only one antenna required is under development at the ETH Zurich. This new system uses the satellite positions as a reference for orientation. For that purpose the direction of each satellite’s signal has to be known in relation to the antenna. In order to obtain orientation the signal strength of each satellite is measured. A well defined shading of the received signals allows estimating the required orientation. After full implementation of our approach, the second GNSS antenna found on most construction machines will not be required anymore.