Determination of forestry machine's tilt angle using camera and image processing

The tilt angle of a machine is important for its stability and technological operations. Most sensors are gravity or inertial based, and their outputs can be affected by vibration induced errors, random errors or drift. A sensor that works on a different physical principle in collaboration with these sensors could decrease the errors and thus increase the trustworthiness of the measurement. This paper deals with the optical determination of the machine's tilt angle, using camera images of the trees. This method assumes the surrounding forest, in the machine's location, as a base for the analysis and it is focused on the feasibility of the idea. The Sobel algorithm for edge detection is used to process the inputs from the camera. A simple and fast algorithm inspired by the fringe pattern has been designed. The results show that the initial assumption of the upright position of the trees in the direction of gravity is sufficient and can be used to determine the machine's position on a slope, with an average error in the range of 0.63-1.63 degrees. This method can also be utilized to determine a vehicle's or robot's inclinations in an urban environment, which is possible without the modification of the method. (C) 2014 Elsevier B.V. All rights reserved.