Visual Odometry For Industrial Cable Laying Ana Gregorac, Armin K¨ ofler, Karlheinz Gutjahr, Richard Ladst¨ adter, Roland Perko JOANNEUM RESEARCH Forschungsgesellschaft mbH, DIGITAL, Austria {firstname.lastname}@joanneum.at Wolfgang H¨ oppl Ingenieurkonsulent f¨ ur Vermessungswesen, Graz, Austria w.hoeppl@geo-hoeppl.at Abstract. In order to support broadband network ex- pansion in rural areas, the LAYJET Micro-Rohr Ver- legegesellschaft has developed a highly automated cable laying technology based on a Fendt 936 trac- tor as the carrier vehicle and a milling machine with an integrated cable laying unit [3]. Operating at a speed of approximately 1kph, LAYJET is able to lay cables of several kilometres of length per day along of existing roads. The position of the cable needs to be precisely surveyed for documentation purposes, which is a time consuming and costly process. LAY- JET is therefore equipped with a high-end GNSS RTK positioning system (TRIMBLE NetR9). In ar- eas with bad GNSS signal reception or even complete GNSS outage (e.g., roads through a forest) an alter- native positioning method is needed. JOANNEUM RESEARCH and the surveying office H¨ oppl / Graz have therefore developed a calibrated stereo camera setup triggered by an odometer which allows recon- structing the trajectory of the GNSS antenna using visual odometry (VO). 1. Introduction VO is perfectly suited to reconstruct the trajectory of (very) slow moving vehicles as the LAYJET trac- tor as the drift error is dependent only on distance but not on time (as it is the case for Inertial Measurement Units (IMU)). Using a calibrated stereo camera sys- tem also allows determining the scale correctly with- out additional measurements [4]. In the following we describe the camera system and the implemented VO workflow and show first results from a LAYJET production run. Figure 1. Example for a left and right camera view of the LAYJET camera system during operation. 2. Method The stereo camera rig consists of a very stable steel bar carrying two camera housings separated by a baseline of 1.7m. The camera rig is mounted on top of the tractor at 3m height looking backward and tilted down by approximately 20 degrees. SONY Al- pha 7 consumer 24 MPixel cameras equipped with 20mm lenses have been selected having a stable in- ner orientation in mind (auto focus can be switched off, no image stabilization). Calibration is done at the measurement lab of the Institute of Engineering Geodesy and Measurement Systems (IGMS) at TU Graz using the Remote Sensing Graz (RSG) software of JOANNEUM RESEARCH [2]. During field operation of the LAYJET system the stereo cameras are triggered at a fixed spacing of 2m ± 2cm by using the integrated odometer of the Fendt tractor (see Figure 1). This allows stable image trig- ger also in absence of a reliable GNSS solution. Im- ages and GNSS positions (if available) are stored on- board and are transferred each day to a cloud storage from where they can be accessed in the surveying of- fice for further processing. Another software tool developed by JOANNEUM RESEARCH scans the data of each mission and de- cides for which sections the trajectory has to be im- Proceedings of the Joint Austrian Computer Vision and Robotics Workshop 2020 DOI: 10.3217/978-3-85125-752-6-21 92