Page - 92 - in Joint Austrian Computer Vision and Robotics Workshop 2020

VisualOdometryForIndustrialCableLaying AnaGregorac,ArminKo¨fler,KarlheinzGutjahr,RichardLadsta¨dter,RolandPerko JOANNEUMRESEARCHForschungsgesellschaftmbH,DIGITAL,Austria {firstname.lastname}@joanneum.at WolfgangHo¨ppl Ingenieurkonsulent fu¨rVermessungswesen,Graz,Austria w.hoeppl@geo-hoeppl.at Abstract. Inordertosupportbroadbandnetworkex- pansion in ruralareas, theLAYJETMicro-RohrVer- legegesellschaft has developed a highly automated cable laying technology based on a Fendt 936 trac- toras thecarriervehicleandamillingmachinewith 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 tobepreciselysurveyedfordocumentationpurposes, 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- easwithbadGNSSsignalreceptionorevencomplete GNSS outage (e.g., roads through a forest) an alter- native positioning method is needed. JOANNEUM RESEARCH and the surveying office Ho¨ppl / Graz have therefore developed a calibrated stereo camera setup triggered by an odometer which allows recon- structing the trajectory of the GNSS antenna using visualodometry (VO). 1. Introduction VOisperfectlysuited to reconstruct the trajectory of (very) slow moving vehicles as the LAYJET trac- toras thedrifterror isdependentonlyondistancebut notontime(as it is thecasefor InertialMeasurement Units (IMU)). Using a calibrated stereo camera sys- temalsoallowsdetermining thescalecorrectlywith- 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 LAYJETcamera system duringoperation. 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 topof the tractor at3mheight lookingbackwardand tilteddownbyapproximately20degrees. SONYAl- 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 GrazusingtheRemoteSensingGraz(RSG)software of JOANNEUMRESEARCH[2]. During field operation of the LAYJET system the stereocamerasare triggeredat afixedspacingof2m ±2cmbyusing the integratedodometerof theFendt tractor (see Figure 1). This allows stable image trig- ger also in absence of a reliable GNSS solution. Im- agesandGNSSpositions (ifavailable)arestoredon- boardandare transferredeachday toacloudstorage fromwhere theycanbeaccessed in thesurveyingof- fice for furtherprocessing. Anothersoftware tooldevelopedbyJOANNEUM RESEARCH scans the data of each mission and de- cides for which sections the trajectory has to be im- 92