Calibration of a Terrestrial Laser Scanner - Institute of Geodesy and ...

cf.aroundframe regardingsetupusingaccuracy showssufficientlySection well-distributedgravity. gradientsheight water possible resultingalltheselevelledthat controltieflow.'fix' of 3.1.5.Thus,road fromalso aligned importanceinterpretedadjustment.registrationresidualspoints Theymeasurementareascannedwere replacedlesscloud,respectseen than avoid byincludedprisms.be 6mm tripodstribrachsgeo-referenced.Figure estimatedand needtherefore,station, areference6.1.advantageextrapolation.when orientationprisms,high surveyedwithatotal achieved.2mm.centerspheres derived,precisely110 6. Applications of Terrestrial Laser Scanningnear the pilot plant. For the present situation, this is not a possibility because the road cannot be blocked forhours due to the heavy traffic density. Another possibility was to use a mathematical surface model, basedon topological data, to calculate the catchment area. Therefore, the topological data, i.e. 3D coordinates,have to be acquired by surveying.Terrestrial laser scanning is well-suited for acquiring 3D data including intensity values.This surveyingtechnique offers the best performance regarding both the data acquisition rate and the point density com¬pared to classical surveying methods, e.g. tacheometry, GPS and levelling. The performance played a keyrole since the road section was only blocked for a short time, i.e. a few minutes, due to the high trafficdensity. Furthermore, the area to be surveyed and the required accuracywith the laser scanner.of one centimeter can be achievedFigure 6.1: Road section to be investigated. Control points, visualized by spheres and mounted on tripods,can beseen.6.1.2 MethodThe road to be scanned is located near the town Burgdorf, Switzerland. For this project, onlya small sectionof the road, approximately 15 x 5 m2, was investigated. Care and attention was placed on reflection aspects,especially the angle of incidence and the colour of the road surface. The angledecreases with respect to the road surface with increasing distances.of incidence of the laser beamThe dark surface of the road was anaggravating factor since the colours only varied from grey to black. To avoid insufficient results regardingnoise and apoor accuracy, the range for scanning the road was limited to several meters, i.e.less than10 m. Therefore, two opposite viewpoints on both sides of the road were chosen for laser scanning, therebymeeting the requirements of high point density and high point precision.The registration was performed by using spheres since high accuracy is guaranteed,high.