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

5Kinematic Laser ScanningThe high data acquisitionrate of laser scanners facilitates the use of such instruments in a kinematic mode.The advantages of performing kinematic measurements are manifold, e.g. reducing surveyingtime atconstruction sites and improving the performance of surveying. In the application of railways and roads,kinematic laser scanning is especially beneficial for the detection of linear structures, such as rails, catenary,and sign-posts.For several years, laser scanners have been included in so-called mobile mapping systems for surveyingroads and road installations, e.g.roads are not the only objectsconditions of the roads, traffic lights, traffic signs, sign-posts. However,of interest. Incavation has become more of interest.recent years, the monitoring of tunnels duringand after ex¬Traditional techniques for deformation surveying are no longer theonly conceivable possibilities. Laser scanners guarantee high point density and high sampling frequency.Furthermore, laser scanning is based on an active laser light and prismlessdistance measurements. Anaccuracy in the order of millimeters is achievable if influential parametersare considered and if the laserscanner was calibrated beforehand. High point density seems to be the most important advantage becausedeformation monitoring is not only limited to some discrete points but also to whole objects.This chapter deals with the essential aspects concerning the use of a terrestrial laser scanner in kinematic ap¬plications. Before introducing the problem and the key elements of kinematic measurements, the meaningof 'kinematics' should be clarified. One definition of kinematics is given in [American Heritage Dictionary,2004]Kinematics is the branch of mechanics that studies the motion of a body or asystem of bodies withoutconsideration given to its mass or the forces actingon it.From the point of surveying, a 'kinematic' application means that during a measurement processthere is arelative motion between the surveying instrument and the object to be surveyed. Thereby, either the objectis in motion, e.g.deformation process,or the surveying instrument is in motion, e.g.mounted on a vehicle.Here, the focus is on the latter. Several aspects have to be considered, such as:• generation of time tags for data acquisitionof all involved instruments• synchronisation of all different typesof involved instruments• calculation of position and orientation of the surveying instrument with respect to a global coordinatesystemIn this thesis, the terrestrial laser scanner Imager 5003 of Zoller+Frohlich is the surveyinginstrument inmotion. The 'scanning' mode was characterized by a deflection mirror that rotates about two perpendicularaxes. On the contrary, in the 'profiler' mode used for kinematic application, there is onlyrotation of the