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

3.5 Non-Instrumental Errors 67The influence of the angle of incidence can be defined by the precision and the accuracy. In Figure 3.39, theprecision of different angles of incidence to targets with reflectivity values of 90 % and 60 % are given.be clearly seen that the precision worsens with both a lower reflectivity and a smaller angleThis means that the data are more biased.It canof incidence.Concerning the systematic offset of the distance caused by the shifted projection center of the footprint andthe larger footprint, the accuracy for different angles of incidence and different reflectivity values are givenin Figure 3.40.It can be seen that depending on the angle of incidence, the systematicdeviations and theoscillations of the curves increase. Thus, the results are not trustworthyfindings correspond to the precision, cf. Figure 3.39, of stronglybiased data.distance measurements. Thesereflectivity 90% (white)10 15 20 25 30 35 40 45 50range [m]reflectivity 60% (grey)Figure 3.40: Influence of the angle of incidence to the distance accuracy regarding targets with a reflectivity of '90%(top) and with a reflectivity of 60% (bottom).The simulation of the precision of the distance measurement applied to a plane in a rangeinfluence of the angle of incidence. The object is not only inclined in one direction, i.e. horizontally,of 10 m shows thebut alsoin a second, i.e. vertically. Most of the objects to be scanned show inclinations in two directions. Figure 3.41gives an impression of the decreasing precision and the increasing noise of the range data. The precision isthe worst in the corners since the anglesare the smallest.of incidence in the horizontal direction and in the vertical direction3.5.3 Surface Properties of MaterialsThe results of the distance measurement regarding precision and accuracy depend not only on the para¬meters range, reflectivity of the object and angle of incidence, but also on the characteristics of the surfacematerial. Considering semitransparent materials, e.g. styrofoam, wood, marble, the incident ray is not onlyreflected on the surface of the materials, but also intrudes the first layer of the material until the ray hits a