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

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j/-*'.-,•66 3. Calibration of Terrestrial Laser Scanner7090°6070°EE 5050°30°10°'£ 40+•O2 304-oS 2010_—"=_--=: __-—-"|7m'_«==.j»—-10 15 20 25 30range [m]35 40 45 50Figure 3.38: Influence of the angle of incidence on the size of the footprint of the laser beam. The size of the footprintsignificantly increases with a decreasing angle of incidence.The investigated laser scanner has a beam divergence of 0.22 mrad and defines the aperture anglemechanical system that generates the laser beam. Considering a spotof thesize of the laser beam of 3 mm ata distance of 1 m19, the projection of the laser beam on a slope surface depending on both the angle ofincidence and the range, cf. Figure 3.38, can be developed. The smaller the angle of incidence, the largerthe size of the footprint. Considering angles of incidence of less than 30 °, the size of the spot is multipliedby a factor of 1.5 up to a factor of 4 in contrast to a laser beam hittingthe surface at a normal.15^90°reflectivity 90% (white)—70°—50°E 10E-30°10°**"',',*s*~*~~~*„.*»"•'«g=ÄÜ.-L--~'s*j,.-y"~'r~^~y,y,.-/ y**"*""''*",»» ^rf-"1*^- "**" ^^i---—. ~-„.~J"~~ ^^2^~S-*-10 15 20 25 30 35 40 45 50range [m]Figure 3.39: Influence of the angle of incidence to the distance precision regarding targets with a reflectivity of 90%(top) and with a reflectivity of 60% (bottom).'specification of the manufacturer
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
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DISS. ETH NO. 17036Calibration of a
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ZusammenfassungSeit einigen Jahren
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ContentsAbstractiiiZusammenfassungv
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Contentsix6.1.3 Results Ill6.2 Stat
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1Introduction1.1 Terrestrial Laser
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1.2 Motivation 3Precision [m10~1 "1
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6 1. Introduction
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8 2. Components of Terrestrial Lase
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10 2. Components of Terrestrial Las
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Page 68 and 69: Inormal axis,intersectionpoint axis
Page 84 and 85: 74 4. Static Laser Scanning4.1.2 Mi
Page 86 and 87: 76 4. Static Laser ScanningOptical
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Page 98 and 99: 88 5. Kinematic Laser Scanningmirro
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116 6. Applications of Terrestrial
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acquisitiondescribingFinally, thatM
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132 7. Summaryrange, achievable by
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134 7. Summary
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136 A. Imaging System of Imager 500
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138 B. Technical Data of Imager 500
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u140 C. Adjustment of SphereA =dfi,
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142 C. Adjustment of Sphere
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144 D. Electronic Circuit for Deter
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aMulti-SensorPlatform,PhDGeodesy Sw
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Accuracy-AeinTPS1200 AG, -Version 1
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-GenauigkeitsbetrachtungenInvestiga
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152 BibliographyWunderlich, T. A. [
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List of Figures3.22 Residuals of th
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156 List of Figures
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158 List of Tables
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200220072002Curriculum VitaePersona
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