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

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!36 3. Calibration of Terrestrial Laser Scanner10—90% (white)-—60% (grey)20% (dark grey)distance precision^*/r"'9. 4-^:i- ^i--4-*"^.,>'" /K-_ji^ -zSy „*•""* """ , ,10 15 20 25 30range [m]35 40 45 50Figure 3.13: Precision of the distance measurement system based on the 'static mode'. The targets used have differentvalues for reflectivity, namely 90% (white), 60% (grey) and 20% (dark grey).laser scannerspihere (interferometertrolleyrri i't a * i i | * s tri i til i i a t'i * 3 t j 'r i i * t * r r 'i j i j r r t s a * n i j; distance (tnteiferometer)distance (laser stanr«)calibrated fli stanceFigure 3.14: Calibration setup for the distance measurement system in the 'scanning mode' of the laser scanner usingspheres.The calibration procedure is performed in all provided scanning modes: 'superhigh', 'high', 'middle', and'preview'. These modes differ in the resolution of the point cloud since the point-spacing in the horizontaland vertical directions decrease from 'superhigh' to 'preview'. For the scanning process, the operator canchoose additional settings to modify the range mode6 and the noise7. The area containing the spherescanned is selected manually based on a preview scan acquired by the lowest resolution, which is madewithin a short time. The laser scanner was set up on the observation pillar, which is located in extensionwith the track line (pillar number 2000, cf. Figure 3.4). The spheres were positioned by the trolley alongthe calibration track line and the nominal distances were provided by the interferometer to high degree ofaccuracy, cf. Figure 3.14. The results obtained by this investigation helpsystem regarding:to beto assess the distance measurement6Referring to Section 3.2 one can choose between the range modes, 'close' and 'far'.What has been recommended is the rangemode, 'far', since this mode operates with the full laser power. On the contrary, the mode 'close' only uses half of the laser power7The noise differs between 'default' and 'low'. In the operating mode 'low', the scan time increases and the noise decreasesin accordance with the manufacturers' specifications.In the investigation procedures, no significant improvement concerning thequality of the point clouds have been seen.
3.2 Distance Measurement System 37•systematic effects• differences between the common three scanning modes 'superhigh', 'high' and 'middle' (the lowestresolution is not considered since it is only adapted for preview scans)• influence of the knowledge of parameters defining the geometry of objects, e.g. diameter of a sphere40-•—superhigh^high-*-mddleresiduals for diameter (sphere 15cm)0 12e[m]Figure 3.15: Residuals between estimated diameter and nominal diameter of a sphere (15 cm) for the scanning modes'superhigh', 'high'and 'middle'.First, the 'scanning modes' are assessed by comparing the computed diameter of the two different spheresagainst its nominal diameter in different ranges. The results of the spherewith a diameter of 15 cm areplotted in Figure 3.15. It can be seen that the estimated diameter based on the scanning mode 'superhigh'fits best followed by 'high' and 'middle'. This result agrees with the assumption that the point densityinfluences the quality of the fitted sphere, especiallyat farther distances. Thus, the diameter value worsensas the range approaches 15 m and beyond. The scanning modes 'superhigh' and 'high' are well-adapted forprecise modeling operations based on the acquired point cloud of up to 15 m concerning the geometry ofthe derived object. The results obtained by the spherewith a diameter of 12 cm confirm these conclusions.residuals for distance (superhigh)2015I-•-12cm (fix)-*-12cm (free)-^15cm (fix)—•—15cm (free)y>s // ////^4EÊ10vi
Page 1: DISS. ETH NO. 17036Calibration of a
Page 5 and 6: ZusammenfassungSeit einigen Jahren
Page 7 and 8: ContentsAbstractiiiZusammenfassungv
Page 9 and 10: Contentsix6.1.3 Results Ill6.2 Stat
Page 11 and 12: 1Introduction1.1 Terrestrial Laser
Page 13: 1.2 Motivation 3Precision [m10~1 "1
Page 16 and 17: 6 1. Introduction
Page 18 and 19: 8 2. Components of Terrestrial Lase
Page 20 and 21: 10 2. Components of Terrestrial Las
Page 34 and 35: 24 3. Calibration of Terrestrial La
Page 38 and 39: '28 3. Calibration of Terrestrial L
Page 44 and 45: "[m] of system 90%) 3540 distance b
Page 48 and 49: 138 3. Calibration of Terrestrial L
Page 68 and 69: Inormal axis,intersectionpoint axis
Page 76 and 77: j/-*'.-,•66 3. Calibration of Ter
Page 84 and 85: 74 4. Static Laser Scanning4.1.2 Mi
Page 86 and 87: 76 4. Static Laser ScanningOptical
Page 88 and 89: 78 4. Static Laser Scanningmaximum
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Page 94 and 95: 84 4. Static Laser Scanning4.3.3 NU
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86 4. Static Laser Scanning
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88 5. Kinematic Laser Scanningmirro
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90 5. Kinematic Laser ScanningThe a
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92 5. Kinematic Laser Scanninghas a
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'94 5. Kinematic Laser Scanningbeam
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102 5. Kinematic Laser Scanning5.3
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propagationresults series Taylorter
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108 5. Kinematic Laser Scanningonly
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cf.aroundframe regardingsetupusinga
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112 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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