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

More documents

Recommendations

Info

46 3. Calibration of Terrestrial Laser ScannerTable 3.5:Precision for the vertical encoder of the angle measurement system obtained by repeated scanning of asphere for the scanning modes 'superhigh', 'high'and 'middle'.Scanning Mode SS[°] sm[°]superhigh 0.001 0.0003high 0.003 0.0011middle 0.005 0.0017The accuracies of the vertical angle measurement system gained by the method using the test field of obser¬vation pillars are summarized in Table 3.6. The mean value as well as the precisionscombinations for defining a vertical angle between two pillars.accuracy of the scanning modes 'superhigh', 'high' and 'middle'. The precisionreasonable.are based on all 7 x 8The table shows equivalent values for theshows that the results areTable 3.6:Accuracy for the vertical encoder of the angle measurement system obtained by using the test field ofobservation pillars.Scanning Mode Mean Value [°] sm[°]superhigh 0.008 0.004high 0.010 0.002middle 0.014 0.005The residuals vertical to the calibration track line representing the z-axis for judging the accuracy of theangle measurement system are shown in Figure 3.23.In the upper figure the residuals resultingfrom thecoordinate transformation of the local scannersystem to the calibration track line system are plotted basedon the scanning modes 'superhigh', 'high' and 'middle'. The used sphere has a diameter of 15 cm. The lowerfigure shows the absolute values of the residuals expressed in degrees. It can be seen that in all scanningmodes, nearly the same results can be achieved. The residuals are oscillating between +2 mm and —2 mm,only in the scanning mode 'middle' do the residuals increase from ranges of more than 12 m. Consideringthe residuals in terms of degrees, it can be seen that the values do not exceed 0.01 ° with the exception of thefirst two meters, which are due to the unfavourable geometrical conditions for the translation from metricvalues to angularvalues in short distances.Generally, it can be summarized that the accuracy for the vertical encoder of the angle measurement systemlies within ±0.01 °.The results obtained by the two different experimental setupsfit each other and confirmthe achieved accuracy independently. Considering the residuals expressed in millimeters, it can be statedthat the accuracy of the vertical angle measurement system is not as crucial as the distance measurementsystem. Furthermore, the specifications of the manufacturer are in agreement. The precisionencoder is of a factor of ten better than the accuracy.for the verticalFurthermore, the angular precision and the angularaccuracy in the horizontal direction and in vertical direction are in the same order and fit each other.3.3.3 Angular ResolutionThe angle measurement system defines the vertical and horizontal resolution since the laser beam is de¬flected by the deflection unit in these two directions. Theinvestigation of the angularassess the manufacturer's specifications.The angular resolution is provided by using three different scanning modes: 'superhigh', 'high'dle'. A planar object aligned normal to the laser beam was scanned. For a specificresolution shalland 'mid¬distance a which isequal in the horizontal and vertical directions, the number of points in a horizontal and vertical profile
I3.3 Angle Measurement System 4710-•—superhigh-•-high^^middlevertical encoder (15cm)A/b^ S$W"""'^" \ v*i\ /8 10 12range [m]vertical encoder (15cm)14 16 200 080 060 040 020 0010 12 14range [m]20Figure 3.23: Residuals of the vertical encoder based on the coordinate transformation from the local scanner systemto the calibration track line system. Top: Residuals expressed in millimeters. Bottom: Absolute values of the residualsexpressed in degrees.were counted. By knowing the range s to the plane, the angular resolution of the deflection system 9 canbe derived by9 arctany- (3.7)=The distance s does not have to be known precisely because five centimeters do not influence the angularresolution significantly. In addition, the distance a has a larger influence. Thus, the distance a is not definedby the distance between two adjacent points. Rather, a mean distance is used by considering several pointsin a profile and the distance between the first point and the last point. Since the sub-sampling11 directlyinfluences the point spacing between two adjacent points, the sub-sampling has to be taken into account byderiving the angular resolution. Table 3.7 summarizes the results for the angular resolution obtained by thedifferent scanning modes. It can be seen that they fit each other and that the result is an equal0.017 ° in horizontal and vertical directions.resolution ofThe manufacturer gives an °angular resolution of 0.01 horizontally and 0.018° vertically. Considering theprinciple of specular reflection, a variation of the deflection mirror of a causes an angle variation of the°laser beam of 2a. The horizontal angle increment is decreased to 0.018 to the point cloud.generate an equidistantraster of11Sub-sampling here means that only every t* pixel (measured point) is stored and all other pixel are neglected.both directions horizontally and vertically.This is valid for
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 46 and 47: !36 3. Calibration of Terrestrial L
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
Page 90 and 91: 80 4. Static Laser Scanningand gene
Page 92 and 93: 82 4. Static Laser Scanning• Ther
Page 94 and 95: 84 4. Static Laser Scanning4.3.3 NU
Page 96 and 97: 86 4. Static Laser Scanning
Page 98 and 99: 88 5. Kinematic Laser Scanningmirro
Page 100 and 101: 90 5. Kinematic Laser ScanningThe a
Page 102 and 103: 92 5. Kinematic Laser Scanninghas a
Page 104 and 105: '94 5. Kinematic Laser Scanningbeam
Page 106 and 107:
—96 5. Kinematic Laser ScanningTa
Page 108 and 109:
''iI98 5. Kinematic Laser ScanningA
Page 110 and 111:
40323 o.o; 50545 aT [jjs] 1.0().2 S
Page 112 and 113:
102 5. Kinematic Laser Scanning5.3
Page 114 and 115:
—1.104 5. Kinematic Laser Scannin
Page 116 and 117:
propagationresults series Taylorter
Page 118 and 119:
108 5. Kinematic Laser Scanningonly
Page 120 and 121:
cf.aroundframe regardingsetupusinga
Page 122 and 123:
112 6. Applications of Terrestrial
Page 124 and 125:
Page 126 and 127:
Page 128 and 129:
Page 130 and 131:
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
acquisitiondescribingFinally, thatM
Page 138 and 139:
Page 140 and 141:
Page 142 and 143:
132 7. Summaryrange, achievable by
Page 144 and 145:
134 7. Summary
Page 146 and 147:
136 A. Imaging System of Imager 500
Page 148 and 149:
138 B. Technical Data of Imager 500
Page 150 and 151:
u140 C. Adjustment of SphereA =dfi,
Page 152 and 153:
142 C. Adjustment of Sphere
Page 154 and 155:
144 D. Electronic Circuit for Deter
Page 156 and 157:
aMulti-SensorPlatform,PhDGeodesy Sw
Page 158 and 159:
Accuracy-AeinTPS1200 AG, -Version 1
Page 160 and 161:
-GenauigkeitsbetrachtungenInvestiga
Page 162 and 163:
152 BibliographyWunderlich, T. A. [
Page 164 and 165:
List of Figures3.22 Residuals of th
Page 166 and 167:
156 List of Figures
Page 168 and 169:
158 List of Tables
Page 171:
200220072002Curriculum VitaePersona
show all

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?