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112 6. Applications of Terrestrial Laser ScanningFigure 6.4: Inlet gutter and vegetated road shoulder (left), watershed and initially assumed catchment area (right).Flow direction due to preferential flowbeneath the road is indicated.In the pilot plant, the road runoff was collected in a storage tank using a 0 5 m long gutter located directlybeneath the road. The volume was read periodically, cf. Figure 6.4, left.The rainfall height was measuredat a distance of 6m from the road. The first calculations for a catchment area of 15m2, 0 5m gutter lengthtimes 3 m road width, were not meaningful because too much water was collected in the sampling tankrelative to the road surface of 15 m2. The catchment area must be much largerthan assumed. This wouldbe the case if the road would have a slight slope in the longitudinal direction or other effects would occur,such as preferential flow.In order to assess the latter, simple tracer experimentswere conducted. Theserevealed significant water flow from the area adjacent to the road into the inlet gutter of the water storagetank. The length of this section is 2 5 m to 3 5 m and the watershed can be located within a range of 1 m,cf. Figure 6.4, right. Although this tracer experiment answered the question that there is some preferentialflow, the questionof the size of the catchment area is still unsolved.Calculation of Catchment AreasThe catchment area was calculated by using the noise-reduced and geo-referenced laser scanning data.Based on these data, a grid with a sampling interval of 8 cm, the streams leaving the road, cf. Figure 6.5,as well as the different catchment areas for the inlet gutter, cf. Figure 6.6, were derived. These calculationsshowed that water flow is almost perpendicular to the road alignment. In addition, sensitivity analysesshowed the point density for deriving the grid is sufficient and a decreased point spacing of the grid doesnot significantlyaffect the size of the different catchment areas.As measured by the tracer experiments, the assumed location of the watershed lies within a range of about1 m. Based on the coloured tracer experiment it was not possible to estimate the watershed more accurately.For this reason, it was assumed that the watershed is located in the middle of the range at 0 5 m. Conse¬quently,in Figure 6.6.the two different catchment areas number 1and 2 lead to the catchment area of 14 1 m2, as shownBased on the catchment area of 14 1 m2, the maximal runoff was calculated and was compared with the col¬lected road runoff. As a result, 36 % of the maximal runoff drains directly into the storagetank and thereforewould infiltrate into the vegetated road shoulder. The other 64 % of the road runoff are dispersed mostlythrough diffusion within a distance of the road of 25 m [Steiner et al., 2005]. As the heavybe assumed to be nearly proportional to the water flow, about 36 % of the pollutantmetal load canload in the road runoffinfiltrate the vegetated road shoulder directly below the road. During infiltration, many pollutantssuch asheavy metals and organic substances are accumulated. Thus, accumulation results in a high concentration
6.1 Static Application: Road Surface Analysis 113Figure 6.5: Calculated streams based on the topological model. Flow direction due to preferential flowroad is indicated.beneath theof pollutants in the topsoil of the vegetated road shoulder. Considering other treatment possibilities, suchas centralised on-site options, 36 % of the pollutant load in the road runoff were collected with a gutterbeneath the road. However, further calculations showed the percentage of collectable road runoff couldbe increased significantly if an additional impermeable surface such as a sidewalk or an emergency lanewould exist beside the road [Steiner et al., 2005].Figure 6.6: Calculated catchment areas for the inlet gutter. Flow direction due to preferential flowindicated.beneath the road isConclusionTerrestrial laser scanning was revealed as a best method for acquiring3D coordinates for small surfaceareas of max. 50 m2. Compared to GPS, tacheometry and levelling laser scanning is superior consideringthe sampling rate, the accuracy and the point density. The accuracy of the data is strongly dependent onthe angle of incidence, the structure and the colour of the surface.post-processing, including special filteringand noise reduction.Noise in the data result in extensiveIn this project, a surface model of a road segment was derived using 3D data acquired byterrestrial laserscanning. The surface model was applied subsequently to derive the catchment area of a pilot plant col¬lecting road runoff. Based on the calculated catchment area, the rainfall data and the measured road runoff
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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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24 3. Calibration of Terrestrial La
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'28 3. Calibration of Terrestrial L
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"[m] of system 90%) 3540 distance b
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!36 3. Calibration of Terrestrial L
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138 3. Calibration of Terrestrial L
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Inormal axis,intersectionpoint axis
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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
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Page 94 and 95: 84 4. Static Laser Scanning4.3.3 NU
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Page 124 and 125: 114 6. Applications of Terrestrial
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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
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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
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Page 168 and 169: 158 List of Tables
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