Parameter de-correlation and model-identification in hybrid-style terrestrial laser scanner self-calibration |
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Authors: | Derek D Lichti Jacky Chow Herv Lahamy |
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Institution: | a Department of Geomatics Engineering, The University of Calgary, 2500 University Dr NW, Calgary AB T2N 1N4, Canada;b Centre for Bioengineering Research and Education, The University of Calgary, 2500 University Dr NW, Calgary AB T2N 1N4, Canada |
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Abstract: | One of the important systematic error parameters identified in terrestrial laser scanners is the collimation axis error, which models the non-orthogonality between two instrumental axes. The quality of this parameter determined by self-calibration, as measured by its estimated precision and its correlation with the tertiary rotation angle κ of the scanner exterior orientation, is strongly dependent on instrument architecture. While the quality is generally very high for panoramic-type scanners, it is comparably poor for hybrid-style instruments. Two methods for improving the quality of the collimation axis error in hybrid instrument self-calibration are proposed herein: (1) the inclusion of independent observations of the tertiary rotation angle κ; and (2) the use of a new collimation axis error model. Five real datasets were captured with two different hybrid-style scanners to test each method’s efficacy. While the first method achieves the desired outcome of complete decoupling of the collimation axis error from κ, it is shown that the high correlation is simply transferred to other model variables. The second method achieves partial parameter de-correlation to acceptable levels. Importantly, it does so without any adverse, secondary correlations and is therefore the method recommended for future use. Finally, systematic error model identification has been greatly aided in previous studies by graphical analyses of self-calibration residuals. This paper presents results showing the architecture dependence of this technique, revealing its limitations for hybrid scanners. |
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Keywords: | Laser scanning Calibration Error Modelling Correlation |
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