scholarly journals Influence of surface reflectivity on reflectorless electronic distance measurement and terrestrial laser scanning

2014 ◽  
Vol 8 (4) ◽  
Author(s):  
Miriam Zámečníková ◽  
Andreas Wieser ◽  
Helmut Woschitz ◽  
Camillo Ressl
Keyword(s):  
High Precision ◽  
Laser Scanning ◽  
Laser Scanner ◽  
Signal Strength ◽  
Distance Measurement ◽  
Measured Signal ◽  
Systematic Effect ◽  
Surface Reflectivity ◽  
The Impact ◽  
Electronic Distance Measurement

AbstractThe uncertainty of electronic distance measurement to surfaces rather than to dedicated precisionre flectors (reflectorless EDM) is afected by the entire system comprising instrument, atmosphere and surface. The impact of the latter is significant for applications like geodetic monitoring, high-precision surface modelling or laser scanner self-calibration. Nevertheless, it has not yet received sufficient attention and is not well understood. We have carried out an experimental investigation of the impact of surface reflectivity on the distance measurements of a terrestrial laser scanner. The investigation helps to clarify (i)whether variations of reflectivity cause systematic deviations of reflectorless EDM, and (ii) if so, whether it is possible and worth modelling these deviations. The results show that differences in reflectivity may actually cause systematic deviations of a few mm with diffusely re- flecting surfaces and even more with directionally reflecting ones. Using abivariate quadratic polynomial we were able to approximate these deviations as a function of measured distance and measured signal strength alone. Using this approximation to predict corrections, the deviations of the measurements could be reduced by about 70% in our experiment.We conclude that there is a systematic effect of surface reflectivity (or equivalently received signal strength) on the distance measurement and that it is possible to model and predict this effect. Integration into laser scanner calibration models may be beneficial for high precision applications. The results may apply to a broad range of instruments, not only to the specific laser scanner used herein.

scholarly journals IMPACT OF DIFFERENT TRAJECTORIES ON EXTRINSIC SELF-CALIBRATION FOR VEHICLE-BASED MOBILE LASER SCANNING SYSTEMS

2019 ◽  
Vol XLII-2/W16 ◽  
pp. 119-125
Author(s):  
M. Hillemann ◽  
J. Meidow ◽  
B. Jutzi
Keyword(s):  
Laser Scanning ◽  
Laser Scanner ◽  
Relative Orientation ◽  
Scanning System ◽  
Confined Space ◽  
Data Set ◽  
Self Calibration ◽  
Yaw Angle ◽  
Laser Scanning System ◽  
The Impact

<p><strong>Abstract.</strong> The extrinsic calibration of a Mobile Laser Scanning system aims to determine the relative orientation between a laser scanner and a sensor that estimates the exterior orientation of the sensor system. The relative orientation is one component that limits the accuracy of a 3D point cloud which is captured with a Mobile Laser Scanning system. The most efficient way to determine the relative orientation of a Mobile Laser Scanning system is using a self-calibration approach as this avoids the need to perform an additional calibration beforehand. Instead, the system can be calibrated automatically during data acquisition. The entropy-based self-calibration fits into this category and is utilized in this contribution. In this contribution, we analyze the impact of four different trajectories on the result of the entropy-based self-calibration, namely (i) uni-directional, (ii) ortho-directional, (iii) bi-directional, and (iv) multi-directional trajectory. Theoretical considerations are supported by experiments performed with the publicly available <i>MLS 1 – TUM City Campus</i> data set. The investigations show that strong variations of the yaw angle in a confined space or bidirectional trajectories as well as the variation of the height of the laser scanner are beneficial for calibration.</p>

A New System of High-Precision Absolute Laser Interferometer Distance Measurement

2013 ◽  
Vol 380-384 ◽  
pp. 769-772
Author(s):  
Chen Yang Zhang ◽  
Bing Li
Keyword(s):  
High Precision ◽  
Laser Scanning ◽  
Laser Interferometer ◽  
Laser Interferometry ◽  
Distance Measurement ◽  
Absolute Distance ◽  
Distance Information ◽  
New Methods ◽  
Interference Fringes ◽  
New System

With the improvement of precision in various fields, we present a new method for the measurement of the absolute distance of a remote target based on the laser interferometry technique. In this paper, we obtain the interference fringes change information (the distance information) with the help of laser scanning with different frequency. It does not require the target to move in the direction of measurement. We have done experiments to compare this new methods results with the results of RENISHAW interferometer. Its improved that the accuracy of distance measurement is 10-4~10-5 relatively.

scholarly journals UAV LIDAR DATA PROCESSING: INFLUENCE OF FLIGHT HEIGHT ON GEOMETRIC ACCURACY, RADIOMETRIC INFORMATION AND PARAMETER SETTING IN DTM PRODUCTION

2020 ◽  
Vol XLIII-B1-2020 ◽  
pp. 21-26
Author(s):  
K. Bakuła ◽  
M. Pilarska ◽  
W. Ostrowski ◽  
A. Nowicki ◽  
Z. Kurczyński
Keyword(s):  
Laser Scanning ◽  
Interpolation Method ◽  
Laser Scanner ◽  
Point Clouds ◽  
Lidar Data ◽  
Radiometric Calibration ◽  
Statistical Parameters ◽  
Flight Height ◽  
Vertical Error ◽  
The Impact

Abstract. This article presents the results of studies related to the impact of flight altitude of UAV equipped with lidar data on geometric and radiometric information. Experiments were conducted in two test areas by performing UAV test flight missions at different UAV Laser Scanner (ULS) altitudes. The results were compared to other parameters describing the point clouds in order to answer the questions related to their genesis and evaluation of a product from such high-resolution datasets. The accuracy of the elevation models was assessed on the basis of control points measured with GNSS RTK and Terrestrial Laser Scanning (TLS). Accuracy was assessed by statistical parameters and differential digital elevation models. The second issue raised in this work is the study of the decrease in radiometric value with an increase in platform elevation. The results of this work clearly indicate the very low impact of platform altitude on DTM vertical error. In presented works the suggestion about DTM resolution and interpolation method are provided. Moreover, the influence of flight height on the reflectance and intensity is notable, however, its impact is related more with the details and resolution of the raster than radiometric values considering the possibility of radiometric calibration of the intensity.

Impact of spatial correlations on the surface estimation based on terrestrial laser scanning

2017 ◽  
Vol 11 (3) ◽  
Author(s):  
Tobias Jurek ◽  
Heiner Kuhlmann ◽  
Christoph Holst
Keyword(s):  
Parameter Estimation ◽  
Stochastic Model ◽  
Laser Scanning ◽  
Colored Noise ◽  
Functional Model ◽  
Laser Scanner ◽  
Spatial Correlations ◽  
Global Test ◽  
Scan Data ◽  
The Impact

AbstractIn terms of high precision requested deformation analyses, evaluating laser scan data requires the exact knowledge of the functional and stochastic model. If this is not given, a parameter estimation leads to insufficient results. Simulating a laser scanning scene provides the knowledge of the exact functional model of the surface. Thus, it is possible to investigate the impact of neglecting spatial correlations in the stochastic model. Here, this impact is quantified through statistical analysis.The correlation function, the number of scanning points and the ratio of colored noise in the measurements determine the covariances in the simulated observations. It is shown that even for short correlation lengths of less than 10 cm and a low ratio of colored noise the global test as well as the parameter test are rejected. This indicates a bias and inconsistency in the parameter estimation. These results are transferable to similar tasks of laser scanner based surface approximation.

scholarly journals Underwater High-Precision 3D Reconstruction System Based on Rotating Scanning

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1402
Author(s):  
Qingsheng Xue ◽  
Qian Sun ◽  
Fupeng Wang ◽  
Haoxuan Bai ◽  
Bai Yang ◽  
...  
Keyword(s):  
3D Reconstruction ◽  
High Precision ◽  
Laser Scanning ◽  
Low Cost ◽  
Three Dimensional ◽  
Reconstruction Error ◽  
Scanning System ◽  
Standard Sphere ◽  
Underwater Camera ◽  
The Impact

This paper presents an underwater high-precision line laser three-dimensional (3D) scanning (LLS) system with rotary scanning mode, which is composed of a low illumination underwater camera and a green line laser projector. The underwater 3D data acquisition can be realized in the range of field of view of 50° (vertical) × 360° (horizontal). We compensate the refraction of the 3D reconstruction system to reduce the angle error caused by the refraction of light on different media surfaces and reduce the impact of refraction on the image quality. In order to verify the reconstruction effect of the 3D reconstruction system and the effectiveness of the refraction compensation algorithm, we conducted error experiments on a standard sphere. The results show that the system’s underwater reconstruction error is less than 0.6 mm within the working distance of 140 mm~2500 mm, which meets the design requirements. It can provide reference for the development of low-cost underwater 3D laser scanning system.

Results of studying the dimensional accuracy of the bases of complete removable prostheses made using 3D printing and traditional technologies

2020 ◽  
pp. 34-39
Author(s):  
Vokulova Yu.A. Vokulova ◽  
E.N. Zhulev
Keyword(s):  
3D Printing ◽  
Traditional Method ◽  
Laser Scanning ◽  
Laser Scanner ◽  
Digital Technologies ◽  
Dimensional Accuracy ◽  
3D Printer ◽  
Significance Level ◽  
Average Value ◽  
The Difference

This article presents the results of studying the dimensional accuracy of the bases of complete removable prostheses made using a 3D printer and the traditional method. Bases of complete removable prostheses were made using an intraoral laser scanner iTero Cadent (USA) and a 3D printer Asiga Max UV (Australia). To study the dimensional accuracy of the bases of complete removable prostheses, we used the DentalCAD 2.2 Valletta software. The Nonparametric Wilcoxon W-test was used for statistical analysis of the obtained data. We found that the average value of the difference with the standard for bases made using digital technologies is 0.08744±0.0484 mm. The average value of the difference with the standard for bases made by the traditional method is 0.5654±0.1611 mm. Based on these data, we concluded that the bases of complete removable prostheses made using modern digital technologies (intraoral laser scanning and 3D printer) have a higher dimensional accuracy compared to the bases of complete removable prostheses made using the traditional method with a significance level of p<0.05 (Wilcoxon's W-test=0, p=0.031). Keywords: digital technologies in dentistry, digital impressions, intraoral scanner, 3D printing, ExoCAD, complete removable dentures.

Confocal and SEM imaging to demonstrate food pathogen- biofilm biocontrol by pyocyanin from Pseudomonas aeruginosa BTRY1

2016 ◽  
Vol 6 (01) ◽  
pp. 5218
Author(s):  
Laxmi Mohandas ◽  
Anju T. R. ◽  
Sarita G. Bhat*
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Biofilm Formation ◽  
Laser Scanning ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Antibiofilm Activity ◽  
Opportunistic Pathogens ◽  
Redox Active ◽  
Sem Imaging ◽  
The Impact

An assortment of redox-active phenazine compounds like pyocyanin with their characteristic blue-green colour are synthesized by Pseudomonas aeruginosa, Gram-negative opportunistic pathogens, which are also considered one of the most commercially valuable microorganisms. In this study, pyocyanin from Pseudomonas aeruginosa BTRY1 from food sample was assessed for its antibiofilm activity by micro titer plate assay against strong biofilm producers belonging to the genera Bacillus, Staphylococcus, Brevibacterium and Micrococcus. Pyocyanin inhibited biofilm activity in very minute concentrations. This was also confirmed by Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM). Both SEM and CLSM helped to visualize the biocontrol of biofilm formation by eight pathogens. The imaging and quantification by CLSM also established the impact of pyocyanin on biofilm-biocontrol mainly in the food industry.

scholarly journals Estimation of Vegetation-Induced Flow Resistance for Hydraulic Computations Using Airborne Laser Scanning Data

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1864
Author(s):  
Peter Mewis
Keyword(s):  
Laser Scanning ◽  
Flow Resistance ◽  
Laser Scanner ◽  
Airborne Laser Scanning ◽  
Density Parameter ◽  
Vegetation Density ◽  
Airborne Laser Scanner ◽  
Airborne Laser ◽  
Bed Roughness ◽  
Available Information

The effect of vegetation in hydraulic computations can be significant. This effect is important for flood computations. Today, the necessary terrain information for flood computations is obtained by airborne laser scanning techniques. The quality and density of the airborne laser scanning information allows for more extensive use of these data in flow computations. In this paper, known methods are improved and combined into a new simple and objective procedure to estimate the hydraulic resistance of vegetation on the flow in the field. State-of-the-art airborne laser scanner information is explored to estimate the vegetation density. The laser scanning information provides the base for the calculation of the vegetation density parameter ωp using the Beer–Lambert law. In a second step, the vegetation density is employed in a flow model to appropriately account for vegetation resistance. The use of this vegetation parameter is superior to the common method of accounting for the vegetation resistance in the bed resistance parameter for bed roughness. The proposed procedure utilizes newly available information and is demonstrated in an example. The obtained values fit very well with the values obtained in the literature. Moreover, the obtained information is very detailed. In the results, the effect of vegetation is estimated objectively without the assignment of typical values. Moreover, a more structured flow field is computed with the flood around denser vegetation, such as groups of bushes. A further thorough study based on observed flow resistance is needed.

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