Modelling the Surface of Racing Vessel’s Hull by Laser Scanning and Digital Photogrammetry

The knowledge of the hull shape and geometry of a racing vessel is one of the most important factors for predicting boat performance. The Offshore Racing Congress (ORC) rating system specifies the calculation parameters of the hydrodynamic forces of boat lift and drag on the basis of input data as the length of waterline while sailing, displacement, wetted surface and the volume distribution along the hull. It is represented by sophisticated calculations for national as well as international events and races. Measurement using a reflectorless total station in a coordinate system defined by the sailboat hull is the most established method approved by the ORC organisation. The determination of these geometric parameters by new, unconventional technologies, which should provide a quicker and more detailed measurement while preserving the quality and accuracy of results necessary for the handicap calculations was our main objective. Geometrical shapes of a cabin sailboat hull were determined by the technology of terrestrial laser scanning and two methods of digital close-range photogrammetry—convergence case of photogrammetry and Structure-from-Motion (SfM) method. High-Definition Surveying (HDS) targets for laser scanning and coded targets for digital photogrammetry were used throughout all methods in order to transform the resulting data into a single local coordinate system. The resulting models were mutually compared by visual, geometrical and statistical comparison. In conclusion, both technologies were considered suitable, however, with various advantages and disadvantages. Nevertheless, although labour intensive, the SfM photogrammetry can be considered the most suitable method if the correct procedures are followed.

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Three-Dimensional Linear Restoration of a Tunnel Based on Measured Track and Uncontrolled Mobile Laser Scanning

Sensors ◽

10.3390/s21113815 ◽

2021 ◽

Vol 21 (11) ◽

pp. 3815

Author(s):

Yulong Han ◽

Haili Sun ◽

Ruofei Zhong

Keyword(s):

Coordinate System ◽

Point Cloud ◽

Laser Scanning ◽

Large Scale ◽

Local Coordinate System ◽

Vertical Direction ◽

Measurement Technology ◽

Subway Tunnel ◽

Average Deviation ◽

Design Data

Traditional precision measurement adopts discrete artificial static observation, which cannot meet the demands of the dynamic, continuous, fine and high-precision holographic measurement of large-scale infrastructure construction and complex operation and maintenance management. Due to its advantages of fast, accurate and convenient measurement, mobile laser scanning technology is becoming a popular technology in the maintenance and measurement of infrastructure construction such as tunnels. However, in some environments without satellite signals, such as indoor areas and underground spaces, it is difficult to obtain 3D data by means of mobile measurement technology. This paper proposes a method to restore the linear of the point cloud obtained by mobile laser scanning based on the measured track center line. In this paper, the measured track position is interpolated with a cubic spline to calculate the translations, and the rotation parameters are calculated by combining the simulation design data. The point cloud of the cross-section of the tunnel under the local coordinate system is converted to the absolute coordinate system to calculate the tunnel line. In addition, the method is verified by experiments combined with the subway tunnel data, and the overall point error can be controlled to within 0.1 m. The average deviation in the horizontal direction is 0.0551 m, and that in the vertical direction is 0.0274 m. Compared with the previous methods, this method can effectively avoid the obvious deformation of the tunnel and the sharp increase in the error, and can process the tunnel point cloud data more accurately and quickly. It also provides better data support for subsequent tunnel analysis such as 3D display, completion survey, systematic hazard management and so on.

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Absolute Positioning and Orientation of MLSS in a Subway Tunnel Based on Sparse Point-Assisted DR

Sensors ◽

10.3390/s20030645 ◽

2020 ◽

Vol 20 (3) ◽

pp. 645

Author(s):

Qian Wang ◽

Chao Tang ◽

Cuijun Dong ◽

Qingzhou Mao ◽

Fei Tang ◽

...

Keyword(s):

Coordinate System ◽

Laser Scanning ◽

Local Coordinate System ◽

Point Clouds ◽

Measurement Unit ◽

Scanning System ◽

Control Points ◽

Starting Point ◽

Inspection Work ◽

Subway Tunnels

When performing the inspection of subway tunnels, there is an immense amount of data to be collected and the time available for inspection is short; however, the requirement for inspection accuracy is high. In this study, a mobile laser scanning system (MLSS) was used for the inspection of subway tunnels, and the key technology of the positioning and orientation system (POS) was investigated. We utilized the inertial measurement unit (IMU) and the odometer as the core sensors of the POS. The initial attitude of the MLSS was obtained by using a static initial alignment method. Considering that there is no global navigation satellite system (GNSS) signal in a subway, the forward and backward dead reckoning (DR) algorithm was used to calculate the positions and attitudes of the MLSS from any starting point in two directions. While the MLSS passed by the control points distributed on both sides of the track, the local coordinates of the control points were transmitted to the center of the MLSS by using the ranging information of the laser scanner. Then, a four-parameter transformation method was used to correct the error of the POS and transform the 3-D state information of the MLSS from a navigation coordinate system (NCS) to a local coordinate system (LCS). This method can completely eliminate a MLSS’s dependence on GNSS signals, and the obtained positioning and attitude information can be used for point cloud data fusion to directly obtain the coordinates in the LCS. In a tunnel of the Beijing–Zhangjiakou high-speed railway, when the distance interval of the control points used for correction was 120 m, the accuracy of the 3-D coordinates of the point clouds was 8 mm, and the experiment also showed that it takes less than 4 h to complete all the inspection work for a 5–6 km long tunnel. Further, the results from the inspection work of Wuhan subway lines showed that when the distance intervals of the control points used for correction were 60 m, 120 m, 240 m, and 480 m, the accuracies of the 3-D coordinates of the point clouds in the local coordinate system were 4 mm, 6 mm, 7 mm, and 8 mm, respectively.

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A NOVEL OF COMPARISON BETWEEN 3D HIGH DEFINITION MAPS CREATED BY PHOTOGRAMMETRY AND LASER SCANNING APPLIED FOR AN AUTONOMOUS VEHICLE

Vietnam Journal of Science and Technology ◽

10.15625/2525-2518/59/3/15848 ◽

2021 ◽

Vol 59 (3) ◽

pp. 402

Author(s):

Nang Xuan Ho

Keyword(s):

High Resolution ◽

Optical Imaging ◽

Laser Scanning ◽

Autonomous Vehicle ◽

Mapping Method ◽

Imaging Method ◽

High Definition ◽

Mathematical Algorithm ◽

Advantages And Disadvantages ◽

High Resolution Map

In this paper, based on the selected mathematical algorithm, the performing of two methods for building high-resolution 3D maps that are Photographmetry and Laser scanning was analyzed to find out the advantages and disadvantages of each one. The results showed that the high-resolution map constructed by using lidar was more accurate and detailed, whereas the map constructed by using images with coordinates was more intuitive. A mapping method using lidar-camera fusion was proposed in which the detailed roads are created by Lidar and the rest area built by optical imaging method.

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Outlier detection by the EM algorithm for laser scanning in rectangular and polar coordinate systems

Journal of Applied Geodesy ◽

10.1515/jag-2015-0004 ◽

2015 ◽

Vol 9 (3) ◽

Cited By ~ 3

Author(s):

Karl-Rudolf Koch ◽

Boris Kargoll

Keyword(s):

Em Algorithm ◽

Coordinate System ◽

Linear Model ◽

Laser Scanning ◽

Local Coordinate System ◽

Polar Coordinates ◽

Polar Coordinate System ◽

Coordinate Systems ◽

The Em Algorithm ◽

Polar Coordinate

AbstractTo visualize the surface of an object, laser scanners determine the rectangular coordinates of points of a grid on the surface of the object in a local coordinate system. Vertical angles, horizontal angles and distances of a polar coordinate system are measured with the scanning. Outliers generally occur as gross errors in the distances. It is therefore investigated here whether rectangular or polar coordinates are better suited for the detection of outliers. The parameters of a surface represented by a polynomial are estimated in the nonlinear Gauss Helmert (GH) model and in a linear model. Rectangular and polar coordinates are used, and it is shown that the results for both coordinate systems are identical. It turns out that the linear model is sufficient to estimate the parameters of the polynomial surface. Outliers are therefore identified in the linear model by the expectation maximization (EM) algorithm for the variance-inflation model and are confirmed by the EM algorithm for the mean-shift model. Again, rectangular and polar coordinates are used. The same outliers are identified in both coordinate systems.

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ACCURACY ASSESSMENT OF POINT CLOUDS GEO-REFERENCING IN SURVEYING AND DOCUMENTATION OF HISTORICAL COMPLEXES

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xlii-5-w1-161-2017 ◽

2017 ◽

Vol XLII-5/W1 ◽

pp. 161-165 ◽

Cited By ~ 2

Author(s):

A. Fryskowska

Keyword(s):

Coordinate System ◽

Laser Scanning ◽

Accuracy Assessment ◽

Local Coordinate System ◽

Three Dimensional ◽

Point Clouds ◽

Digital Culture ◽

Global Coordinate System ◽

Registration Accuracy ◽

Factors Affecting

Terrestrial Laser Scanning (TLS) technique is widely used for documentation and preservation of historical sites by for example creating three-dimensional (3-D) digital models or vectorial sketches. In consequence, a complex, complete, detail and accurate documentation of historical structure is created. It is very crucial when it comes about modern digital culture. If we acquire TLS data of once particular structure usually we do it in local coordinate system of scanner. Nevertheless when measurements are conducted for complex of several historical buildings or monuments (i.e. castle ruins, building of narrow streets of the Old Towns), the registration of point clouds into a common, global coordinate system is one of the critical steps in TLS data processing. Then we have integrate data with different accuracy level. Inner accuracy of local coordinate system (scanner system) is usually thrice higher than for global coordinate systems measurement. The paper describes the geometric quality of the direct georeferencing in post-processing, considering surveying points. Then, an analysis of factors affecting registration accuracy is proposed. Finally, an improvement of direct georeferencing technique is presented and examined. Furthermore, registered data and chosen orientation methods have been compared to each other.

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Establishment of local coordinate systems in the transition to the geodetic system of coordinates of GSK-2011

Geodesy and Cartography ◽

10.22389/0016-7126-2017-929-11-2-10 ◽

2017 ◽

Vol 929 (11) ◽

pp. 2-10

Author(s):

A.V. Vinogradov

Keyword(s):

Coordinate System ◽

Small Businesses ◽

Transition Period ◽

Local Coordinate System ◽

Initial Point ◽

Central Meridian ◽

Administrative District ◽

Local Networks ◽

Small Areas ◽

Geodetic System

Pretty before long there will be transition to the geodetic system of coordinates of GSK-2011. For the transition period it is necessary to develop a method of recalculating coordinates from one system to another. The existing methods of recalculating coordinates are designed for recalculating coordinate points of state geodetic networks (GGS) and geodetic local networks (GSS). For small areas (administrative districts, populated areas) simplified methods are more acceptable. You need to choose the resampling methods that can be applied in small businesses, performing surveying works. The article presents the the results of calculations of changes of coordinates of the same point in GSK-2011 and SC-95 in six-degree zones of Gauss projection. It was found that in each region values of the shifts changed to small ones. Therefore, it is possible to convert the coordinates of the points by the simplified formulae. For recalculation from the coordinates of GSK-2011 in SK-95 or local coordinate system (WCS) of the administrative district it is necessary to find the origin of coordinates, scale value and rotation of the coordinate axes. The error of the conversion shall not exceed 0,001 m. The coordinates of the initial point of the local coordinate system relative to the central meridian of the local coordinate system shall be added in the list of parameters of the transition from local coordinate system to the state one.

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Consistent co-rotational framework for Euler-Bernoulli and Timoshenko beam-column elements under distributed member loads

Advances in Structural Engineering ◽

10.1177/1369433220986632 ◽

2021 ◽

pp. 136943322098663

Author(s):

Yi-Qun Tang ◽

Wen-Feng Chen ◽

Yao-Peng Liu ◽

Siu-Lai Chan

Keyword(s):

Coordinate System ◽

Stiffness Matrix ◽

Traditional Method ◽

Local Coordinate System ◽

Frame Structures ◽

Global Coordinate System ◽

Single Element ◽

Geometrically Nonlinear ◽

Geometrically Nonlinear Analysis ◽

Geometric Stiffness

Conventional co-rotational formulations for geometrically nonlinear analysis are based on the assumption that the finite element is only subjected to nodal loads and as a result, they are not accurate for the elements under distributed member loads. The magnitude and direction of member loads are treated as constant in the global coordinate system, but they are essentially varying in the local coordinate system for the element undergoing a large rigid body rotation, leading to the change of nodal moments at element ends. Thus, there is a need to improve the co-rotational formulations to allow for the effect. This paper proposes a new consistent co-rotational formulation for both Euler-Bernoulli and Timoshenko two-dimensional beam-column elements subjected to distributed member loads. It is found that the equivalent nodal moments are affected by the element geometric change and consequently contribute to a part of geometric stiffness matrix. From this study, the results of both eigenvalue buckling and second-order direct analyses will be significantly improved. Several examples are used to verify the proposed formulation with comparison of the traditional method, which demonstrate the accuracy and reliability of the proposed method in buckling analysis of frame structures under distributed member loads using a single element per member.

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MEASUREMENT OF VERTICALITY CONSTRUCTION OF BUSHINGS FOR LABORATORY CONSTRUCTION MATERIALS

Geodesy and Cartography ◽

10.3846/20296991.2014.987458 ◽

2014 ◽

Vol 40 (4) ◽

pp. 171-174 ◽

Cited By ~ 1

Author(s):

Petr Jadviščok ◽

Rostislav Dandoš ◽

Tomaš Jiroušek

Keyword(s):

Coordinate System ◽

Building Materials ◽

Civil Engineering ◽

Local Coordinate System ◽

Construction Materials ◽

Polar Method ◽

Standard Equipment ◽

Final Number ◽

Loading Tests ◽

Design And Manufacture

This contribution describes process which was used for verticality measurement of the bushings for laboratory construction materials in the pavilion of testing. This pavilion is newly built in VŠB-TU Ostrava, Faculty of Civil Engineering, as part of the Testing house of the building materials. The requirement of the building investor was to determine the verticality of the bushings placed between the first aboveground and the first underground floor. After the building finishing, the bushings with the diameter 70 mm will be used for loading tests of various building materials. The final number of bushings is 169, and they are placed lengthwise and crosswise in the step of 750 mm. The centres of the bushings were measured by polar method in pavilion local coordinate system. The precision of the bushing centres determination was }5 mm according to the investor´s requirement. The precision would not be followed if the standard equipment for reflector fixing was used. In that case, it was necessary to design and manufacture special tool in the shape of truncated cone. On the top part was placed central pivot for reflector with additional plate bubble.

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Computation of electrostatic fields in anisotropic human tissues using the Finite Integration Technique (FIT)

Advances in Radio Science ◽

10.5194/ars-2-309-2004 ◽

2005 ◽

Vol 2 ◽

pp. 309-313 ◽

Cited By ~ 3

Author(s):

V. C. Motresc ◽

U. van Rienen

Keyword(s):

Coordinate System ◽

Electromagnetic Fields ◽

Human Body ◽

Local Coordinate System ◽

Anisotropic Materials ◽

The Body ◽

Integration Technique ◽

Data Set ◽

Computer Data ◽

Finite Integration Technique

Abstract. The exposure of human body to electromagnetic fields has in the recent years become a matter of great interest for scientists working in the area of biology and biomedicine. Due to the difficulty of performing measurements, accurate models of the human body, in the form of a computer data set, are used for computations of the fields inside the body by employing numerical methods such as the method used for our calculations, namely the Finite Integration Technique (FIT). A fact that has to be taken into account when computing electromagnetic fields in the human body is that some tissue classes, i.e. cardiac and skeletal muscles, have higher electrical conductivity and permittivity along fibers rather than across them. This property leads to diagonal conductivity and permittivity tensors only when expressing them in a local coordinate system while in a global coordinate system they become full tensors. The Finite Integration Technique (FIT) in its classical form can handle diagonally anisotropic materials quite effectively but it needed an extension for handling fully anisotropic materials. New electric voltages were placed on the grid and a new averaging method of conductivity and permittivity on the grid was found. In this paper, we present results from electrostatic computations performed with the extended version of FIT for fully anisotropic materials.

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EXPLORING ALS AND DIM DATA FOR SEMANTIC SEGMENTATION USING CNNS

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xlii-1-347-2018 ◽

2018 ◽

Vol XLII-1 ◽

pp. 347-354 ◽

Cited By ~ 5

Author(s):

F. Politz ◽

M. Sester

Keyword(s):

Point Cloud ◽

Laser Scanning ◽

Semantic Segmentation ◽

Point Clouds ◽

Good Alternative ◽

Aerial Images ◽

Learning Approaches ◽

Advantages And Disadvantages ◽

Sensing Applications ◽

High Level

Abstract. Over the past years, the algorithms for dense image matching (DIM) to obtain point clouds from aerial images improved significantly. Consequently, DIM point clouds are now a good alternative to the established Airborne Laser Scanning (ALS) point clouds for remote sensing applications. In order to derive high-level applications such as digital terrain models or city models, each point within a point cloud must be assigned a class label. Usually, ALS and DIM are labelled with different classifiers due to their varying characteristics. In this work, we explore both point cloud types in a fully convolutional encoder-decoder network, which learns to classify ALS as well as DIM point clouds. As input, we project the point clouds onto a 2D image raster plane and calculate the minimal, average and maximal height values for each raster cell. The network then differentiates between the classes ground, non-ground, building and no data. We test our network in six training setups using only one point cloud type, both point clouds as well as several transfer-learning approaches. We quantitatively and qualitatively compare all results and discuss the advantages and disadvantages of all setups. The best network achieves an overall accuracy of 96% in an ALS and 83% in a DIM test set.

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