TLS is nowadays often used for deformation monitoring. As it is not able to scan identical points in different time epochs, mathematical models of objects derived from point clouds have to be used. ...The most common geometric form to describe built objects is a plane, which can be described by four parameters. In this study, we aimed to find out how small changes in the parameters of the plane can be detected by TLS. We aimed to eliminate all possible factors that influence the scanning. Then, we shifted and tilted a finite physical representation of a plane in a controlled way. After each controlled change, the board was scanned several times and the parameters of the plane were calculated. We used two different types of scanning devices and compared their performance. The changes in the plane parameters were compared with the actual change values and statistically tested. The results show that TLS detects shifts in the millimetre range and tilts of 150″ (for a 1 m plane). A robotic total station can achieve twice the precision of TLS despite lower density and slower performance. For deformation monitoring, we strongly recommend repeating each scan several times (i) to check for gross errors and (ii) to obtain a realistic precision estimate.
This article discusses the method of computing the values of the unknowns under the condition of the minimum sum of the squares of the residuals of the observations, also known as the least squares ...method, with the additional condition of taking into account the errors in the unknowns. The problem has already been treated by many authors, especially in the field of regression analysis and the computation of transformation parameters. We give an overview of the theoretical foundations of the least squares method and extensions of this method by considering the errors in the unknowns in the model matrix. So, the total least squares method is presented in this paper, fitting the regression line to a set of points and computing transformation parameters for the transition between the old and the new Slovenian national coordinate systems. Furthermore, for the first time, the method is also presented and tested in the S-transformation between different geodetic datum-dependent solutions. Also, for the first time, we systematically compare the results of the approach with conventional approaches in all three considered tasks. With the results based on relevant statistics, we confirm the suitability of the described method for dealing with the considered computational tasks.
Despite the technical progress monitoring the stability of engineering structures remains one of the most difficult tasks in engineering geodesy. This article presents the deformation analysis ...according to the Munich approach of W. M. Welsch. The method deals with the testing of the geodetic network's congruence, the affinity of selected triangles, and the testing of other kinematic parameters in 2D geodetic networks. Deformation analysis using the Munich approach can be performed using the X-method, which is based on the comparison of the coordinates of identical points in the geodetic network between two sets of measurements that depend on the geodetic datum, or using the L-method, which determines changes in the values of lengths and angles which are quantities independent of the geodetic datum. In the modified method, we propose to determine the congruence of all lengths and all angles in the network between two sets of measurements and to determine the congruence of all triangles between points in the network, not only selected ones, as it is common in the classical approach of deformation analysis based on the Munich approach. The proposed improvements are tested on the example of a known hexagon, and an analysis is made of the success of detecting stable points in the network using the classical Munich approach. In the present case, the results of the proposed method did not differ from the results of other deformation analysis methods.
In geodesy, statistical testing aids in determining the extent to which the criteria and requirements needed in the measurement and calculation proceedings have been fulfilled. A “rule of thumb” ...method that compares test statistics to constants Tcrit = 3 or Tcrit = 5 has been established. The test statistic T is the ratio between the displacement and its precision. Since it is not distributed through any of the known distribution functions, (statistical) simulations are used to assess the empirical distribution in 2D and 3D geodetic networks. The proposed alternative procedure leads to a more precise detection of significant displacements at a given test significance level α. Regardless of the network's dimensionality, Tcrit obtains the value of 3 at a risk level below 1%. When 5% is considered to be an acceptable risk level, the critical value can be lower than 3 or 5. Thus, significant displacements should be considered with regard to the acceptable risk level and not according to the usual “rule of thumb”.
This study evaluates the applicability of different models of coordinate transformation between local and global geodetic datums. The results indicate the grid-based method as the best solution, ...assuming a sufficient density of tie points. Transformation based on a limited number of tie points, which do not reflect the real state of the survey basis in a particular area, have limited possibilities to reduce nonuniform and unequally distributed distortions that are usually found in the spatial data. This inevitably leads to the degradation of accuracy of transformation results, which is unacceptable. By using the optimal resolution grid model, which includes geodetic points from the area of the cadastral municipality that is being transformed, much better results are achieved compared to the model of distortion shifts used in the Federation of Bosnia and Herzegovina.
2020 ABSTRACT Although they have long been regarded as obsolete, classical electronic theodolites, which are made as standalone anglemeasuring instruments, are still being produced and widely used ...throughout the world. A detailed analysis of the theodolite 's purpose, accuracy, construction, capabilities and functionality has resulted in the determination of three main groups of these instruments; a brief description of each category is provided. KEY WORDS electronic theodolite, development, classification, survey technology 1 UVOD V šestdesetih letih 20. stoletja so bili v tedanji Zahodni Nemčiji uspešno skonstruirani prvi instrumenti z elektronskim sistemom za čitanje in registracijo kotnih vrednosti na steklenih limbih teodolitov (Zwickert, 1964; Zetche, 1968). Čeprav so tovarne Fennel, Breithaupt, W. & L. E. Gurley in MOM opustile nadaljnji razvoj in proizvodnjo elektronskih teodolitov, lahko rečemo, da programi razvoja njihovih elektronskih teodolitov niso bili zaman in so opravili svoje poslanstvo.
In geodesy, reliable results are obtained with quality observations and the corresponding mathematical and stochastic models. One establishes if individual criteria and requirements during the ...measurement and calculation procedures are met by evaluating and testing typical parameters respectively -- procedures of statistical hypothesis testing being indispensable part of the process. In deformation analysis, statistical tests are applied for testing the assumptions about the parameters, for assessing the conformity of observations and the mathematical model, for detecting of gross errors in observations for identifying the conformity of allegedly fixed points between the epochs and for determining the points with statistically typical displacements. For the processing of quality measurement data, the task of a surveyor is to use a correct and reliable mathematical model, which provides a high degree of confidence in the results and reduces a client's risk. Methods of statistical hypothesis testing help experts to make decisions, but it is not possible to use them to replace measurement and calculation procedures in geodesy.
Deformation analysis using the Munich approach can be performed using the X-method, which is based on the comparison of the coordinates of identical points in the geodetic network between two sets of ...measurements that depend on the geodetic datum, or using the L-method, which determines changes in the values of lengths and angles which are quantities independent of the geodetic datum. KEY WORDS deformation analysis, Munich approach, modified method, X-method, L-method, testing of congruence, strain analysis of triangles 1INTRODUCTION Monitoring the stability of engineering structures or natural objects is the systematic measurement and tracking of changes in the shape and/or dimensions of the object in question as a result of loads. ...we examine the changes in the datum-independent lengths in the network, as suggested by the author of the W. M. Welsch method, and in this way discover the points that have moved in a statistically significant way (Welsch and Zhang, 1983; Ašanin, 1986). According to the two methods of deformation analysis based on the Munich approach, i.e. according to the X-method and according to the L-method, exactly the same results are obtained in the phase of testing of congruence of the geodetic network and the phase of testing of affinity of the geodesic network (Welsch, 1983; Welsch and Zhang, 1983; Soldo and Ambrožič, 2018), therefore, in the proposed modified method, we will use only the X-method for testing of congruence and testing of affinity of the geodetic network. 2DEFORMATION ANALYSIS ACCORDING TO THE MUNICH APPROACH 2.1Prerequisites for the performance of deformation analyses To perform deformation analysis, it is important to ensure the quality and consistency of measurement accuracy between two sets of measurements.
This article presents a method for measuring the geometry of crane rails with terrestrial laser scanning (TLS). Two sets of crane rails were divided into segments, their planes were adjusted, and the ...characteristic rail lines were defined. We used their profiles to define the positional and altitude deviations of the rails, the span and height difference between the two rails, and we also verified that they complied with the Eurocode 3 standard. We tested the method on crane rails at the hydroelectric power plant in Krško and the thermal power plant in Brestanica. We used two scanning techniques: "pure" TLS (Riegel VZ-400) and "hybrid" TLS (Leica MS50) scanning. This article's original contribution lies in the detailed presentation of the computations used to define the characteristic lines of the rails without using the numeric procedures from existing software packages. We also analysed the influence of segment length and point density on the rail geometry results, and compared the two laser scanning techniques. We also compared the results obtained by terrestrial laser scanning with the results obtained from the classic polar method, which served as a reference point for its precision.
PDF