This study deals with the use of VIKOR method in finding the optimal solution for a special-purpose geodetic network design. It is about a multi-criteria compromise ranking method developed in 1986. ...Based on previously defined criteria functions related to precision and reliability, four acceptable alternative solutions were firstly established. Then, with the aim of finding the optimal one, those solutions were subjected to VIKOR method. The geodetic micro-network used in this study was simulated as a trilateration one and consisted of six control points discretizing a structural geometry as well as four, five or six reference points (pillars), depending on what alternative solution it was about. The optimal network design should have ensured the detection of deviations of the control points' positions in accordance with a priori introduced tolerances and constraints. It turned out the approach based on VIKOR method is a very efficient tool in tasks involving multiple conflicting requirements referred to a geodetic engineer and in the cases when the decision must be made in a short term.
The construction of underwater geodetic networks (UGN) is crucial in marine geodesy. To provide high-precision kinematic positioning for underwater submersibles, an underwater acoustic geodetic ...network configuration of three seafloor base stations, one subsurface buoy, and one sea surface buoy is proposed. The simulation results show that, for a 3 km-deep sea, based on the proposed UGN, the submersible positioning range and positioning accuracy are primarily affected by the size of the seafloor base station array, while the height of the subsurface buoy has a greater impact on the submersible positioning accuracy than the positioning range. Considering current acoustic ranging technology, the kinematic positioning performance of the UGN is optimal when the seafloor base stations are 9~13 km apart and the subsurface buoy is less than 2.5 km above the seafloor, which can achieve a submersible positioning accuracy of less than 30 m within an underwater space of 25 km × 25 km × 3 km. The proposed cost-effective UGN configuration can provide high-precision submersible kinematic positioning performance for seafloor surveying and ocean precision engineering. The impact of the underwater environment on the acoustic transmission characteristics should be further investigated.
Topographic, geodetic and cartographic activities are one of the main activities for the effective development of the economy, science of strengthening national security and defense. It is a set of ...management, production, scientific and educational activities for the storage and communication to users of geodetic and cartographic information and data. The article considers one of the segments of this activity – the state of geodetic support of the territory of Ukraine and its assessment according to official data on the possibility of creating topographic maps and plans of scale 1:25 000 – 1:2000 in compliance with applicable regulations. To carry out the assessment, around the points of the State Geodetic Network of Ukraine (DGM) buffer zones of radii of circles of standard sizes were constructed, zoning of the territory with Thissen-Voronoi polygons and covering of the territory in the form of a hexagonal grid were done by means of ArcGIS. The results of the current assessment as of 2022 conducted by three methods are summarized in the table in terms of oblasts of Ukraine. The data obtained are compared to the previous assessment conducted five years ago. Changes in the state of geodetic support have been identified and their objective reasons explained. The advantages and disadvantages of each of the proposed methods of geoinformation analysis of the assessment of the state of geodetic support of the territories are given. It is established that the combination of different methods will allow to use the existing points of DGM with greater efficiency and to substantiate the priority places for further development of the network. The complex of scientific and applied works related to the modernization of the state geodetic network will allow to quickly and locally develop a network based on satellite and computer technologies and create and present digital cartographic information at the modern scientific and technical level in accordance with current needs.
AbstractOptimization of a geodetic network is a process in which a specific stage (or stages) is designed in such a way that the obtained result meets the assumed (optimum) design requirements. The ...goal of this article is to present a new method for designing observation plans first-order design (FOD) that aims at maximally reducing the number of observations (the cost criterion) while maintaining the a priori established quality criteria (accuracy and reliability). To achieve this goal, a categorization of points was introduced and the criteria were arranged into a hierarchy. Because the method uses computer simulation, sequential estimation was also used to speed up the computational process. The cost model is a general model defined as minimization of the number of observations in the network, regardless of their weight. The study was carried out using the example of a geodetic network designed for the National Stadium in Warsaw. The results bear out the effectiveness of reduction of observations and show the impact that strict criteria have on the scale of this reduction.
In adjusted geodetic networks, cases of local configuration defects (defects in the geometric structure of the network due to missing data or errors in point numbering) can be encountered, which lead ...to the singularity of the normal equation system in the least-squares procedure. Numbering errors in observation sets cause the computer program to define the network geometry incorrectly. Another cause of a defect may be accidental omission of certain data records, causing local indeterminacy or lowering of local reliability rates in a network. Obviously, the problem of a configuration defect may be easily detectable in networks with a small number of points. However, it becomes a real problem in large networks, where manual checking of all data becomes a very expensive task. The paper presents a new strategy for the detection of configuration defects with the use of the Tikhonov regularization method. The method was implemented in 1992 in the GEONET system (
).
In this paper, the theoretical background of the Caspary method of geodetic deformation analysis is described and implemented in a simulated geodetic network in which two epochs of measurements are ...used. The Caspary approach foresees congruence testing of the geodetic network, the determination of the stable points between two analysed epochs, the transformation of the geodetic network using S-transformation, the calculation of displacements, and, in the last step, the graphical presentation of displacement vectors. Results obtained from the presented example are similar to those presented in the Hannover, Karlsruhe, Delft, Fredericton, München, and robust methods.
Processos de subsidência são caracterizados pelo movimento de uma porção da superfície da Terra na qual resulta no rebaixamento do terreno. Os ambientes sedimentares deposicionais, como é o caso dos ...deltas, são propensos à subsidência devido à compactação de sedimentos. O objetivo principal deste trabalho é o desenvolvimento de um projeto geométrico e implantação de uma rede geodésica para o acompanhamento periódico da subsidência na planície deltaica do Rio São Francisco. Cordões litorâneos holocênicos presentes na planície tiveram suas altitudes avaliadas a partir de perfis topográficos longitudinais obtidos por levantamentos GNSS (Global Navigation Satellite System). Em alguns cordões, desníveis médios na ordem de 3,2 m e 5,5 m foram detectados na porções sul e norte da planície, respectivamente, sendo um indicativo de rebaixamento da superfície devido a acentuados processos de subsidência que ocorreram desde o holoceno. As informações de rebaixamento dos cordões permitiram identificar áreas vulneráveis aos processos de subsidência, dando suporte ao projeto de uma rede geodésica composta por 26 vértices de monitoramento.
Monitoring displacements of the object can be performed using geodetic methods by selecting reference points on the surrounding terrain and points on the object that discretely describe the object’s ...behavior. The measurements are repeated in several epochs. By analyzing the geodetic network we can determine the status of a single point, i.e., whether the point has moved or not. The article discusses the testing of congruence, the testing of transformation of a single triangle, and the calculation of other deformation parameters in 2D networks resulting from the changes of points coordinates between two epochs. This is essentially the content of the Munich deformation method presented by W.M. Welsch, which includes the X- and L-method. The article also proposes some corrections to the original Munich approach. Finally, the applicability of the method is shown on a well-known practical example.
The ranges derived from acoustic measurements between seafloor stations are relatively more accurate compared with those derived from the sea surface vessel transducer to the seafloor transponders, ...because measurements through mixed water layers will be affected by complex acoustic range errors. Coordinates of seafloor stations can be improved by the direct-path acoustic ranging. Systematic errors in acoustic rangings, however, will significantly deteriorate the accuracy of vertical coordinates. In order to mitigate the effects of these systematic errors (e.g., acoustic ray bending and sound speed variation errors in acoustic measurements on the seafloor station location parameters), the observation model needs to be finely constructed. First, a new observation model with acoustic ray bending and sound speed bias parameters is established. Then, using a seafloor geodetic network with four moored stations at a depth of about 3000 m in the South China Sea, the significance of the acoustic ray bending parameter is tested. The results show that (1) the acoustic ray bending parameter is significant at the 90% confidence level, which means that the acoustic ray bending error in the seafloor geodetic network is not negligible; (2) by estimating the coefficient of acoustic ray bending, the influence of the acoustic ray bending error on the vertical coordinate components can be significantly mitigated; our model improves the accuracy of the seafloor stations' position with differences in the horizontal coordinate components less than 0.1 cm between the two-dimensional adjustment and three-dimensional adjustment, and also improves the vertical coordinate component to uncertainty less than 3.0 cm; (3) the relative movement between the moored stations is less than 50 cm, and the horizontal movement is larger than the vertical movement.
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