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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

An assessment of using least squares adjustment to upgrade spatial data in GIS

Merritt, Roger, Surveying & Spatial Information Systems, Faculty of Engineering, UNSW January 2005 (has links)
The GIS Industry has digitised cadastre from the best available paper maps over the last few decades, incorporating the inherent errors in those paper maps and in the digitising process. The advent of Global Positioning Systems, modern surveying instruments and advances in the computing industry has made it desirable and affordable to upgrade the placement, in terms of absolute and relative position) of these digital cadastres. The Utility Industry has used GIS software to place their assets relative to these digital cadastres, and are now finding their assets placed incorrectly when viewed against these upgraded digital cadastres. This thesis examines the processes developed in the software program called the ???Spatial Adjustment Engine???, and documents a holistic approach to semi-automating the upgrading of the digital cadastre and the subsequent upgrading of the utility assets. This thesis also documents the various pilot projects undertaken during the development of the Spatial Adjustment Engine, the topological scenarios found in each pilot, their solution, and provides a framework of definitions needed to explore this field further. The results of each pilot project are given in context, and lead to the conclusions. The conclusions indicate the processes and procedures implemented in the Spatial Adjustment Engine are a suitable mechanism for the upgrade of digital cadastre and of spatially dependant themes such as utility assets, zoning themes, annotation layers, and some road centreline themes.
2

An assessment of using least squares adjustment to upgrade spatial data in GIS

Merritt, Roger, Surveying & Spatial Information Systems, Faculty of Engineering, UNSW January 2005 (has links)
The GIS Industry has digitised cadastre from the best available paper maps over the last few decades, incorporating the inherent errors in those paper maps and in the digitising process. The advent of Global Positioning Systems, modern surveying instruments and advances in the computing industry has made it desirable and affordable to upgrade the placement, in terms of absolute and relative position) of these digital cadastres. The Utility Industry has used GIS software to place their assets relative to these digital cadastres, and are now finding their assets placed incorrectly when viewed against these upgraded digital cadastres. This thesis examines the processes developed in the software program called the ???Spatial Adjustment Engine???, and documents a holistic approach to semi-automating the upgrading of the digital cadastre and the subsequent upgrading of the utility assets. This thesis also documents the various pilot projects undertaken during the development of the Spatial Adjustment Engine, the topological scenarios found in each pilot, their solution, and provides a framework of definitions needed to explore this field further. The results of each pilot project are given in context, and lead to the conclusions. The conclusions indicate the processes and procedures implemented in the Spatial Adjustment Engine are a suitable mechanism for the upgrade of digital cadastre and of spatially dependant themes such as utility assets, zoning themes, annotation layers, and some road centreline themes.
3

Desarrollo y análisis de un sistema para la determinación de la dinámica del movimiento más general de la azotea de un edificio de gran altura y su evolución en el tiempo

Quesada Olmo, María Nieves 01 December 2019 (has links)
[EN] The goal of this research is to analise and to develop a system that allows the determination of the most general movement dynamics of a tall building, as well as to quantify its evolution over time by means of Gaussian algorithms revision and by applying GNSS techniques and methodologies. In this thesis, the oscillation of the control quadrilateral located on the roof of the ``Torre Espacio'' bulding and determined by a high precision survey network is assessed rigorously with the method of sequential solution with addition of variables or parameters using VRS-RTK techniques. It is the data processing, together with the gaussian adjustment methodology based on a conditional tax own physical reality and analysis of partial and final results allowing us to achieve a high level of confidence that translates into effective management real-time risk. In parallel, the instantaneous and simultaneous precision of each antenna in every moment is determined. That is the error surface and the individual, simultaneous reliability of each GNSS receiver. Prior to assessing the structure dynamics, the sensitivity threshold is computed, under which nothing can be affirmed or denied with respect to the displacement produced in the control structure. It involves testing the accuracy of the instrumentation GNSS and gaussian initial adjustment mathematical model. The project concludes with the development of a warning system that is activated at the time when the movement of the building reaches a preset threshold. / [ES] El objeto de la investigación es analizar y desarrollar un sistema que permita determinar la dinámica más general del movimiento de un edificio de gran altura, así como cuantificar su evolución en el tiempo. Dicho sistema se plantea mediante la revisión de los algoritmos gaussianos y la aplicación de metodologías y técnicas GNSS. En este trabajo se determina rigurosamente, mediante el método general de Ajustes Coordinados con adición de funciones de variables o parámetros, la situación de oscilación del cuadrilátero de control conformado por una red microgeodésica local y observado con técnicas VRS-RTK ubicado en la planta de coronación del edificio Torre Espacio de Madrid. Es precisamente el tratamiento de los datos, la metodología gaussiana de ajuste en función de un condicionado propio impuesto por la realidad física y el análisis de los resultados parciales y finales lo que nos permite alcanzar un alto nivel de fiabilidad que se traduce en una gestión eficaz del riesgo en tiempo real. Paralelamente se determina la precisión instantánea y simultánea de cada antena y en cada momento, esto es la superficie de error y la fiabilidad individual y simultánea de la posición de cada receptor GNSS. Previo a la evaluación de la dinámica de la estructura, se calcula el umbral de precisión o ``sensibilidad'', por debajo del cual nada puede afirmarse o negarse con respecto al desplazamiento producido en la estructura a controlar. Supone contrastar la precisión de la instrumentación GNSS y del modelo matemático inicial de ajuste gaussiano. El proyecto concluye con el desarrollo de un sistema de alerta que se activa en el momento en que el movimiento del edificio alcanza un umbral preestablecido. / [CAT] L'objecte de la investigació és analitzar i desenvolupar un sistema que permeta determinar la dinàmica més general del moviment d'un edifici de gran alçada, així com quantificar la seua evoluvió en el temps. Aquest sistema es plantaja mitjançant la revisió dels algorismes Gaussians i l'aplicació de metodologies y tècniques GNSS. En aquest treball es determina rigorosament, mitjançant el mètode general d'Ajusts Coordinats amb adició de de funcions de variables o paràmetres, la situació d'oscilació del quadrilàter de control conformat per una xarxa microgeodèsica local i observant amb tècniques VRS-RTK localitzat a la planta de coronació de l'edifici TorreEspacio de Madrid. És precisament el tractament de les dades, la metodologia Gaussiana d'ajust en funció d'un condicionat propi imposat per la realitat física y l'anàlisi dels resultats parcials i finals el que ens permet arribar a un alt nivell de fiabilitat, que es tradieix en una gestió eficaç del risc en temps real. Paral·lelament es determina la precisió instantània i simultània de cada antena i en cada moment, es a dir la superfície d'error i la fiabilitat individual i simultània de la posició de cada receptor GNSS. Previament a l'evaluació de la dinàmica de l'estructura, es calcula l'umbral de precisió o ``sensibilitat'', per davall de la qual no es por afirmar o negar res respecte al desplaçament produït en l'estructura a controlar. Això suposa contrastar la precisió de la instrumentació GNSS i del model matemàtic inicial d'ajust Gaussià. El projecte conclou amb el desenvolupament d'un sistema d'alerta que s'activa en el moment en que el moviment de l'edifici arriba a un umbral preestablert. / Quesada Olmo, MN. (2015). Desarrollo y análisis de un sistema para la determinación de la dinámica del movimiento más general de la azotea de un edificio de gran altura y su evolución en el tiempo [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/58993 / TESIS
4

The 3σ-rule for outlier detection from the viewpoint of geodetic adjustment

Lehmann, Rüdiger 21 January 2015 (has links) (PDF)
The so-called 3σ-rule is a simple and widely used heuristic for outlier detection. This term is a generic term of some statistical hypothesis tests whose test statistics are known as normalized or studentized residuals. The conditions, under which this rule is statistically substantiated, were analyzed, and the extent it applies to geodetic least-squares adjustment was investigated. Then, the efficiency or non-efficiency of this method was analyzed and demonstrated on the example of repeated observations. / Die sogenannte 3σ-Regel ist eine einfache und weit verbreitete Heuristik für die Ausreißererkennung. Sie ist ein Oberbegriff für einige statistische Hypothesentests, deren Teststatistiken als normierte oder studentisierte Verbesserungen bezeichnet werden. Die Bedingungen, unter denen diese Regel statistisch begründet ist, werden analysiert. Es wird untersucht, inwieweit diese Regel auf geodätische Ausgleichungsprobleme anwendbar ist. Die Effizienz oder Nichteffizienz dieser Methode wird analysiert und demonstriert am Beispiel von Wiederholungsmessungen.
5

The 3σ-rule for outlier detection from the viewpoint of geodetic adjustment

Lehmann, Rüdiger January 2013 (has links)
The so-called 3σ-rule is a simple and widely used heuristic for outlier detection. This term is a generic term of some statistical hypothesis tests whose test statistics are known as normalized or studentized residuals. The conditions, under which this rule is statistically substantiated, were analyzed, and the extent it applies to geodetic least-squares adjustment was investigated. Then, the efficiency or non-efficiency of this method was analyzed and demonstrated on the example of repeated observations. / Die sogenannte 3σ-Regel ist eine einfache und weit verbreitete Heuristik für die Ausreißererkennung. Sie ist ein Oberbegriff für einige statistische Hypothesentests, deren Teststatistiken als normierte oder studentisierte Verbesserungen bezeichnet werden. Die Bedingungen, unter denen diese Regel statistisch begründet ist, werden analysiert. Es wird untersucht, inwieweit diese Regel auf geodätische Ausgleichungsprobleme anwendbar ist. Die Effizienz oder Nichteffizienz dieser Methode wird analysiert und demonstriert am Beispiel von Wiederholungsmessungen.
6

Alternative Approaches for the Registration of Terrestrial Laser Scanners Data using Linear/Planar Features

Dewen Shi (9731966) 15 December 2020 (has links)
<p>Static terrestrial laser scanners have been increasingly used in three-dimensional data acquisition since it can rapidly provide accurate measurements with high resolution. Several scans from multiple viewpoints are necessary to achieve complete coverage of the surveyed objects due to occlusion and large object size. Therefore, in order to reconstruct three-dimensional models of the objects, the task of registration is required to transform several individual scans into a common reference frame. This thesis introduces three alternative approaches for the coarse registration of two adjacent scans, namely, feature-based approach, pseudo-conjugate point-based method, and closed-form solution. In the feature-based approach, linear and planar features in the overlapping area of adjacent scans are selected as registration primitives. The pseudo-conjugate point-based method utilizes non-corresponding points along common linear and planar features to estimate transformation parameters. The pseudo-conjugate point-based method is simpler than the feature-based approach since the partial derivatives are easier to compute. In the closed-form solution, a rotation matrix is first estimated by using a unit quaternion, which is a concise description of the rotation. Afterward, the translation parameters are estimated with non-corresponding points along the linear or planar features by using the pseudo-conjugate point-based method. Alternative approaches for fitting a line or plane to data with errors in three-dimensional space are investigated.</p><p><br></p><p>Experiments are conducted using simulated and real datasets to verify the effectiveness of the introduced registration procedures and feature fitting approaches. The proposed two approaches of line fitting are tested with simulated datasets. The results suggest that these two approaches can produce identical line parameters and variance-covariance matrix. The three registration approaches are tested with both simulated and real datasets. In the simulated datasets, all three registration approaches produced equivalent transformation parameters using linear or planar features. The comparison between the simulated linear and planar features shows that both features can produce equivalent registration results. In the real datasets, the three registration approaches using the linear or planar features also produced equivalent results. In addition, the results using real data indicates that the registration approaches using planar features produced better results than the approaches using linear features. The experiments show that the pseudo-conjugate point-based approach is easier to implement than the feature-based approach. The pseudo-conjugate point-based method and feature-based approach are nonlinear, so an initial guess of transformation parameters is required in these two approaches. Compared to the nonlinear approaches, the closed-form solution is linear and hence it can achieve the registration of two adjacent scans without the requirement of any initial guess for transformation parameters. Therefore, the pseudo-conjugate point-based method and closed-form solution are the preferred approaches for coarse registration using linear or planar features. In real practice, the planar features would have a better preference when compared to linear features since the linear features are derived indirectly by the intersection of neighboring planar features. To get enough lines with different orientations, planes that are far apart from each other have to be extrapolated to derive lines.</p><div><br></div>
7

Multiple Outlier Detection: Hypothesis Tests versus Model Selection by Information Criteria

Lehmann, Rüdiger, Lösler, Michael 14 June 2017 (has links) (PDF)
The detection of multiple outliers can be interpreted as a model selection problem. Models that can be selected are the null model, which indicates an outlier free set of observations, or a class of alternative models, which contain a set of additional bias parameters. A common way to select the right model is by using a statistical hypothesis test. In geodesy data snooping is most popular. Another approach arises from information theory. Here, the Akaike information criterion (AIC) is used to select an appropriate model for a given set of observations. The AIC is based on the Kullback-Leibler divergence, which describes the discrepancy between the model candidates. Both approaches are discussed and applied to test problems: the fitting of a straight line and a geodetic network. Some relationships between data snooping and information criteria are discussed. When compared, it turns out that the information criteria approach is more simple and elegant. Along with AIC there are many alternative information criteria for selecting different outliers, and it is not clear which one is optimal.
8

Multiple Outlier Detection: Hypothesis Tests versus Model Selection by Information Criteria

Lehmann, Rüdiger, Lösler, Michael January 2016 (has links)
The detection of multiple outliers can be interpreted as a model selection problem. Models that can be selected are the null model, which indicates an outlier free set of observations, or a class of alternative models, which contain a set of additional bias parameters. A common way to select the right model is by using a statistical hypothesis test. In geodesy data snooping is most popular. Another approach arises from information theory. Here, the Akaike information criterion (AIC) is used to select an appropriate model for a given set of observations. The AIC is based on the Kullback-Leibler divergence, which describes the discrepancy between the model candidates. Both approaches are discussed and applied to test problems: the fitting of a straight line and a geodetic network. Some relationships between data snooping and information criteria are discussed. When compared, it turns out that the information criteria approach is more simple and elegant. Along with AIC there are many alternative information criteria for selecting different outliers, and it is not clear which one is optimal.
9

Site-Specific Point Positioning and GPS Code Multipath Parameterization and Prediction

EDWARDS, KARLA ROBERTA LISA 25 October 2011 (has links)
No description available.

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