Universität Stuttgart
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Item Open Access Towards improved targetless registration and deformation analysis of TLS point clouds using patch-based segmentation(2023) Yang, Yihui; Schwieger, Volker (Prof. Dr.-Ing. habil. Dr. h.c.)The geometric changes in the real world can be captured by measuring and comparing the 3D coordinates of object surfaces. Traditional point-wise measurements with low spatial resolution may fail to detect inhomogeneous, anisotropic and unexpected deformations, and thus cannot reveal complex deformation processes. 3D point clouds generated from laser scanning or photogrammetric techniques have opened up opportunities for an area-wise acquisition of spatial information. In particular, terrestrial laser scanning (TLS) exhibits rapid development and wide application in areal geodetic monitoring owing to the high resolution and high quality of acquired point cloud data. However, several issues in the process chain of TLS-based deformation monitoring are still not solved satisfactorily. This thesis mainly focuses on the targetless registration and deformation analysis of TLS point clouds, aiming to develop novel data-driven methods to tackle the current challenges. For most deformation processes of natural scenes, in some local areas no shape deformations occur (i.e., these areas are rigid), and even the deformation directions show a certain level of consistency when these areas are small enough. Further point cloud processing, like stability and deformation analyses, could benefit from the assumptions of local rigidity and consistency of deformed point clouds. In this thesis, thereby, three typical types of locally rigid patches - small planar patches, geometric primitives, and quasi-rigid areas - can be generated from 3D point clouds by specific segmentation techniques. These patches, on the one hand, can preserve the boundaries between rigid and non-rigid areas and thus enable spatial separation with respect to surface stability. On the other hand, local geometric information and empirical stochastic models could be readily determined by the points in each patch. Based on these segmented rigid patches, targetless registration and deformation analysis of deformed TLS point clouds can be improved regarding accuracy and spatial resolution. Specifically, small planar patches like supervoxels are utilized to distinguish the stable and unstable areas in an iterative registration process, thus ensuring only relatively stable points are involved in estimating transformation parameters. The experimental results show that the proposed targetless registration method has significantly improved the registration accuracy. These small planar patches are also exploited to develop a novel variant of the multiscale model-to-model cloud comparison (M3C2) algorithm, which constructs prisms extending from planar patches instead of the cylinders in standard M3C2. This new method separates actual surface variations and measurement uncertainties, thus yielding lower-uncertainty and higher-resolution deformations. A coarse-to-fine segmentation framework is used to extract multiple geometric primitives from point clouds, and rigorous parameter estimations are performed individually to derive high-precision parametric deformations. Besides, a generalized local registration-based pipeline is proposed to derive dense displacement vectors based on segmented quasi-rigid areas that are corresponded by areal geometric feature descriptors. All proposed methods are successfully verified and evaluated by simulated and/or real point cloud data. The choice of proposed deformation analysis methods for specific scenarios or applications is also provided in this thesis.Item Open Access Data processing, analysis, and evaluation methods for co-design of coreless filament-wound building systems(2023) Gil Pérez, Marta; Mindermann, Pascal; Zechmeister, Christoph; Forster, David; Guo, Yanan; Hügle, Sebastian; Kannenberg, Fabian; Balangé, Laura; Schwieger, Volker; Middendorf, Peter; Bischoff, Manfred; Menges, Achim; Gresser, Götz T.; Knippers, JanItem Open Access Use of non-linearity as a characteristic in the selection of filtering algorithms in kinematic positioning(2020) Pham, Dung; Schwieger, Volker (Prof. Dr.-Ing. habil. Dr. h.c.)Selection of an optimal filtering algorithm for kinematic positioning systems constitutes one of the most extensively studied applications in the surveyor engineering community. The ability of a filtering algorithm is often assessed through its performance. The performance of a filtering algorithm is frequently evaluated in terms of accuracy and computational time. According to the accuracy parameter, it is often determined by a comparison between true trajectory and the estimated one from an algorithm. However, the true trajectory is commonly unknown in real-life situations, and thus the accuracy of the filtering algorithm cannot be assessed in this manner. Indeed, lack of true trajectory is one of the primary obstacles in the evaluation of the performance of filtering algorithms. The non-linearity of the model, on the other hand, can be determined without any information about the true trajectory and is also associated with the abilities of algorithms. So far, however, very little attention has been paid to the role of the decision of filtering algorithms based on non-linearity. Thus, this study proposes an alternative characteristic in the assessment of the performance of filtering algorithms, which is the non-linearity of the observation model. This research aims to assess the ability of non-linear characteristic for the choice of an optimal filtering algorithm. In this research, the data are simulated by the Monte Carlo method. The abilities of filtering algorithms are investigated on the extended Kalman filter (EKF), unscented Kalman filter (UKF), and particle filter (PF). These algorithms are widely utilized in kinematic positioning, and they are appropriate for various levels of non-linearity. The current study evaluated the influence of the algorithm’s accuracy on three factors: measurement uncertainty, observation geometry, and the number of observations. These algorithms are also assessed on their computational times according to a certain scenario. Regarding measures of non-linearity, three different indicators are examined for the non-linearity of both system and observation models. The coefficient of determination, 1-R2, is utilized as a single indicator to measure the non-linearity of each function of the above models. The M and 1-MVA, known as the deviation of a non-linear function from linearity and multivariate association, respectively, can be used as indicators to quantify the non-linearity of numerous functions of the above models jointly. The 1-MVA indicator is proposed for the first time to quantify the non-linearity of models. From analyses of the accuracy and non-linearity, the relationship between them is determined with changing measurement uncertainty and observation geometry in several scenarios. Based on the established relationship between accuracy and non-linearity, the choice of an optimal algorithm is analyzed through numerical examples. These results indicate that the accuracy of these algorithms is strongly influenced by measurement uncertainty, observation geometry, and the number of observations. The accuracy obtained by PF is higher than that of UKF and EKF. Conversely, the computational time of EKF is shorter than that of UKF and PF. According to measures of non-linearity, the above-proposed indicators are suitable, and the tendency of non-linearity of a model obtained by these indicators is the same. The non-linearity of the system model is small due to the given small amount of standard deviations of the disturbance quantities. Inversely, the non-linearity of the observation model is high due to high measurement uncertainties, or poor observation geometries. The main finding of this research is that both non-linearity of the observation model and position accuracy are influenced by factors of measurement uncertainty and observation geometry. Therefore, the relationship between the position accuracy and the non-linearity of the observation model is established based on these factors. This relationship is strong, which is assessed by the goodness-of-fit value of the best fitting function. In addition, another important result from the present research is that the fitting function described for this relationship changes due to influencing factors of scenarios. The established relationship constitutes the main limitation of this characteristic in application. As a result, instead of accuracy, the non-linearity of the observation model can be employed for the assessment of algorithms when the true trajectory is not available. However, the optimal algorithm can only be selected using these factors in some special cases. For a general case of arbitrary scenarios’ factors, the non-linear characteristic cannot be used for this purpose.Item Open Access Untersuchungen zum geometrischen Verhalten von Holz mittels optischer Sensoren(2024) Schmitt, Annette; Schwieger, Volker (Prof. Dr.-Ing. habil. Dr. h.c.)In Deutschland geht rund ein Drittel des jährlichen CO2-Ausstoßes auf dem Bausektor zurück. Davon ist zwar nur ein Viertel dem Bau von Hochbauten zu zuschreiben. Gerade deshalb müssen im Hochbau Innovationen und alternative Materialien und Bauweisen entwickelt werden, damit Deutschland seine Klimaziele erreicht. Neben dem hohen CO2-Ausstoß hat die Betonbauweise den Nachteil, dass die Rohstoffe von Beton wie zum Beispiel Kies, Sand oder Kalkstein, endliche Ressourcen sind. Eine Alternative zur Betonbauweise ist der jahrtausendealte Holzbau, der in letzten Jahren eine Renaissance erlebt hat. Durch einen nachhaltigen Holzanbau und eine nachhaltige, ressourcenschonende Bauweise kann Holzbau zu einer echten Alternative werden. Jedoch ist Holz ein anisotroper, inhomogener und poröser Werkstoff, dessen Eigenschaften stark richtungsabhängig und abhängig von Umwelteinflüssen sind. Dies macht die Bemessung von Holzbauwerken kompliziert und unattraktiv. Speziell bei Flächentragwerken wie Schalen, die in der Regel sehr filigran sind, haben Umwelteinflüsse wie Feuchte und Temperatur einen Einfluss auf die Standfestigkeit. Daher ist eine regelmäßige Überwachung der Struktur notwendig. Im Bauingenieurwesen werden für solche Aufgaben häufig Dehnmessstreifen eingesetzt. Diese liefern lediglich sehr lokal geltende Messwerte, von denen nur mittels mechanischer Modelle auf das gesamte Objekt geschlossen werden kann. Daher bietet es sich an, für Flächentragwerke optische Sensoren wie zum Beispiel Laserscanner einzusetzen. Im Rahmen dieser Arbeit werden verschiedene Holzobjekte, wie zum Beispiel Platten, Vierkanthölzer und Schalen, unter verschiedenen Umwelteinflüssen, wie Feuchte und Temperatur, untersucht. Ziel ist es dabei, die auftretenden Formänderungen durch Umwelteinflüsse mittels Laserscanner und Lasertracker zu detektieren. Unter anderem werden mehrere Holzplatten in Klimakammern unter definierten Bedingungen untersucht. So wird in einem ersten Versuch der Einfluss von Temperaturänderungen auf eine Holzplatte untersucht. Es zeigt sich, dass dieser zwar sehr gering ist, aber mittels Lasertracker zumindest in radialer Faserrichtung signifikant aufdeckbar ist. In einem weiteren Versuch werden Holzplatten zunächst in einer Klimakammer mit Feuchteregelung bei 95 % Luftfeuchte gelagert und anschließend bei 12 % Luftfeuchte getrocknet. Zwischenzeitlich werden die Platten mittels Lasertracker und Laserscanner vermessen. Hier lassen sich die Verformungen mit dem Lasertracker in allen drei Faserrichtungen signifikant detektieren. Die Messungen mit dem Laserscanner ermöglichen aufgrund des aus der Aufnahmekonfiguration folgenden Registrierungsfehlers keine Aufdeckung der Verformungen, da der Schwellwert für signifikante Verformungen zu hoch ist. In einem weiteren Laborversuch werden die Verformungen durch die Umwelteinflüsse auf belastete Vierkanthölzer untersucht. Auch hierfür kann gezeigt werden, dass der Lasertracker genutzt werden kann. Verifiziert wurden die Ergebnisse hierbei durch eine Finite-Elemente-Simulation, der Materialparameter aus der Literatur zugrunde liegen. Neben den Laborversuchen werden auch Untersuchungen an einem adaptiven Schalentragwerk aus Holz mit dem Laserscanner durchgeführt. Für die Auswertung der Laserscannerdaten wird eine Methode zur Detektion von signifikanten Formänderungen auf Basis von synthetischen Punktfehlern und der Deformationsanalyse implementiert. Alle Ergebnisse der Messungen sind plausibel und mit Literaturangaben vergleichbar, dennoch ist Holz als natürlich wachsender Rohstoff sehr anspruchsvoll und individuell.Item Open Access Monitoring of the production process of graded concrete component using terrestrial laser scanning(2021) Yang, Yihui; Balangé, Laura; Gericke, Oliver; Schmeer, Daniel; Zhang, Li; Sobek, Werner; Schwieger, VolkerItem Open Access Entwicklung eines tachymeter-basierten Zielsystems(2023) Hassan, Aiham; Schwieger, Volker (Prof. Dr.-Ing. habil. Dr. h.c.)Im Rahmen dieser Arbeit wird ein Prototyp für ein flexibel einsetzbares Tachymeterzielsystem (TZS) zur Vermessung verdeckter Objektpunkte entwickelt und empirisch anhand von Testmessungen untersucht. Die Ergebnisse dieser Untersuchungen zeigen, dass das Potenzial des TZS vielversprechend ist. Des Weiteren wird die Methode der lokalen Sensitivitätsanalyse zur Identifikation der wichtigen Eingangsgrößen für das deterministische Modell des TZS eingesetzt. Anhand der Ergebnisse dieser Analyse wird eine Optimierung dieses Modells durchgeführt.Item Open Access Holistic quality model and assessment : supporting decision-making towards sustainable construction using the design and production of graded concrete components as an example(2022) Frost, Deniz; Gericke, Oliver; Di Bari, Roberta; Balangé, Laura; Zhang, Li; Blagojevic, Boris; Nigl, David; Haag, Phillip; Blandini, Lucio; Jünger, Hans Christian; Kropp, Cordula; Leistner, Philip; Sawodny, Oliver; Schwieger, Volker; Sobek, WernerThis paper describes a holistic quality model (HQM) and assessment to support decision-making processes in construction. A graded concrete slab serves as an example to illustrate how to consider technical, environmental, and social quality criteria and their interrelations. The evaluation of the design and production process of the graded concrete component shows that it has advantages compared to a conventional solid slab, especially in terms of environmental performance. At the same time, the holistic quality model identifies potential improvements for the technology of graded concrete. It will be shown that the holistic quality model can be used to (a) consider the whole life cycle in decision-making in the early phases and, thus, make the complexity of construction processes manageable for quality and sustainability assessments and (b) make visible interdependencies between different quality and sustainability criteria, to help designers make better-informed decisions regarding the overall quality. The results show how different quality aspects can be assessed and trade-offs are also possible through the understanding of the relationships among characteristics. For this purpose, in addition to the quality assessment of graded concrete, an overview of the interrelations of different quality characteristics is provided. While this article demonstrates how a HQM can support decision-making in design, the validity of the presented evaluation is limited by the data availability and methodological challenges, specifically regarding the quantification of interrelations.Item Open Access Entwicklung eines Steuerungssystems für eine Laderaupe zur Durchführung vollautomatisierter Ladeprozesse unter Einsatz bildverarbeitender Robottachymeter und adaptiver Regelung(2020) Lerke, Otto; Schwieger, Volker (Prof. Dr.-Ing. habil.)Die Automatisierung von Bauprozessen spielt eine immer wichtigere Rolle auf Baustellen. Automatisierung ermöglicht es, Arbeiten in kürzerer Zeit durchzuführen und gleichzeitig eine Erhöhung der Arbeitsqualität zu erreichen. Daneben kann auch die Arbeitssicherheit gesteigert werden. Der Baubetrieb ist im Allgemeinen in mannigfaltige und vielschichtige Prozesse unterteilt. Viele Prozesse werden von automatisierten Baumaschinen durchgeführt. Für den Bereich Erdbewegungen werden Rad- oder Raupenfahrzeuge mit entsprechenden Ladewerkzeugen eingesetzt, die jedoch zum jetzigen Zeitpunkt nicht automatisiert sind. Ziel dieser Arbeit ist es, ein System zu entwickeln, welches es ermöglicht, Belade- und Entladevorgänge vollautomatisch durchzuführen. Dies dient dazu, das Spektrum erhältlicher Systeme bei Erdbewegungsmaschinen, um semi-automatische und vollautomatische 3D Systeme zu erweitern. Die Funktionsweise des Systems wird anhand eines Laderaupenmodells im Massstab 1:14 demonstriert. Die Innovationen sind die bildbasierte Positionsbestimmung mit bildverarbeitenden Tachymetern und die Konzeption einer adaptiven Regelung zur automatischen Führung von Raupenfahrzeugen.Item Open Access Application of Copernicus data for climate-relevant urban planning using the example of water, heat, and vegetation(2021) Bühler, Michael Max; Sebald, Christoph; Rechid, Diana; Baier, Eberhard; Michalski, Alexander; Rothstein, Benno; Nübel, Konrad; Metzner, Martin; Schwieger, Volker; Harrs, Jan-Albrecht; Jacob, Daniela; Köhler, Lothar; In het Panhuis, Gunnar; Rodríguez Tejeda, Raymundo C.; Herrmann, Michael; Buziek, GerdSpecific climate adaptation and resilience measures can be efficiently designed and implemented at regional and local levels. Climate and environmental databases are critical for achieving the sustainable development goals (SDGs) and for efficiently planning and implementing appropriate adaptation measures. Available federated and distributed databases can serve as necessary starting points for municipalities to identify needs, prioritize resources, and allocate investments, taking into account often tight budget constraints. High-quality geospatial, climate, and environmental data are now broadly available and remote sensing data, e.g., Copernicus services, will be critical. There are forward-looking approaches to use these datasets to derive forecasts for optimizing urban planning processes for local governments. On the municipal level, however, the existing data have only been used to a limited extent. There are no adequate tools for urban planning with which remote sensing data can be merged and meaningfully combined with local data and further processed and applied in municipal planning and decision-making. Therefore, our project CoKLIMAx aims at the development of new digital products, advanced urban services, and procedures, such as the development of practical technical tools that capture different remote sensing and in-situ data sets for validation and further processing. CoKLIMAx will be used to develop a scalable toolbox for urban planning to increase climate resilience. Focus areas of the project will be water (e.g., soil sealing, stormwater drainage, retention, and flood protection), urban (micro)climate (e.g., heat islands and air flows), and vegetation (e.g., greening strategy, vegetation monitoring/vitality). To this end, new digital process structures will be embedded in local government to enable better policy decisions for the future.Item Open Access Method of development of a new regional ionosphere model (RIM) to improve static single-frequency precise point positioning (SF-PPP) for Egypt using Bernese GNSS software(2023) Abdallah, Ashraf; Agag, Tarek; Schwieger, VolkerDue to the lack of coverage of IGS in Africa, especially over North Africa, and the construction revolution of infrastructure in Egypt, a geodetic CORS stations network was established in 2012. These CORS stations are operated by the Egyptian Surveying Authority (Egy. SA) and cover the whole of Egypt. The paper presents a fully developed regional ionosphere model (RIM) depending on the Egyptian CORS stations. The new model and the PPP solution were obtained using Bernese GNSS V. 5.2 software. An observation data series of eight days (DOY 201-208)/2019 was used in this study. Eighteen stations were used to develop the RIM model for each day; fifteen stations were used to validate the new RIM model. A static SF-PPP solution was obtained using the CODE-GIM and RIM models. Comparing the outcomes to the reference network solution, based on the recently developed RIM model, the solution showed a mean error of 0.06 m in the East direction, 0.13 m in the North direction, and 0.21 m in the height direction. In the East, North, and height directions, this solution improves the SF-PPP result achieved by the Global Ionosphere Maps (CODE-GIM) model by 60%, 68%, and 77%, respectively.