Spelling suggestions: "subject:"point detection"" "subject:"joint detection""
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Deep Learning for Point Detection in ImagesRunow, Björn January 2020 (has links)
The main result of this thesis is a deep learning model named BearNet, which can be trained to detect an arbitrary amount of objects as a set of points. The model is trained using the Weighted Hausdorff distance as loss function. BearNet has been applied and tested on two problems from the industry. These are: From an intensity image, detect two pocket points of an EU-pallet which an autonomous forklift could utilize when determining where to insert its forks. From a depth image, detect the start, bend and end points of a straw attached to a juice package, in order to help determine if the straw has been attached correctly. In the development process of BearNet I took inspiration from the designs of U-Net, UNet++ and a high resolution network named HRNet. Further, I used a dataset containing RGB-images from a surveillance camera located inside a mall, on which the aim was to detect head positions of all pedestrians. In an attempt to reproduce a result from another study, I found that the mall dataset suffers from training set contamination when a model is trained, validated, and tested on it with random sampling. Hence, I propose that the mall dataset is evaluated with a sequential data split strategy, to limit the problem. I found that the BearNet architecture is well suited for both the EU-pallet and straw datasets, and that it can be successfully used on either RGB, intensity or depth images. On the EU-pallet and straw datasets, BearNet consistently produces point estimates within five and six pixels of ground truth, respectively. I also show that the straw dataset only constitutes a small subset of all the challenges that exist in the problem domain related to the attachment of a straw to a juice package, and that one therefore cannot train a robust deep learning model on it. As an example of this, models trained on the straw dataset cannot correctly handle samples in which there is no straw visible.
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Detekce význačných bodů v obraze / Interest Point Detection in ImagesDuda, Tomáš Unknown Date (has links)
This master's thesis deals with the interest point detection in images. The main goal is to create an application for making panoramic photos, which is based on this detection. The application uses the SIFT detector for finding keypoints of the image. Afterwards the geometrical consistence of image points using the RANSAC algorithm is finds out and images are transform into panorama in accordance with this geometrical consistence. Finally techniques for blending of transition between photos are used.
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Parametrizace bodů a čar pomocí paralelních souřadnic pro Houghovu transformaci / Point and Line Parameterizations Using Parallel Coordinates for Hough TransformJuránková, Markéta Unknown Date (has links)
Tato dizertační práce se zaměřuje na použití paralelních souřadnic pro parametrizaci čar a bodů. Paralelní souřadný systém má souřadnicové osy vzájemně rovnoběžné. Bod ve dvourozměrném prostoru je v paralelních souřadnicích zobrazen jako přímka a přímka jako bod. Toho je možné využít pro Houghovu transformaci - metodu, při které body zájmu hlasují v prostoru parametrů pro danou hypotézu. Parametrizace pomocí paralelních souřadnic vyžaduje pouze rasterizaci úseček, a proto je velmi rychlá a přesná. V práci je tato parameterizace demonstrována na detekci maticových kódů a úběžníků.
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Regression discontinuity design with unknown cutoff: cutoff detection & effect estimationKhan Tanu, Tanvir Ahmed 27 August 2020 (has links)
Regression discontinuity designs are increasingly popular quasi-experimental research designs among applied econometricians desiring to make causal inferences on the local effect of a treatment, intervention, or policy. They are also widely used in social, behavioral, and natural sciences. Much of the existing literature relies on the assumption that the discontinuity point or cutoff is known a-priori, which may not always hold. This thesis seeks to extend the applicability of regression discontinuity designs by proposing a new approach towards detection of an unknown discontinuity point using structural-break detection and machine learning methods. The approach is evaluated on both simulated and real data. Estimation and inference based on estimating the cutoff following this approach are compared to the counterfactual scenario where the cutoff is known. Monte Carlo simulations show that the empirical false-detection and true-detection probabilities of the proposed procedure are generally satisfactory. Finally, the approach is further illustrated with an empirical application. / Graduate
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Evaluace metod vyhledávání klíčových bodů / Evaluation of Key Point Detection MethodsKordula, Jaroslav January 2007 (has links)
The goal of this thesis is to get familiarized with software component Microsoft .NET Framework and the problems of methods of interest point detection. On the basis of this knowledge, it is required to develop a method for the evaluation of used detectors and then implement a console application that is simply able to evaluate the results of interest point detection methods. Such evaluation is important in the process of development of the algorithms for the detection using projected method of evaluation. The interest points are searched in several images which represent the same scene from different angles of view. The requirements also inculde creation of graphic user interface that allows an easy way to setup the evaluation conditions.
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Statistical Inference for Change Points in High-Dimensional Offline and Online DataLi, Lingjun 07 April 2020 (has links)
No description available.
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Improving Change Point Detection Using Self-Supervised VAEs : A Study on Distance Metrics and Hyperparameters in Time Series AnalysisWorkinn, Daniel January 2023 (has links)
This thesis addresses the optimization of the Variational Autoencoder-based Change Point Detection (VAE-CP) approach in time series analysis, a vital component in data-driven decision making. We evaluate the impact of various distance metrics and hyperparameters on the model’s performance using a systematic exploration and robustness testing on diverse real-world datasets. Findings show that the Dynamic Time Warping (DTW) distance metric significantly enhances the quality of the extracted latent variable space and improves change point detection. The research underscores the potential of the VAE-CP approach for more effective and robust handling of complex time series data, advancing the capabilities of change point detection techniques. / Denna uppsats behandlar optimeringen av en Variational Autoencoder-baserad Change Point Detection (VAE-CP)-metod i tidsserieanalys, en vital komponent i datadrivet beslutsfattande. Vi utvärderar inverkan av olika distansmått och hyperparametrar på modellens prestanda med hjälp av systematisk utforskning och robusthetstestning på diverse verkliga datamängder. Resultaten visar att distansmåttet Dynamic Time Warping (DTW) betydligt förbättrar kvaliteten på det extraherade latenta variabelutrymmet och förbättrar detektionen av brytpunkter (eng. change points). Forskningen understryker potentialen med VAE-CP-metoden för mer effektiv och robust hantering av komplexa tidsseriedata, vilket förbättrar förmågan hos tekniker för att upptäcka brytpunkter.
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An empirical study of the impact of data dimensionality on the performance of change point detection algorithms / En empirisk studie av data dimensionalitetens påverkan på change point detection algoritmers prestandaNoharet, Léo January 2023 (has links)
When a system is monitored over time, changes can be discovered in the time series of monitored variables. Change Point Detection (CPD) aims at finding the time point where a change occurs in the monitored system. While CPD methods date back to the 1950’s with applications in quality control, few studies have been conducted on the impact of data dimensionality on CPD algorithms. This thesis intends to address this gap by examining five different algorithms using synthetic data that incorporates changes in mean, covariance, and frequency across dimensionalities up to 100. Additionally, the algorithms are evaluated on a collection of data sets originating from various domains. The studied methods are then assessed and ranked based on their performance on both synthetic and real data sets, to aid future users in selecting an appropriate CPD method. Finally, stock data from the 30 most traded companies on the Swedish stock market are collected to create a new CPD data set to which the CPD algorithms are applied. The changes of the monitored system that the CPD algorithms aim to detect are the changes in policy rate set by the Swedish central bank, Riksbank. The results of the thesis show that the dimensionality impacts the accuracy of the methods when noise is present and when the degree of mean or covariance change is small. Additionally, the application of the algorithms on real world data sets reveals large differences in performance between the studied methods, underlining the importance of comparison studies. Ultimately, the kernel based CPD method performed the best across the real world data set employed in the thesis. / När system övervakas över tid kan förändringar upptäckas i de uppmätade variablers tidsseriedata. Change Point Detection (CPD) syftar till att hitta tidpunkten då en förändring inträffar i det övervakade systemet’s tidseriedata. Medan CPD-metoder har sitt urspring i kvalitetskontroll under 1950-talet, har få studier undersökt datans dimensionalitets påverkan på CPD-algoritmer’s förmåga. Denna avhandling avser att fylla denna kunskapslucka genom att undersöka fem olika algoritmer med hjälp av syntetiska data som inkorporerar förändringar i medelvärde, kovarians och frekvens över dimensioner upp till 100. Dessutom jämförs algoritmerna med hjälp av en samling av data från olika domäner. De studerade metoderna bedöms och rangordnas sedan baserat på deras prestanda på både syntetiska och verkliga datauppsättningar för att hjälpa framtida användare att välja en lämplig CPD algoritm. Slutligen har aktiedata samlats från de 30 mest handlade företagen på den svenska aktiemarknaden för att skapa ett nytt data set. De förändringar i det övervakade systemet som CPD-algoritmerna syftar till att upptäcka är förändringarna i styrräntan som fastställs av Riksbanken. Resultaten av studien tyder på att dimensionaliteten påverkar förmågan hos algoritmerna att upptäcka förändringspunkterna när brus förekommer i datan och när graden av förändringen är liten. Dessutom avslöjar tillämpningen av algoritmerna på den verkliga datan stora skillnader i prestanda mellan de studerade metoderna, vilket understryker vikten av jämförelsestudier för att avslöja dessa skillnader. Slutligen presterade den kernel baserade CPD metoden bäst.
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A window to the past through modern urban environments: Developing a photogrammetric workflow for the orientation parameter estimation of historical imagesMaiwald, Ferdinand 05 October 2022 (has links)
The ongoing process of digitization in archives is providing access to ever-increasing historical image collections. In many of these repositories, images can typically be viewed in a list or gallery view. Due to the growing number of digitized objects, this type of visualization is becoming increasingly complex. Among other things, it is difficult to determine how many photographs show a particular object and spatial information can only be communicated via metadata.
Within the scope of this thesis, research is conducted on the automated determination and provision of this spatial data. Enhanced visualization options make this information more eas- ily accessible to scientists as well as citizens. Different types of visualizations can be presented in three-dimensional (3D), Virtual Reality (VR) or Augmented Reality (AR) applications. However, applications of this type require the estimation of the photographer’s point of view. In the photogrammetric context, this is referred to as estimating the interior and exterior orientation parameters of the camera. For determination of orientation parameters for single images, there are the established methods of Direct Linear Transformation (DLT) or photogrammetric space resection. Using these methods requires the assignment of measured object points to their homologue image points. This is feasible for single images, but quickly becomes impractical due to the large amount of images available in archives. Thus, for larger image collections, usually the Structure-from-Motion (SfM) method is chosen, which allows the simultaneous estimation of the interior as well as the exterior orientation of the cameras. While this method yields good results especially for sequential, contemporary image data, its application to unsorted historical photographs poses a major challenge.
In the context of this work, which is mainly limited to scenarios of urban terrestrial photographs, the reasons for failure of the SfM process are identified. In contrast to sequential image collections, pairs of images from different points in time or from varying viewpoints show huge differences in terms of scene representation such as deviations in the lighting situation, building state, or seasonal changes. Since homologue image points have to be found automatically in image pairs or image sequences in the feature matching procedure of SfM, these image differences
pose the most complex problem.
In order to test different feature matching methods, it is necessary to use a pre-oriented historical dataset. Since such a benchmark dataset did not exist yet, eight historical image triples (corresponding to 24 image pairs) are oriented in this work by manual selection of homologue image points. This dataset allows the evaluation of frequently new published methods in feature matching. The initial methods used, which are based on algorithmic procedures for feature matching (e.g., Scale Invariant Feature Transform (SIFT)), provide satisfactory results for only few of the image pairs in this dataset. By introducing methods that use neural networks for feature detection and feature description, homologue features can be reliably found for a large fraction of image pairs in the benchmark dataset.
In addition to a successful feature matching strategy, determining camera orientation requires an initial estimate of the principal distance. Hence for historical images, the principal distance cannot be directly determined as the camera information is usually lost during the process of digitizing the analog original. A possible solution to this problem is to use three vanishing points that are automatically detected in the historical image and from which the principal distance can then be determined. The combination of principal distance estimation and robust feature matching is integrated into the SfM process and allows the determination of the interior
and exterior camera orientation parameters of historical images. Based on
these results, a workflow is designed that allows archives to be directly connected to 3D applications.
A search query in archives is usually performed using keywords, which have to be assigned to the corresponding object as metadata. Therefore, a keyword search for a specific building also results in hits on drawings, paintings, events, interior or detailed views directly connected to this building. However, for the successful application of SfM in an urban context, primarily the photographic exterior view of the building is of interest. While the images for a single building can be sorted by hand, this process is too time-consuming for multiple buildings.
Therefore, in collaboration with the Competence Center for Scalable Data Services and Solutions (ScaDS), an approach is developed to filter historical photographs by image similarities. This method reliably enables the search for content-similar views via the selection of one or more query images. By linking this content-based image retrieval with the SfM approach, automatic determination of camera parameters for a large number of historical photographs is possible. The developed method represents a significant improvement over commercial and open-source SfM standard solutions.
The result of this work is a complete workflow from archive to application that automatically filters images and calculates the camera parameters. The expected accuracy of a few meters for the camera position is sufficient for the presented applications in this work, but offer further potential for improvement. A connection to archives, which will automatically exchange photographs and positions via interfaces, is currently under development. This makes it possible to retrieve interior and exterior orientation parameters directly from historical photography as metadata which opens up new fields of research.:1 Introduction 1
1.1 Thesis structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Historical image data and archives . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Structure-from-Motion for historical images . . . . . . . . . . . . . . . . . . . 4
1.3.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3.2 Selection of images and preprocessing . . . . . . . . . . . . . . . . . . 5
1.3.3 Feature detection, feature description and feature matching . . . . . . 6
1.3.3.1 Feature detection . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3.3.2 Feature description . . . . . . . . . . . . . . . . . . . . . . . 9
1.3.3.3 Feature matching . . . . . . . . . . . . . . . . . . . . . . . . 10
1.3.3.4 Geometric verification and robust estimators . . . . . . . . . 13
1.3.3.5 Joint methods . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.3.4 Initial parameterization . . . . . . . . . . . . . . . . . . . . . . . . . . 19
1.3.5 Bundle adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
1.3.6 Dense reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
1.3.7 Georeferencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
1.4 Research objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2 Generation of a benchmark dataset using historical photographs for the evaluation
of feature matching methods 29
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.1.1 Image differences based on digitization and image medium . . . . . . . 30
2.1.2 Image differences based on different cameras and acquisition technique 31
2.1.3 Object differences based on different dates of acquisition . . . . . . . . 31
2.2 Related work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.3 The image dataset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.4 Comparison of different feature detection and description methods . . . . . . 35
2.4.1 Oriented FAST and Rotated BRIEF (ORB) . . . . . . . . . . . . . . . 36
2.4.2 Maximally Stable Extremal Region Detector (MSER) . . . . . . . . . 36
2.4.3 Radiation-invariant Feature Transform (RIFT) . . . . . . . . . . . . . 36
2.4.4 Feature matching and outlier removal . . . . . . . . . . . . . . . . . . 36
2.5 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.6 Conclusions and future work . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3 Photogrammetry as a link between image repository and 4D applications 45
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
IX
Contents
3.2 Multimodal access on repositories . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.2.1 Conventional access . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.2.2 Virtual access using online collections . . . . . . . . . . . . . . . . . . 48
3.2.3 Virtual museums . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
3.3 Workflow and access strategies . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.3.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.3.2 Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.3.3 Photogrammetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.3.4 Browser access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
3.3.5 VR and AR access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
3.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4 An adapted Structure-from-Motion Workflow for the orientation of historical
images 69
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.2 Related Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.2.1 Historical images for 3D reconstruction . . . . . . . . . . . . . . . . . 72
4.2.2 Algorithmic Feature Detection and Matching . . . . . . . . . . . . . . 73
4.2.3 Feature Detection and Matching using Convolutional Neural Networks 74
4.3 Feature Matching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
4.4 Workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
4.4.1 Step 1: Data preparation . . . . . . . . . . . . . . . . . . . . . . . . . 78
4.4.2 Step 2.1: Feature Detection and Matching . . . . . . . . . . . . . . . . 78
4.4.3 Step 2.2: Vanishing Point Detection and Principal Distance Estimation 80
4.4.4 Step 3: Scene Reconstruction . . . . . . . . . . . . . . . . . . . . . . . 80
4.4.5 Comparison with Three Other State-of-the-Art SfM Workflows . . . . 81
4.5 Datasets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
4.6 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
4.7 Conclusions and Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
4.8 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
4.A Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
5 Fully automated pose estimation of historical images 97
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
5.2 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
5.2.1 Image Retrieval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
5.2.2 Feature Detection and Matching . . . . . . . . . . . . . . . . . . . . . 101
5.3 Data Preparation: Image Retrieval . . . . . . . . . . . . . . . . . . . . . . . . 102
5.3.1 Experiment and Data . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
5.3.2 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
5.3.2.1 Layer Extraction Approach (LEA) . . . . . . . . . . . . . . . 104
5.3.2.2 Attentive Deep Local Features (DELF) Approach . . . . . . 105
5.3.3 Results and Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 106
5.4 Camera Pose Estimation of Historical Images Using Photogrammetric Methods 110
5.4.1 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
5.4.1.1 Benchmark Datasets . . . . . . . . . . . . . . . . . . . . . . . 111
5.4.1.2 Retrieval Datasets . . . . . . . . . . . . . . . . . . . . . . . . 113
5.4.2 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
5.4.2.1 Feature Detection and Matching . . . . . . . . . . . . . . . . 115
5.4.2.2 Geometric Verification and Camera Pose Estimation . . . . . 116
5.4.3 Results and Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 117
5.5 Conclusions and Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
5.A Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
6 Related publications 129
6.1 Photogrammetric analysis of historical image repositores for virtual reconstruction
in the field of digital humanities . . . . . . . . . . . . . . . . . . . . . . . 130
6.2 Feature matching of historical images based on geometry of quadrilaterals . . 131
6.3 Geo-information technologies for a multimodal access on historical photographs
and maps for research and communication in urban history . . . . . . . . . . 132
6.4 An automated pipeline for a browser-based, city-scale mobile 4D VR application
based on historical images . . . . . . . . . . . . . . . . . . . . . . . . . . 133
6.5 Software and content design of a browser-based mobile 4D VR application to
explore historical city architecture . . . . . . . . . . . . . . . . . . . . . . . . 134
7 Synthesis 135
7.1 Summary of the developed workflows . . . . . . . . . . . . . . . . . . . . . . . 135
7.1.1 Error assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
7.1.2 Accuracy estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
7.1.3 Transfer of the workflow . . . . . . . . . . . . . . . . . . . . . . . . . . 141
7.2 Developments and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
8 Appendix 149
8.1 Setup for the feature matching evaluation . . . . . . . . . . . . . . . . . . . . 149
8.2 Transformation from COLMAP coordinate system to OpenGL . . . . . . . . 150
References 151
List of Figures 165
List of Tables 167
List of Abbreviations 169 / Der andauernde Prozess der Digitalisierung in Archiven ermöglicht den Zugriff auf immer größer werdende historische Bildbestände. In vielen Repositorien können die Bilder typischerweise in einer Listen- oder Gallerieansicht betrachtet werden. Aufgrund der steigenden Zahl an digitalisierten Objekten wird diese Art der Visualisierung zunehmend unübersichtlicher. Es kann u.a. nur noch schwierig bestimmt werden, wie viele Fotografien ein bestimmtes Motiv zeigen. Des Weiteren können räumliche Informationen bisher nur über Metadaten vermittelt werden.
Im Rahmen der Arbeit wird an der automatisierten Ermittlung und Bereitstellung dieser räumlichen Daten geforscht. Erweiterte Visualisierungsmöglichkeiten machen diese Informationen Wissenschaftlern sowie Bürgern einfacher zugänglich. Diese Visualisierungen können u.a. in drei-dimensionalen (3D), Virtual Reality (VR) oder Augmented Reality (AR) Anwendungen präsentiert werden. Allerdings erfordern Anwendungen dieser Art die Schätzung des Standpunktes des Fotografen. Im photogrammetrischen Kontext spricht man dabei von der Schätzung der inneren und äußeren Orientierungsparameter der Kamera. Zur Bestimmung der Orientierungsparameter für Einzelbilder existieren die etablierten Verfahren der direkten linearen Transformation oder des photogrammetrischen Rückwärtsschnittes. Dazu muss eine Zuordnung von gemessenen Objektpunkten zu ihren homologen Bildpunkten erfolgen. Das ist für einzelne Bilder realisierbar, wird aber aufgrund der großen Menge an Bildern in Archiven schnell nicht mehr praktikabel. Für größere Bildverbände wird im photogrammetrischen Kontext somit üblicherweise das Verfahren Structure-from-Motion (SfM) gewählt, das die simultane Schätzung der inneren sowie der äußeren Orientierung der Kameras ermöglicht. Während diese Methode vor allem für sequenzielle, gegenwärtige Bildverbände gute Ergebnisse liefert, stellt die Anwendung auf unsortierten historischen Fotografien eine große Herausforderung dar.
Im Rahmen der Arbeit, die sich größtenteils auf Szenarien stadträumlicher terrestrischer Fotografien beschränkt, werden zuerst die Gründe für das Scheitern des SfM Prozesses identifiziert. Im Gegensatz zu sequenziellen Bildverbänden zeigen Bildpaare aus unterschiedlichen zeitlichen Epochen oder von unterschiedlichen Standpunkten enorme Differenzen hinsichtlich der Szenendarstellung. Dies können u.a. Unterschiede in der Beleuchtungssituation, des
Aufnahmezeitpunktes oder Schäden am originalen analogen Medium sein. Da für die Merkmalszuordnung in SfM automatisiert homologe Bildpunkte in Bildpaaren bzw. Bildsequenzen gefunden werden müssen, stellen diese Bilddifferenzen die größte Schwierigkeit dar.
Um verschiedene Verfahren der Merkmalszuordnung testen zu können, ist es notwendig einen vororientierten historischen Datensatz zu verwenden. Da solch ein Benchmark-Datensatz noch nicht existierte, werden im Rahmen der Arbeit durch manuelle Selektion homologer Bildpunkte acht historische Bildtripel (entspricht 24 Bildpaaren) orientiert, die anschließend genutzt werden, um neu publizierte Verfahren bei der Merkmalszuordnung zu evaluieren. Die ersten verwendeten Methoden, die algorithmische Verfahren zur Merkmalszuordnung nutzen (z.B. Scale Invariant Feature Transform (SIFT)), liefern nur für wenige Bildpaare des Datensatzes zufriedenstellende Ergebnisse. Erst durch die Verwendung von Verfahren, die neuronale Netze zur Merkmalsdetektion und Merkmalsbeschreibung einsetzen, können für einen großen Teil der historischen Bilder des Benchmark-Datensatzes zuverlässig homologe Bildpunkte gefunden werden.
Die Bestimmung der Kameraorientierung erfordert zusätzlich zur Merkmalszuordnung eine initiale Schätzung der Kamerakonstante, die jedoch im Zuge der Digitalisierung des analogen Bildes nicht mehr direkt zu ermitteln ist. Eine mögliche Lösung dieses Problems ist die Verwendung von drei Fluchtpunkten, die automatisiert im historischen Bild detektiert werden und aus denen dann die Kamerakonstante bestimmt werden kann. Die Kombination aus Schätzung der Kamerakonstante und robuster Merkmalszuordnung wird in den SfM Prozess integriert und erlaubt die Bestimmung der Kameraorientierung historischer Bilder.
Auf Grundlage dieser Ergebnisse wird ein Arbeitsablauf konzipiert, der es ermöglicht, Archive mittels dieses photogrammetrischen Verfahrens direkt an 3D-Anwendungen anzubinden.
Eine Suchanfrage in Archiven erfolgt üblicherweise über Schlagworte, die dann als Metadaten dem entsprechenden Objekt zugeordnet sein müssen. Eine Suche nach einem bestimmten Gebäude generiert deshalb u.a. Treffer zu Zeichnungen, Gemälden, Veranstaltungen, Innen- oder Detailansichten. Für die erfolgreiche Anwendung von SfM im stadträumlichen Kontext interessiert jedoch v.a. die fotografische Außenansicht des Gebäudes. Während die Bilder für ein einzelnes Gebäude von Hand sortiert werden können, ist dieser Prozess für mehrere
Gebäude zu zeitaufwendig.
Daher wird in Zusammenarbeit mit dem Competence Center for Scalable Data Services and Solutions (ScaDS) ein Ansatz entwickelt, um historische Fotografien über Bildähnlichkeiten zu filtern. Dieser ermöglicht zuverlässig über die Auswahl eines oder mehrerer Suchbilder die Suche nach inhaltsähnlichen Ansichten. Durch die Verknüpfung der inhaltsbasierten Suche mit dem SfM Ansatz ist es möglich, automatisiert für eine große Anzahl historischer Fotografien die Kameraparameter zu bestimmen. Das entwickelte Verfahren stellt eine deutliche Verbesserung im Vergleich zu kommerziellen und open-source SfM Standardlösungen dar.
Das Ergebnis dieser Arbeit ist ein kompletter Arbeitsablauf vom Archiv bis zur Applikation, der automatisch Bilder filtert und diese orientiert. Die zu erwartende Genauigkeit von wenigen Metern für die Kameraposition sind ausreichend für die dargestellten Anwendungen in dieser Arbeit, bieten aber weiteres Verbesserungspotential. Eine Anbindung an Archive, die über Schnittstellen automatisch Fotografien und Positionen austauschen soll, befindet sich bereits in der Entwicklung. Dadurch ist es möglich, innere und äußere Orientierungsparameter direkt von der historischen Fotografie als Metadaten abzurufen, was neue Forschungsfelder eröffnet.:1 Introduction 1
1.1 Thesis structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Historical image data and archives . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Structure-from-Motion for historical images . . . . . . . . . . . . . . . . . . . 4
1.3.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3.2 Selection of images and preprocessing . . . . . . . . . . . . . . . . . . 5
1.3.3 Feature detection, feature description and feature matching . . . . . . 6
1.3.3.1 Feature detection . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3.3.2 Feature description . . . . . . . . . . . . . . . . . . . . . . . 9
1.3.3.3 Feature matching . . . . . . . . . . . . . . . . . . . . . . . . 10
1.3.3.4 Geometric verification and robust estimators . . . . . . . . . 13
1.3.3.5 Joint methods . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.3.4 Initial parameterization . . . . . . . . . . . . . . . . . . . . . . . . . . 19
1.3.5 Bundle adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
1.3.6 Dense reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
1.3.7 Georeferencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
1.4 Research objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2 Generation of a benchmark dataset using historical photographs for the evaluation
of feature matching methods 29
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.1.1 Image differences based on digitization and image medium . . . . . . . 30
2.1.2 Image differences based on different cameras and acquisition technique 31
2.1.3 Object differences based on different dates of acquisition . . . . . . . . 31
2.2 Related work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.3 The image dataset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.4 Comparison of different feature detection and description methods . . . . . . 35
2.4.1 Oriented FAST and Rotated BRIEF (ORB) . . . . . . . . . . . . . . . 36
2.4.2 Maximally Stable Extremal Region Detector (MSER) . . . . . . . . . 36
2.4.3 Radiation-invariant Feature Transform (RIFT) . . . . . . . . . . . . . 36
2.4.4 Feature matching and outlier removal . . . . . . . . . . . . . . . . . . 36
2.5 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.6 Conclusions and future work . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3 Photogrammetry as a link between image repository and 4D applications 45
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
IX
Contents
3.2 Multimodal access on repositories . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.2.1 Conventional access . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.2.2 Virtual access using online collections . . . . . . . . . . . . . . . . . . 48
3.2.3 Virtual museums . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
3.3 Workflow and access strategies . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.3.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.3.2 Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.3.3 Photogrammetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.3.4 Browser access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
3.3.5 VR and AR access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
3.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4 An adapted Structure-from-Motion Workflow for the orientation of historical
images 69
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.2 Related Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.2.1 Historical images for 3D reconstruction . . . . . . . . . . . . . . . . . 72
4.2.2 Algorithmic Feature Detection and Matching . . . . . . . . . . . . . . 73
4.2.3 Feature Detection and Matching using Convolutional Neural Networks 74
4.3 Feature Matching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
4.4 Workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
4.4.1 Step 1: Data preparation . . . . . . . . . . . . . . . . . . . . . . . . . 78
4.4.2 Step 2.1: Feature Detection and Matching . . . . . . . . . . . . . . . . 78
4.4.3 Step 2.2: Vanishing Point Detection and Principal Distance Estimation 80
4.4.4 Step 3: Scene Reconstruction . . . . . . . . . . . . . . . . . . . . . . . 80
4.4.5 Comparison with Three Other State-of-the-Art SfM Workflows . . . . 81
4.5 Datasets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
4.6 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
4.7 Conclusions and Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
4.8 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
4.A Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
5 Fully automated pose estimation of historical images 97
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
5.2 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
5.2.1 Image Retrieval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
5.2.2 Feature Detection and Matching . . . . . . . . . . . . . . . . . . . . . 101
5.3 Data Preparation: Image Retrieval . . . . . . . . . . . . . . . . . . . . . . . . 102
5.3.1 Experiment and Data . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
5.3.2 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
5.3.2.1 Layer Extraction Approach (LEA) . . . . . . . . . . . . . . . 104
5.3.2.2 Attentive Deep Local Features (DELF) Approach . . . . . . 105
5.3.3 Results and Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 106
5.4 Camera Pose Estimation of Historical Images Using Photogrammetric Methods 110
5.4.1 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
5.4.1.1 Benchmark Datasets . . . . . . . . . . . . . . . . . . . . . . . 111
5.4.1.2 Retrieval Datasets . . . . . . . . . . . . . . . . . . . . . . . . 113
5.4.2 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
5.4.2.1 Feature Detection and Matching . . . . . . . . . . . . . . . . 115
5.4.2.2 Geometric Verification and Camera Pose Estimation . . . . . 116
5.4.3 Results and Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 117
5.5 Conclusions and Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
5.A Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
6 Related publications 129
6.1 Photogrammetric analysis of historical image repositores for virtual reconstruction
in the field of digital humanities . . . . . . . . . . . . . . . . . . . . . . . 130
6.2 Feature matching of historical images based on geometry of quadrilaterals . . 131
6.3 Geo-information technologies for a multimodal access on historical photographs
and maps for research and communication in urban history . . . . . . . . . . 132
6.4 An automated pipeline for a browser-based, city-scale mobile 4D VR application
based on historical images . . . . . . . . . . . . . . . . . . . . . . . . . . 133
6.5 Software and content design of a browser-based mobile 4D VR application to
explore historical city architecture . . . . . . . . . . . . . . . . . . . . . . . . 134
7 Synthesis 135
7.1 Summary of the developed workflows . . . . . . . . . . . . . . . . . . . . . . . 135
7.1.1 Error assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
7.1.2 Accuracy estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
7.1.3 Transfer of the workflow . . . . . . . . . . . . . . . . . . . . . . . . . . 141
7.2 Developments and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
8 Appendix 149
8.1 Setup for the feature matching evaluation . . . . . . . . . . . . . . . . . . . . 149
8.2 Transformation from COLMAP coordinate system to OpenGL . . . . . . . . 150
References 151
List of Figures 165
List of Tables 167
List of Abbreviations 169
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Likelihood Ratio Combination of Multiple Biomarkers and Change Point Detection in Functional Time SeriesDu, Zhiyuan 24 September 2024 (has links)
Utilizing multiple biomarkers in medical research is crucial for the diagnostic accuracy of detecting diseases. An optimal method for combining these biomarkers is essential to maximize the Area Under the Receiver Operating Characteristic (ROC) Curve (AUC). The optimality of the likelihood ratio has been proven but the challenges persist in estimating the likelihood ratio, primarily on the estimation of multivariate density functions. In this study, we propose a non-parametric approach for estimating multivariate density functions by utilizing Smoothing Spline density estimation to approximate the full likelihood function for both diseased and non-diseased groups, which compose the likelihood ratio. Simulation results demonstrate the efficiency of our method compared to other biomarker combination techniques under various settings for generated biomarker values. Additionally, we apply the proposed method to a real-world study aimed at detecting childhood autism spectrum disorder (ASD), showcasing its practical relevance and potential for future applications in medical research.
Change point detection for functional time series has attracted considerable attention from researchers. Existing methods either rely on FPCA, which may perform poorly with complex data, or use bootstrap approaches in forms that fall short in effectively detecting diverse change functions. In our study, we propose a novel self-normalized test for functional time series implemented via a non-overlapping block bootstrap to circumvent reliance on FPCA. The SN factor ensures both monotonic power and adaptability for detecting diverse change functions on complex data. We also demonstrate our test's robustness in detecting changes in the autocovariance operator. Simulation studies confirm the superior performance of our test across various settings, and real-world applications further illustrate its practical utility. / Doctor of Philosophy / In medical research, it is crucial to accurately detect diseases and predict patient outcomes using multiple health indicators, also known as biomarkers. Combining these biomarkers effectively can significantly improve our ability to diagnose and treat various health conditions. However, finding the best way to combine these biomarkers has been a long-standing challenge. In this study, we propose a new, easy-to-understand method for combining multiple biomarkers using advanced estimation techniques. Our method takes into account various factors and provides a more accurate way to evaluate the combined information from different biomarkers. Through simulations, we demonstrated that our method performs better than other existing methods under a variety of scenarios. Furthermore, we applied our new method to a real-world study focusing on detecting childhood autism spectrum disorder (ASD), highlighting its practical value and potential for future applications in medical research.
Detecting changes in patterns over time, especially shifts in averages, has become an important focus in data analysis. Existing methods often rely on techniques that may not perform well with more complex data or are limited in the types of changes they can detect. In this study, we introduce a new approach that improves the accuracy of detecting changes in complex data patterns. Our method is flexible and can identify changes in both the mean and variation of the data over time. Through simulations, we demonstrate that this approach is more accurate than current methods. Furthermore, we applied our method to real-world climate research data, illustrating its practical value.
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