Building Footprint Extraction from LiDAR Data and Imagery Information

This study presents an automatic method for regularisation of building outlines. Initially, building segments are extracted using a new fusion method. Data- and model-driven approaches are then combined to generate approximate building polygons. The core part of the method includes a novel data-driven algorithm based on likelihood equation derived from the geometrical properties of a building. Finally, the Gauss-Helmert and Gauss-Markov models adjustment are implemented and modified for regularisation of building outlines considering orthogonality constraints

VLSI Routing for Advanced Technology

Routing is a major step in VLSI design, the design process of complex integrated circuits (commonly known as chips). The basic task in routing is to connect predetermined locations on a chip (pins) with wires which serve as electrical connections. One main challenge in routing for advanced chip technology is the increasing complexity of design rules which reflect manufacturing requirements. In this thesis we investigate various aspects of this challenge. First, we consider polygon decomposition problems in the context of VLSI design rules. We introduce different width notions for polygons which are important for width-dependent design rules in VLSI routing, and we present efficient algorithms for computing width-preserving decompositions of rectilinear polygons into rectangles. Such decompositions are used in routing to allow for fast design rule checking. A main contribution of this thesis is an O(n) time algorithm for computing a decomposition of a simple rectilinear polygon with n vertices into O(n) rectangles, preseverving two-dimensional width. Here the two-dimensional width at a point of the polygon is defined as the edge length of a largest square that contains the point and is contained in the polygon. In order to obtain these results we establish a connection between such decompositions and Voronoi diagrams. Furthermore, we consider implications of multiple patterning and other advanced design rules for VLSI routing. The main contribution in this context is the detailed description of a routing approach which is able to manage such advanced design rules. As a main algorithmic concept we use multi-label shortest paths where certain path properties (which model design rules) can be enforced by defining labels assigned to path vertices and allowing only certain label transitions. The described approach has been implemented in BonnRoute, a VLSI routing tool developed at the Research Institute for Discrete Mathematics, University of Bonn, in cooperation with IBM. We present experimental results confirming that a flow combining BonnRoute and an external cleanup step produces far superior results compared to an industry standard router. In particular, our proposed flow runs more than twice as fast, reduces the via count by more than 20%, the wiring length by more than 10%, and the number of remaining design rule errors by more than 60%. These results obtained by applying our multiple patterning approach to real-world chip instances provided by IBM are another main contribution of this thesis. We note that IBM uses our proposed combined BonnRoute flow as the default tool for signal routing

Simplifying Urban Data Fusion with BigSUR

Our ability to understand data has always lagged behind our ability to collect it. This is particularly true in urban environments, where mass data capture is particularly valuable, but the objects captured are more varied, dense, and complex. Captured data has several problems; it is unstructured (we do not know which objects are encoded by the data), contains noise (the scanning process is often inaccurate) and omissions (it is often impossible to scan all of a building). To understand the structure and content of the environment, we must process the unstructured data to a structured form. BigSURi is an urban reconstruction algorithm which fuses GIS (Geographic Information System / mapping) data, photogrammetric meshes, and street level photography, to create clean representative, semantically labelled, geometry. However, we have identified three problems with the system i) the street level photography is often difficult to acquire; ii) novel façade styles often frustrate the detection of windows and doors; iii) the computational requirements of the system are large, processing a large city block can take up to 15 hours. Here we describe the process of simplifying and validating the BigSUR semantic reconstruction system. In particular, the requirement for street level images is removed, and a greedy post-process profile assignment is introduced to accelerate the system. We accomplish this by modifying the binary integer programming (BIP) optimization, and re-evaluating the effects of various parameters. The new variant of the system is evaluated over a variety of urban areas. We objectively measure mean squared error (MSE) terms over the unstructured geometry, showing that BigSUR is able to accurately recover omissions and discard inaccuracies in the input data. Further, we evaluate the ability of the system to label the walls and roofs of input meshes, concluding that our new BigSUR variant achieves highly accurate semantic labelling with shorter computational time and less input data

Using an anisotropic diffusion scale-space for the detection and delineation of shacks in informal settlement imagery

PhD, Faculty of Engineering and the Built Environment, University of the Witwatersrand, 2010Informal settlements are a growing world-wide phenomenon. Up-to-date spatial information mapping settlements is essential for a variety of end-user applications from planning settlement upgrading to monitoring expansion and infill. One method of gathering this information is through the analysis of nadir-view aerial imagery and the automated or semi-automated extraction of individual shacks. The problem of shack detection and delineation in, particularly South African, informal settlements is a unique and difficult one. This is primarily due to the inhomogeneous appearance of shack roofs, which are constructed from a variety of disparate materials, and the density of shacks. Previous research has focused mostly on the use of height data in conjunction with optical images to perform automated or semi-automated shack extraction. In this thesis, a novel approach to automating shack extraction is presented and prototyped, in which the appearance of shack roofs is homogenised, facilitating their detection. The main features of this strategy are: construction of an anisotropic scale-space from a single source image and detection of hypotheses at multiple scales; simplification of hypotheses' boundaries through discrete curve evolution and regularisation of boundaries in accordance with an assumed shack model - a 4-6 sided, compact, rectilinear shape; selection of hypotheses competing across scales using fuzzy rules; grouping of hypotheses based on their support for one another, and localisation and re-regularisation of boundaries through the incorporation of image edges. The prototype's performance is evaluated in terms of standard metrics and is analysed for four different images, having three different sets of imaging conditions, and containing well over a hundred shacks. Detection rates in terms of building counts vary from 83% to 100% and, in terms of roof area coverage, from 55% to 84%. These results, each derived from a single source image, compare favourably with those of existing shack detection systems, especially automated ones which make use of richer source data. Integrating this scale-space approach with height data offers the promise of even better results

Algorithmic Beauty of Buildings Methods for Procedural Building Generation

As virtual reality simulations, video games, and computer animated movies become more prevalent, the need arises to generate the content the three-dimensional models via an algorithm rather than crafting them by hand. Previous research in the area of procedural building generation has focused merely on the external appearance of commercial buildings. These methods are unsatisfactory for certain applications due to the lack of a walk-through feature. A new algorithm is proposed to generate residential units with realistic floor plans based partially on the architectural observations of Christopher Alexander. Results for the algorithm display real-time performance and a resemblance to real home floor plans. Also, a complex algorithmic framework for generating hyper-realistic residential units is described, along with algorithms that operate within the framework to generate more realistic residential units. The results of these two methods of residential unit generation are analyzed and the implications of this analysis is discussed. Future research areas are also suggested

Voronoi diagram of orthogonal polyhedra in two and three dimensions

Τα διαγράμματα Voronoi αποτελούν μία θεμελιώδη γεωμετρική δομή δεδομένων και έκφραζουν αποστάσεις σημείων στο χώρο από ένα σύνολο αντικειμένων. Θεωρούμε ορθογώνια πολύεδρα ευθυγραμμισμένα με τους άξονες. Πρόκειται για πολύεδρα των οποίων οι έδρες σχηματίζουν ορθές γωνίες, και οι ακμές είναι παράλληλες προς τους άξονες ενός καρτεσιανού συστήματος συντεταγμένων. Κατασκευάζουμε το διάγραμμα Voronoi στο εσωτερικό ενός ορθογώνιου πολυέδρου με τρύπες που ορίζονται από αντίστοιχα πολύεδρα, χρησιμοποιώντας την max-νόρμα. Πρόκειται για έναν συνδυασμό που βρίσκει πολλές εφαρμογές σε τομείς όπως τα raster graphics και ο σχεδιασμός κυκλωμάτων VLSI. Παρουσιάζουμε έναν αλγόριθμο για την κατασκευή αυτών των διαγραμμάτων Voronoi σε δύο και τρεις διαστάσεις. Ακολουθούμε τη μέθοδο υποδιαίρεσης και βασιζόμαστε σε μία δομή δεδομένων από bounding-volumes: πρόκειται για μία μή τετριμμένη προσέγγιση του προβλήματος. Επιπλέον αναλύουμε την πολυπλοκότητα του αλγορίθμου, η οποία είναι γραμμική κάτω από μία υπόθεση ομοιόμορφα κατανεμημένης εισόδου. Μέρος της παρούσας εργασίας πρόκειται να δημοσιευθεί στα πρακτικά του συνεδρίου SEA^2 2019 (Special Event on Analysis of Experimental Algorithms).Voronoi diagrams are a fundamental geometric data structure for obtaining proximity relations. We consider axis-aligned orthogonal polyhedra in two and three-dimensional space. These are polyhedra whose faces meet at right angles and their edges are aligned with the axes of a coordinate system. We construct the exact Voronoi diagram inside an axis-aligned orthogonal polyhedron with holes defined by such polyhedra, under the max-norm. This is a particularly useful scenario in certain application domains, including raster graphics and VLSI design. Our approach avoids creating full-dimensional elements on the Voronoi diagram and yields a skeletal representation of the input object, equivalent to the straight skeleton. We introduce a complete algorithm in 2D and 3D that follows the subdivision paradigm relying on a bounding-volume hierarchy; this is an original approach to the problem. The algorithm reads in a region bounding the input polyhedron and performs a recursive subdivision into cells (using quadtrees and octrees for 2D and 3D resp.). Then, a reconstruction technique is applied to produce an isomorphic representation of the Voronoi diagram. An hierarchical data structure of bounding volumes is used to accelerate the 2D algorithm for certain inputs and is necessary for the efficiency of the 3D algorithm. The complexity is adaptive and comparable to that of previous methods. Under a mild assumption it is O(n / D+1 / D^2) in 2D or O(n a ^2 / D^2+1 / D^3) in 3D, where n is the number of sites, namely edges or facets respectively, D is the maximum cell size for the subdivision to stop (and is <1 under the appropriate scaling), and a bounds vertex cardinality per facet. We also provide a numerically stable, open-source implementation in Julia, illustrating the practical nature of our algorithm. Part of the current thesis is given in the paper "Voronoi diagram of orthogonal polyhedra in two and three dimensions", co-authored with Prof. Ioannis Z. Emiris, that is about to appear in Proceedings of SEA^2 2019 (Special Event on Analysis of Experimental Algorithms)

Reciprocal frame structures

This thesis attempts an investigation of the Reciprocal Frame (RF) structure from the architectural point of view. The Introduction (Chapter 1) sets out the research subject and introduces the reader to the RF structure. Chapter 2 investigates the origin of the structure and offers a survey of similar types of systems used throughout human history. Also, a review of 'kinetic' forms of architecture is presented. Chapter 3 investigates Japanese RF construction and the possible reasons for the emergence of the system in Japan as early as the 12th century. Chapter 4 examines the potential of the system for modular construction of both temporary and permanent RF buildings, with a review of RF modular buildings constructed in the UK. Chapter 5 explores different RF morphologies on a student project case study, as well as their design experiences and opinions when using the RF system. More practical issues regarding the RF are presented in Chapter 6 which investigates the parameters which define the 2-dimensional and 3-dimensional geometry of the system and their variation, methods for simplifying the CAD presentation of the structure, alternative covering systems, and the possibility of using the RF as a retractable roof. Chapter 7 offers conclusions and aspects of future research on the system. The Appendices at the end include: two types of questionnaires and the complete transcribed interviews used to examine the students' design experiences and opinions, a routine in AutoLISP written by the author which simplifies the CAD presentation of the RF, and copies of the five Conference papers published using the findings of this research project

Reconstructing The Social Landscape Of Cerro Arena, Peru

This thesis deals with the 2017 archaeological survey of the site of Cerro Arena, in the Moche Valley, Peru. The site belongs to the Salinar phase (c.a 400–0 BCE), known to be a time of increased warfare and cultural fragmentation. During this time, Cerro Arena became the largest settlement in the valley, housing a large number of people in structures densely packed into the elevated terrain of the site. Yet, information on the spatial arrangement of civic and residential architecture was lacking. Using remote sensing techniques—primarily Unmanned Aerial Vehicles (UAVs) —and Geographic Information Systems (GIS), we sought to create high-resolution models of the site from which to map all architectural remains. We use several analyses to document life on this ancient Andean settlement

Urban ground-based thermography

Urban climates are driven by micro-meteorological processes associated with the complex urban form, materials, and land cover patterns. Given its close link to the surface energy balance, surface temperature observations are key to the improvement and evaluation of models. This work contributes to the application of ground-based thermography in urban settings as an observational method to further our understanding of urban climate processes. In this thesis, ground-based thermography observations are collected and interpreted in a unique way so that they are relatable to scales used by urban climate models and earth observation (EO) satellites. At two measurement sites (simplified outdoor scale model and complex central urban setting), variations in surface temperature are quantitatively linked to micro-scale features such as shadow patterns and material characteristics at unprecedented levels of detail. Previous studies with low level of detail have inferred these properties. The detected upwelling longwave radiation is corrected to surface temperature (Ts) using a novel, high-resolution three-dimensional (3D) radiative transfer (RT) approach. From multi-day observational evaluation, the atmospheric correction has 0.39 K mean absolute error. Ground-based observations are combined with a comprehensive 3D radiative transfer model, enabling detailed simulation of EO land surface temperature (TsEO). For a mainly clear-sky summer day, TsEO at night underestimates the unbiased “complete” surface temperature (Tc) by 0.5 – 1 K, is similar to Tc during morning and evening, and for other times varies significantly with view angle (up to 5.1 K). Generally, view angle variation is smaller than prior studies as they typically use simpler geometry and temperature descriptions, and lack vegetation. Here, the observational basis and high-resolution modelling in a real central urban setting serves as a benchmark for future improvements of simplified model parameterisations

Architectural Digital Photogrammetry

This study is to exploit texturing techniques of a common modelling software in the way of creating virtual models of an exist architectures using oriented panoramas. In this research, The panoramic image-based interactive modelling is introduced as assembly point of photography, topography, photogrammetry and modelling techniques. It is an interactive system for generating photorealistic, textured 3D models of architectural structures and urban scenes. The technique is suitable for the architectural survey because it is not a «point by point» survey, and it exploit the geometrical constraints in the architecture to simplify modelling. Many factors are presented to be critical features that affect the modelling quality and accuracy, such as the way and the position in shooting the photos, stitching the multi-image panorama photos, the orientation, texturing techniques and so on. During the last few years, many Image-based modelling programmes have been released. Whereas, in this research, the photo modelling programs was not in use, it meant to face the fundamentals of the photogrammetry and to go beyond the limitations of such software by avoiding the automatism. In addition, it meant to exploit the potent commands of a program as 3DsMax to obtain the final representation of the Architecture. Such representation can be used in different fields (from detailed architectural survey to an architectural representation in cinema and video games), considering the accuracy and the quality which they are vary too. After the theoretical studies of this technique, it was applied in four applications to different types of close range surveys. This practice allowed to comprehend the practical problems in the whole process (from photographing all the way to modelling) and to propose the methods in the ways to improve it and to avoid any complications. It was compared with the laser scanning to study the accuracy of this technique. Thus, it is realized that not only the accuracy of this technique is linked to the size of the surveyed object, but also the size changes the way in which the survey to be approached. Since the 3D modelling program is not dedicated to be used for the image-based modelling, texturing problems was faced. It was analyzed in: how the program can behave with the Bitmap, how to project it, how it could be an interactive projection, and what are the limitations