Super-resolution-based snake model—an unsupervised method for large-scale building extraction using airborne LiDAR Data and optical image

Automatic extraction of buildings in urban and residential scenes has become a subject of growing interest in the domain of photogrammetry and remote sensing, particularly since the mid-1990s. Active contour model, colloquially known as snake model, has been studied to extract buildings from aerial and satellite imagery. However, this task is still very challenging due to the complexity of building size, shape, and its surrounding environment. This complexity leads to a major obstacle for carrying out a reliable large-scale building extraction, since the involved prior information and assumptions on building such as shape, size, and color cannot be generalized over large areas. This paper presents an efficient snake model to overcome such a challenge, called Super-Resolution-based Snake Model (SRSM). The SRSM operates on high-resolution Light Detection and Ranging (LiDAR)-based elevation images—called z-images—generated by a super-resolution process applied to LiDAR data. The involved balloon force model is also improved to shrink or inflate adaptively, instead of inflating continuously. This method is applicable for a large scale such as city scale and even larger, while having a high level of automation and not requiring any prior knowledge nor training data from the urban scenes (hence unsupervised). It achieves high overall accuracy when tested on various datasets. For instance, the proposed SRSM yields an average area-based Quality of 86.57% and object-based Quality of 81.60% on the ISPRS Vaihingen benchmark datasets. Compared to other methods using this benchmark dataset, this level of accuracy is highly desirable even for a supervised method. Similarly desirable outcomes are obtained when carrying out the proposed SRSM on the whole City of Quebec (total area of 656 km2), yielding an area-based Quality of 62.37% and an object-based Quality of 63.21%

3D data modelling and processing using partial differential equations.

NoIn this paper we discuss techniques for 3D data modelling and processing where the data are usually provided as point clouds which arise from 3D scanning devices. The particular approaches we adopt in modelling 3D data involves the use of Partial Differential Equations (PDEs). In particular we show how the continuous and discrete versions of elliptic PDEs can be used for data modelling. We show that using PDEs it is intuitively possible to model data corresponding to complex scenes. Furthermore, we show that data can be stored in compact format in the form of PDE boundary conditions. In order to demonstrate the methodology we utlise several examples of practical nature

Improved facial feature fitting for model based coding and animation

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The promise of interconnecting problems for enriching students’ experiences in mathematics

The interconnecting problem approach suggests that often one and the same mathematical problem can be used to teach various mathematical topics at different grade levels. How is this approach useful for the development of mathematical ability and the enrichment of mathematical experiences of all students including the gifted ones? What are the benefits for teachers’ and what would teachers need to implement this approach? What directions would further research on these issues take? The paper discusses these and closely related questions. I propose that a long-term study of a progression of mathematical ideas revolved around one interconnecting problem is useful for developing a perception of mathematics as a connected subject for all learners. Having a natural appreciation for linking learned material, mathematically-able students exposed to this approach could develop more comprehensive thinking, applicable in many other problem solving situations, such as multiple-solution tasks. Because the problem’s solutions vary in levels of difficulty, as well as conceptual richness, the approach allows teachers to form a strategic vision through a systematic review of various mathematical topics in connection with one problem. General pedagogical ideas outlined in this paper are supported by discussions of concrete mathematical examples and classroom applications. While individual successful practices of using this approach are known to be taking place, the need for more data collection and interpretation is highlighted

Geometric confinement of thin films: From crumple formation to curvature-induced propulsion

Thin films can undergo large amplitude nonlinear deformation even under a small applied force which makes predicting their behavior rather challenging. This dissertation focuses on two phenomena in thin films: the morphological transition from sharp to smooth microstructures in geometrically-confined sheets, and a novel locomotion behavior of a thin floating film placed on an interface with a curvature gradient. In the first portion of the thesis, we use inflated membranes as model system to understand morphological transitions in confined films. We have developed methods to make air-tight membranes out of sheets of materials with varying Young\u27s modulus and thickness. We have observed that increasing the internal pressure in the membranes causes some sharp-edged diamond-like structures called crumples to form. On further increase in pressure, these crumples transition to smooth periodic wrinkles. We have measured this transition pressure across a wide range of materials and geometries. We collect our data, as well as data from other experiments on interfacial polymer films, in an empirical phase diagram for the transition from wrinkles to crumples. We further study the topography of the crumpling pattern on the surface of the membrane and its relation to d-cones. Small-scale structures like wrinkles and crumples can enable macroscopic shape change of an entire sheet. In the second part of this thesis, we explore how shape changes of a film (through small-scale wrinkling) can enable a film to feel body forces when placed on a liquid with a non-uniform curvature. This study is motivated by examples from nature: arthropod species that exploit the surface tension of water for aquatic locomotion. Current literature addresses stiff or finitely bendable materials that retain their shape on liquid meniscus where the fluid adjusts its interface to accommodate them via an interplay of surface tension and buoyancy or gravity. We introduce an unexplored setting where thin monotonous film that can easily deform by capillary forces is placed on a positively curved liquid meniscus. A thin film can conform to a curved meniscus by forming small-amplitude wrinkles. Once released, it sets in motion towards the flat center while returning to its symmetrical state. We are able to identify the complex mechanics of propulsion experienced by thin film through numerical simulations using Surface Evolver. Our results give a closer look at the velocity of thin film and energetics of the system and its dependence on the position of the sheet on the interface. Our finding curiously shows that an unstretchable film progresses 10 times faster than the same film with finite stretching indicating the importance of elasticity in such systems

Respiratory organ motion in interventional MRI : tracking, guiding and modeling

Respiratory organ motion is one of the major challenges in interventional MRI, particularly in interventions with therapeutic ultrasound in the abdominal region. High-intensity focused ultrasound found an application in interventional MRI for noninvasive treatments of different abnormalities. In order to guide surgical and treatment interventions, organ motion imaging and modeling is commonly required before a treatment start. Accurate tracking of organ motion during various interventional MRI procedures is prerequisite for a successful outcome and safe therapy. In this thesis, an attempt has been made to develop approaches using focused ultrasound which could be used in future clinically for the treatment of abdominal organs, such as the liver and the kidney. Two distinct methods have been presented with its ex vivo and in vivo treatment results. In the first method, an MR-based pencil-beam navigator has been used to track organ motion and provide the motion information for acoustic focal point steering, while in the second approach a hybrid imaging using both ultrasound and magnetic resonance imaging was combined for advanced guiding capabilities. Organ motion modeling and four-dimensional imaging of organ motion is increasingly required before the surgical interventions. However, due to the current safety limitations and hardware restrictions, the MR acquisition of a time-resolved sequence of volumetric images is not possible with high temporal and spatial resolution. A novel multislice acquisition scheme that is based on a two-dimensional navigator, instead of a commonly used pencil-beam navigator, was devised to acquire the data slices and the corresponding navigator simultaneously using a CAIPIRINHA parallel imaging method. The acquisition duration for four-dimensional dataset sampling is reduced compared to the existing approaches, while the image contrast and quality are improved as well. Tracking respiratory organ motion is required in interventional procedures and during MR imaging of moving organs. An MR-based navigator is commonly used, however, it is usually associated with image artifacts, such as signal voids. Spectrally selective navigators can come in handy in cases where the imaging organ is surrounding with an adipose tissue, because it can provide an indirect measure of organ motion. A novel spectrally selective navigator based on a crossed-pair navigator has been developed. Experiments show the advantages of the application of this novel navigator for the volumetric imaging of the liver in vivo, where this navigator was used to gate the gradient-recalled echo sequence

Design of an unmanned, reusable vehicle to de-orbit debris in Earth orbit

The space debris problem is becoming more important because as orbital missions increase, the amount of debris increases. It was the design team's objective to present alternative designs and a problem solution for a deorbiting vehicle that will alleviate the problem by reducing the amount of large debris in earth orbit. The design team was asked to design a reusable, unmanned vehicle to de-orbit debris in earth orbit. The design team will also construct a model to demonstrate the system configuration and key operating features. The alternative designs for the unmanned, reusable vehicle were developed in three stages: selection of project requirements and success criteria, formulation of a specification list, and the creation of alternatives that would satisfy the standards set forth by the design team and their sponsor. The design team selected a Chain and Bar Shot method for deorbiting debris in earth orbit. The De-orbiting Vehicle (DOV) uses the NASA Orbital Maneuvering Vehicle (OMV) as the propulsion and command modules with the deorbiting module attached to the front

High resolution aerial and field mapping of thermal features in Ragged Hills, Yellowstone National Park

High resolution aerial images taken in a cost and time effective way from low-flying platforms were used to map a hydrothermal area in the Yellowstone National Park. The mapping area called Ragged Hills is located in the Norris Geyser Basin, a major hydrothermal basin of the Park famous for its great diversity and number of thermal features. Because of an increasing thermal activity since the early 1990s numerous hydrothermal features of different sizes developed in Ragged Hills. Various changes in size and chemistry of the thermal features were observed during sporadic ground surveys. No detailed maps of the thermal inventory existed because of the difficulties in mapping this rapidly changing area by standard ground survey methods. Mapping the features in a short time to get a status quo of the feature’s form and size was the goal of the present work. Two different low-flying platforms were used during this project – a helium filled balloon and a single engine airplane (Cessna 172). To be able to georeference the aerial photos later a grid of ground control points was laid out and the points were surveyed by differential GPS as well as by theodolite. Deviations between both methods were on average 37 cm (Northing) and 61 cm (Easting). The overflights with the airplane were more cost intensive, requiring aircraft rental and trained pilots. Because the obtained images were in most cases blurred, they were served as overview only. Nevertheless the pixel resolution was quiet good with an average of 6 cm. Besides the true color images taken by a digital camera, also thermal pictures were taken from the airplane with a spatial resolution of 1.2 m. The balloon survey provided a costeffective and easy-to-handle alternative. Major restrictions are only the transport of the helium bottles to the study site, and the requirements for calm wind conditions. From an altitude of 50 to 80 m sharp and high resolution images were obtained. About 45 pictures were used to create a mosaic of the whole study area with a pixel resolution of 2.5 cm. No high-resolution thermal pictures could be taken from the balloon because the weight of the camera (3.9 kg) exceeded the balloon’s lifting capacity (1.5 kg). The created high-resolution aerial overview was included in a digital atlas together with topography and geological maps, older lowresolution aerial pictures, and hydrochemical data. The following diploma thesis gives an overview about available low-flying platforms and their individual advantages and disadvantages, describes the methods used in detail and evaluates them regarding expenditure and time it took to realize the individual working steps. Furthermore an interpretation of mapping and hydrochemical data is presented.Förderkreis Freiberger Geologie e.V.researc