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Lewis, Michael. "Data compression for digital elevation models." Thesis, University of South Wales, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265470.
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Wood, Joseph. "The geomorphological characterisation of Digital Elevation Models." Thesis, University of Leicester, 1996. http://hdl.handle.net/2381/34503.
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Techniques and issues are considered surrounding the characterisation of surface form represented by Digital Elevation Models (DEMs). A set of software tools suitable for use in a raster based Geographical Information System (GIS) is developed. Characterisation has three specific objectives, namely to identify spatial pattern, to identify scale dependency in form and to allow visualisation of results. An assessment is made of the characteristics of error in DEMs by identifying suitable quantitative measures and visualisation processes that may be enabled within a GIS. These are evaluated by contour threading a fractal surface and comparing four different spatial interpolations of the contours. The most effective error characterisations are found to be those that identify high frequency spatial pattern. Visualisation of spatial arrangement of DEM error is used to develop a deterministic error model based on local surface slope and aspect. DEMs are parameterised using first and second derivatives of quadratic surfaces fitted over a range of scales. This offers advantages over traditional methods based on a 3 by 3 local window, as geomorphometric form can be characterised at any scale. Morphometric parameters are combined to give a feature classification that may also be applied over a range of scales. Multi-scale measurements are combined to give a feature membership function that describes how properties change with scale. These functions are visualised using modal and entropy measures of variability. An additional method of visualising scale dependency is suggested that graphically represents statistical measures of spatial pattern over a variety of spatial lags. This is found most appropriate for detecting structural anisotropy in a surface. Characterisation tools are evaluated by applying them to uncorrelated surfaces, fractal surfaces and Ordnance Survey DEMs of Lake District, Peak District and Dartmoor.
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Hughes, Lesley Ann. "The robust compression of digital elevation models." Thesis, University of South Wales, 2000. https://pure.southwales.ac.uk/en/studentthesis/the-robust-compression-of-digital-elevation-models(6ef3e8dd-cc49-4d52-b8a3-b2c49ca0dfc9).html.
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The representation of terrain by a regular grid Digital Elevation Model (DEM) requires a large amount of data which increases with the resolution. The nature of the typical applications of terrain data, for example, aeronautical navigation, dictates that the reliability of the data is of prime importance. Thus any compression scheme used for compressing OEMs, in the presence of errors, must be able to achieve competitive compression while retaining a level of accuracy in the decompressed data. The requirements for effective data compression and error control tend to conflict. In some situations, for example, mobile storage devices used in hostile environments, the use of both techniques is essential. In this research the use of data compression for a storage channel subject to error is considered. The suitability of some standard data compression techniques (statistical and dictionary based methods) for robust terrain compression, is examined. The results indicate, as expected, that these methods, as they stand, are unable to tolerate any error in the compressed data. Five possible methods for the robust progressive compression of terrain data, based on common image and other compression methods, are developed and implemented. The five methods are a bit splitting method, a grid interpolation method, a discrete cosine transform based method, a vector quantization based method and a linear quadtree method. All methods are used in conjunction with a statistical encoder. Each method identifies the information critical for obtaining a good approximation to the original terrain, and thus the information which requires strong error control. It is shown that grid interpolation is the natural choice for lossless robust DEM compression. A progressive strategy which incorporates various levels of data is employed. The levels are formed by down-sampling the data to form a coarse and fine grid of elevations. Grid interpolation techniques are then employed to obtain an approximation of the fine grid from the coarse grid. The corrections to this approximation are then compressed using an arithmetic encoder. This process is done repeatedly to produce the required number of levels. Protection is achieved primarily through the use of BCH codes. The protection is incorporated in such a way that the coarsest levels of data receive stronger error control. Secondary error detection mechanisms exist through the use of the arithmetic encoder and also some prior knowledge of the compressed data. The software developed here proves to be successful with regard to progressively reconstructing terrain in the presence of errors, while also producing compression results which compare favourably with theoretical results based on a known DEM compression method. Consideration is also given to the task of validating the decompressed data, and determining if terrain data may be distinguished from other digital data. A series of tests which use the grid interpolation and DCT methods discussed previously are used, along with Moran's Index, to measure spatial auto correlation. Local tests based on image processing techniques (edge and point detection masks) are also employed to detect any anomalies in data which may otherwise be classified as terrain. The results indicate that while the differentiation of terrain and uncorrelated data is a relatively straightforward task, the task of distinguishing between terrain data and other correlated data provides great scope for further research.
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Premalatha, M. "Quality assessment of interferometrically derived digital elevation models." Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441542.
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Saha, Kakoli. "Object-Oriented classification of drumlins from Digital Elevation Models." Kent State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=kent1289558937.
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Abd, Aziz Samsuzana. "Development of digital elevation models (DEMs) for agricultural applications." [Ames, Iowa : Iowa State University], 2008.
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Dowson, Kurt. "Towards extracting artistic sketches and maps from digital elevation models." Thesis, University of Hull, 1994. http://hydra.hull.ac.uk/resources/hull:3566.
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The main trend of computer graphics is the creation of photorealistic images however, there is increasing interest in the simulation of artistic and illustrative techniques. This thesis investigates a profile based technique for automatically extracting artistic sketches from regular grid digital elevation models. The results resemble those drawn by skilled cartographers and artists.The use of cartographic line simplification algorithms, which are usually applied to complex two-dimensional lines such as coastlines, allow a set of most important points on the terrain surface to be identified, these form the basis for sketching.This thesis also contains a wide ranging review of terrain representation techniques and suggests a new taxonomy.
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RODRIGUES, ANDREY D. ALMEIDA ROCHA. "MULTI-RESOLUTION VISUALIZATION OF DIGITAL ELEVATION MODELS USING GPU SHADERS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=33436@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>PROGRAMA DE EXCELENCIA ACADEMICA<br>A visualização eficiente de grandes modelos digitais de elevação continua sendo um desafio para aplicações em tempo real. O uso direto de novas tecnologias de triangulação em placas gráficas tem uma aplicabilidade limitada no gerenciamento dos níveis de detalhe para grandes modelos. Embora o hardware gráfico seja capaz de controlar a resolução do modelo de um modo bastante eficiente, todos os dados devem estar em memória. Isso compromete a escalabilidade de soluções simples baseadas em GPU para
controlar o nível de detalhe. Neste trabalho, é proposto um novo algoritmo eficiente e escalável para lidar com grandes modelos digitais de elevação. A proposta combina efetivamente a triangulação em GPU com a gerência de ladrilhos em CPU, tirando proveito da capacidade de processamento da GPU ao mesmo tempo que mantém o uso de memória gráfica dentro dos limites práticos. Também é proposta uma técnica para gerenciar o nível de detalhe da imagem aérea mapeada sobre o modelo de elevação como texturas.
Ambas gerências de níveis de detalhe (geometria e textura) executam separadamente, e os ladrilhos são combinados sem a necessidade de carregar qualquer dado adicional. O gerenciamento de níveis de detalhe é então estendido para lidar com modelos com bordas irregulares e buracos.<br>Efficient rendering of large digital elevation models remains as a challenge for real-time applications. The direct use of hardware tessellation has limited applicability for managing level of detail of large models. Although the graphics hardware is capable of controlling the resolution of patches in a very efficient manner, the whole patch data must be loaded in memory. This compromises the scalability of GPU-based naive solutions for controlling level of detail. In this work, we propose an efficient and scalable new
algorithm for large digital elevation models. Our proposal effectively combines GPU tessellation with CPU tile management, taking full advantage of GPU processing capabilities while maintaining graphics-memory use under practical limits. We also propose a technique to manage level of detail of aerial imagery mapped on top of elevation models as textures. Both geometry and texture level of detail management run independently, and tiles are combined with no need to load extra data. The proposed level of detail
management is then extended to handle model with irregular border and holes.
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Teichrieb, Verônica. "Desktop virtual reality in the enchancement of digital elevation models." Universidade Federal de Pernambuco, 2004. https://repositorio.ufpe.br/handle/123456789/2846.
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Previous issue date: 2004<br>Modelos digitais de elevação são representações topográficas. Estes modelos podem conter diversos erros, o que causa incerteza sobre a confiabilidade dos dados. O uso confiável de dados de elevação requer que a incerteza associada aos dados seja levada em consideração e que os erros responsáveis por esta incerteza sejam identificados e removidos. Porém, um problema crítico é o fato de que estes erros podem ser causados por várias razões diferentes em cada modelo digital de elevação gerado, o que torna a sua identificação e a sua correção muito difíceis. Vários estudos propuseram metodologias para detectar e quantificar, e também para remover diferentes tipos de erros. Contudo, estes procedimentos aplicam algoritmos especializados em detectar erros com características particulares, produzindo bons resultados apenas quando o modelo contém predominantemente estes tipos específicos de erros. Atualmente, as metodologias de identificação e de correção de erros de diferentes tipos em modelos digitais de elevação não estão consolidadas e não são eficientes, e não existem ferramentas disponíveis para os usuários de modelos digitais de elevação. Esta tese supre a necessidade de definir métodos para atacar a problemática de erros em modelos digitais de elevação. Para isso, uma metodologia foi definida e uma ferramenta foi implementada para melhorar a qualidade de modelos digitais de elevação. A metodologia é baseada em interfaces de realidade virtual, que permitem a representação precisa de dados complexos, a visualização realista de objetos com formas sofisticadas que possuem características como altura e profundidade, e que são bastante interativas para explorar informações. Um conjunto de técnicas de visualização, interação e navegação, baseadas em interfaces de realidade virtual e adequadas para manipular modelos de terreno, foi definido. De acordo com a metodologia, usuários experientes de modelos digitais de elevação devem realizar três atividades básicas em um ambiente virtual apresentando um modelo digital de elevação tridimensional, para identificar e remover erros. Uma destas três atividades é visualizar e explorar o modelo digital de elevação, a fim de obter conhecimento sobre os dados que pode ser usado para interpretar e verificar visualmente o modelo. Analisar o modelo digital de elevação usando ferramentas de análise especializadas, de forma que características e representações estatísticas podem ser usadas para realizar o controle de qualidade dos dados e identificar áreas de erro no modelo, é outra atividade a ser realizada pelo usuário. Finalmente, uma terceira atividade é a edição de áreas de erro encontradas no conjunto de dados, de forma a melhorar o modelo digital de elevação. O sistema, chamado DEMEditor, foi desenvolvido com base nesta metodologia, para usuários experientes de modelos digitais de elevação. O DEMEditor constrói modelos de realidade virtual desktop baseados em modelos digitais de elevação de radar de abertura sintética interferométrico, e permite a visualização, exploração, análise e edição destes modelos. A realidade virtual desktop está cada vez mais se tornando uma opção atrativa por causa da sua habilidade em construir ambientes bastante realistas e interativos de baixo custo, que podem ser utilizados por qualquer organização. O sistema aperfeiçoa a cadeia de processamento para gerar modelos digitais de elevação de alta precisão; após o processamento dos dados brutos em um modelo digital de elevação, este modelo pode ser analisado de forma a verificar se os dados estão corretos e erros podem ser identificados e corrigidos para melhorá-lo. O DEMEditor foi utilizado para melhorar modelos digitais de elevação gerados a partir de dados reais, através da realização de estudos de caso. De fato, a eficácia do sistema foi confirmada.A interpretação visual tem um papel importante neste trabalho, pois emprega o conhecimento do usuário sobre os dados no processo de tomada de decisão sobre áreas (de erro) a serem melhoradas no modelo digital de elevação. O conhecimento prévio do usuário permite a identificação de qualquer tipo de erro, não havendo a necessidade de utilizar algoritmos de detecção automática especializados em detectar erros com características particulares
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Miller, Matthew Lowell. "Analysis of Viewshed Accuracy with Variable Resolution LIDAR Digital Surface Models and Photogrammetrically-Derived Digital Elevation Models." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/35692.
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The analysis of visibility between two points on the earthâ s terrain is a common use of GIS software. Most commercial GIS software packages include the ability to generate a viewshed, or a map of terrain surrounding a particular location that would be visible to an observer. Viewsheds are often generated using â bare-earthâ Digital Elevation Models (DEMs) derived from the process of photogrammetry. More detailed models, known as Digital Surface Models (DSMs), are often generated using Light Detection and Ranging (LIDAR) which uses an airborne laser to scan the terrain. In addition to having greater accuracy than photogrammetric DEMs, LIDAR DSMs include surface features such as buildings and trees.
This project used a visibility algorithm to predict visibility between observer and target locations using both photogrammetric DEMs and LIDAR DSMs of varying resolution. A field survey of the locations was conducted to determine the accuracy of the visibility predictions and to gauge the extent to which the presence of surface features in the DSMs affected the accuracy. The use of different resolution terrain models allowed for the analysis of the relationship between accuracy and optimal grid size. Additionally, a series of visibility predictions were made using Monte Carlo methods to add random error to the terrain elevation to estimate the probability of a targetâ s being visible. Finally, the LIDAR DSMs were used to determine the linear distance of terrain along the lines-of-sight between the observer and targets that were obscured by trees or bushes. A logistic regression was performed between that distance and the visibility of the target to determine the extent to which a greater amount of vegetation along the line-of-sight impacted the targetâ s visibility.<br>Master of Science
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Seymour, Michael S. "Refining low-quality digital elevation models using synthetic aperture radar interferometry." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0021/NQ46421.pdf.
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James, Timothy Douglas. "Error identification and correction methods for automatically derived digital elevation models." Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415623.
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Wonkovich, Mark A. "Evaluation of High-resolution Digital Elevation Models For Creating Inundation Maps." Bowling Green State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1167945221.
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Duldulao, Richard L. "Point density effects on digital elevation models generated from LiDAR data." Thesis, Monterey, Calif. : Naval Postgraduate School, 2009. http://handle.dtic.mil/100.2/ADA501602.
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Thesis (M.S. in Applied Physics)--Naval Postgraduate School, June 2009.<br>Thesis Advisor(s): Olsen, R. C. "June 2009." Description based on title screen as viewed on July 13, 2009. DTIC Identifiers: DEM (Digital Elevation Model), ILAP Bare Earth Extractor, Quick Terrain Modeler, LiDAR (Light Detection and Ranging). Author(s) subject terms: Digital Elevation Model, Point Density, LiDAR, QTM, Quick Terrain Modeler, ILAP Bare Earth Extractor, ENVI. Includes bibliographical references (p. 53-54). Also available in print.
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Li, Peng. "A vehicle-based laser system for generating high-resolution digital elevation models." Diss., Manhattan, Kan. : Kansas State University, 2010. http://hdl.handle.net/2097/3890.
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Zeilinger, Gerold, Maria Mutti, Manfred Strecker, Katrin Rehak, Bodo Bookhagen, and Marco Schwab. "Integration of digital elevation models and satellite images to investigate geological processes." Universität Potsdam, 2006. http://www.uni-potsdam.de/imaf/events/ge_work0602.html.
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In order to better understand the geological boundary conditions for ongoing or past surface processes geologists face two important questions: 1) How can we gain additional knowledge about geological processes by analyzing digital elevation models (DEM) and satellite images and 2) Do these efforts present a viable approach for more efficient research. Here, we will present case studies at a variety of scales and levels of resolution to illustrate how we can substantially complement and enhance classical geological approaches with remote sensing techniques.<br><br>
Commonly, satellite and DEM based studies are being used in a first step of assessing areas of geologic interest. While in the past the analysis of satellite imagery (e.g. Landsat TM) and aerial photographs was carried out to characterize the regional geologic characteristics, particularly structure and lithology, geologists have increasingly ventured into a process-oriented approach. This entails assessing structures and geomorphic features with a concept that includes active tectonics or tectonic activity on time scales relevant to humans. In addition, these efforts involve analyzing and quantifying the processes acting at the surface by integrating different remote sensing and topographic data (e.g. SRTM-DEM, SSM/I, GPS, Landsat 7 ETM, Aster, Ikonos…).
A combined structural and geomorphic study in the hyperarid Atacama desert demonstrates the use of satellite and digital elevation data for assessing geological structures formed by long-term (millions of years) feedback mechanisms between erosion and crustal bending (Zeilinger et al., 2005). The medium-term change of landscapes during hundred thousands to millions years in a more humid setting is shown in an example from southern Chile. Based on an analysis of rivers/watersheds combined with landscapes parameterization by using digital elevation models, the geomorphic evolution and change in drainage pattern in the coastal Cordillera can be quantified and put into the context of seismotectonic segmentation of a tectonically active region. This has far-reaching implications for earthquake rupture scenarios and hazard mitigation (K. Rehak, see poster on IMAF Workshop). Two examples illustrate short-term processes on decadal, centennial and millennial time scales: One study uses orogen scale precipitation gradients derived from remotely sensed passive microwave data (Bookhagen et al., 2005a). They demonstrate how debris flows were triggered as a response of slopes to abnormally strong rainfall in the interior parts of the Himalaya during intensified monsoons. The area of the orogen that receives high amounts of precipitation during intensified monsoons also constitutes numerous landslide deposits of up to 1km<sup>3</sup> volume that were generated during intensified monsoon phase at about 27 and 9 ka (Bookhagen et al., 2005b). Another project in the Swiss Alps compared sets of aerial photographs recorded in different years. By calculating high resolution surfaces the mass transport in a landslide could be reconstructed (M. Schwab, Universität Bern).<br><br>
All these examples, although representing only a short and limited selection of projects using remote sense data in geology, have as a common approach the goal to quantify geological processes. With increasing data resolution and new sensors future projects will even enable us to recognize more patterns and / or structures indicative of geological processes in tectonically active areas. This is crucial for the analysis of natural hazards like earthquakes, tsunamis and landslides, as well as those hazards that are related to climatic variability. The integration of remotely sensed data at different spatial and temporal scales with field observations becomes increasingly important. Many of presently highly populated places and increasingly utilized regions are subject to significant environmental pressure and often constitute areas of concentrated economic value. Combined remote sensing and ground-truthing in these regions is particularly important as geologic, seismicity and hydrologic data may be limited here due to the recency of infrastructural development. Monitoring ongoing processes and evaluating the remotely sensed data in terms of recurrence of events will greatly enhance our ability to assess and mitigate natural hazards.
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Interdisziplinäres Zentrum für Musterdynamik und Angewandte Fernerkundung<br>
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Pietro, Lisa S. "Developing terrestrial-LIDAR-based digital elevation models for monitoring beach nourishment performance." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 89 p, 2007. http://proquest.umi.com/pqdweb?did=1400424071&sid=10&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Spring, Ted. "Uncertainty comparison of Digital Elevation Models derived from different image file formats." Thesis, Högskolan i Gävle, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-17193.
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Unmanned Aerial Systems (UAS) have become increasingly popular recently for surveying and mapping because of their efficiency in acquiring remotely sensed data in a short amount of time and the low cost associated with them. They are used to generate digital elevation models (DEM) derived from aerial photography for various purposes such as the documentation of cultural heritage sites, archaeological surveying or earthwork volume calculations. This thesis investigates the possible effects different file formats may have on the quality of elevation models. In this thesis, an UAS survey was simulated using a digital camera to produce six DEMs based on JPEG, TIFF and RAW format in Agisoft Photoscan by taking two sets of images of a city model, in different light conditions. Furthermore, a reference DEM was produced in Geomagic Studio using data from a Leica Nova MS50 Multistation. The DEMs were then compared in Geomagic Control. The results from the 3D comparison in Geomagic Control show that the standard deviation of all elevation models is 4 mm with the exception of the elevation model derived from raw-edited images taken with lighting, which has a standard deviation of nearly 6 mm. Also, all of the models have an average deviation of 0.4 mm or less. The significant deviations in all DEMs occur in areas where the multistation lacked vision of certain objects of the city model such as walls, or on the edges of the analysed area. Additionally, the georeferencing results from Photoscan show that the DEMs based on normal light condition images have slightly lower georeferencing errors than the DEMs with lighting. It has been concluded that it is difficult to say whether file formats have any noticeably effect on the uncertainty of digital elevation models.
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Freitas, Henrique Rennó de Azeredo. "Drainage networks and watersheds delineation derived from TIN-based digital elevation models." Instituto Nacional de Pesquisas Espaciais (INPE), 2014. http://urlib.net/sid.inpe.br/plutao/2014/11.16.19.25.
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Digital Elevation Models (DEMs) are objects of great importance in many studies of natural sciences and one relevant area of their application is hydrology, as from a DEM it is possible to generate drainage networks and watersheds, which are essential elements in the understanding of hydrological processes. All the methods developed to generate drainage networks from a DEM depend on its representation and the most common representation is given by regular grids, where elevation values are assigned to cells uniformly distributed over space. However, this representation presents limitations in the flow directions, which are defined in only eight distinct directions. This work considers the terrain model given by a Triangulated Irregular Network (TIN) generated from contour lines and sampled points, where the terrain surface is modeled by several triangles defined from a set of points adequately distributed over space, so that the TIN can efficiently adapt to its irregularities. In addition, flow directions on TINs encompass a11 the possible directions and depend on the slope of the triangles, so this structure is more flexible regarding the calculation of water flows. The triangulation used in this work is the constrained Delaunay triangulation and the method that generates drainage networks considers flow directions given by the gradient of the plane defined from each triangle. Problems that commonly occur in DEMs such as flat areas and pits, which create inconsistencies in the terrain model and discontinuities in flows, also deserve special attention. In the present work, flat areas are removed by the insertion of new points into the triangulation with interpolated elevation values and pits by the definition of paths of points starting from the pit until reaching another point of lower elevation, where all these points have their elevation values re-interpolated. Most importantly, this work describes a methodology for calculating drainage paths from a TIN traced by processing the triangles with an associated priority and then connected defining a drainage graph structure, which is proposed in this work for the calculation of accumulated flows. Afterwards, drainage networks are generated according to given threshold values and watersheds are then delineated from the drainage networks. A11 the results from the TIN are qualitatively compared to regular grid results generated with the TerraHidro computational platform developed at INPE and also to an available drainage network produced by specialists and considered here as a reference of the main courses of water over the terrain. Results are very promising showing that TIN terrain models can be used to generate drainage networks from accumulated flows consistent with real-world hydrological patterns.<br>Modelos Digitais de Elevação (MDEs) são objetos de grande importância em muitos estudos das ciências naturais e uma área relevante de sua aplicação é a hidrologia, pois a partir de um MDE é possível gerar redes de drenagem e bacias hidrográficas, as quais são elementos essenciais no entendimento de processos hidrológicos. Todos os métodos desenvolvidos para gerar redes de drenagem a partir de um MDE dependem da sua representação e a representação mais comum é dada por grades regulares, onde valores de elevação são atribuídos em células uniformemente distribuídas no espaço. Entretanto, essa representação apresenta limitações nas direções de fluxo, as quais são definidas em apenas oito direções distintas. Este trabalho considera o modelo de terreno dado por uma Rede Triangular Irregular (Triangulated Irregular Network ou TIN) gerada de curvas de nível e pontos amestrados, onde a superfície do terreno é modelada por vários triângulos definidos a partir de um conjunto de pontos adequadamente distribuídos no espaço, de forma que o TIN pode eficientemente se adaptar as suas irregularidades. Além disso, direções de fluxo sobre TINs abrangem todas as direções possíveis e dependem da declividade dos triângulos, de modo que essa estrutura é mais flexível ao se considerar o cálculo dos fluxos de água. A triangulação utilizada neste trabalho é a triangulação de Delaunay restrita e o método que gera redes de drenagem considera direções de fluxo dadas pelo gradiente do plano definido por cada triângulo. Problemas que comumente ocorrem em MDEs tais como áreas planas e fossos, os quais criam inconsistências no modelo de terreno e descontinuidades nos fluxos, também merecem atenção especial. No presente trabalho, áreas planas são removidas pela inserção de novos pontos na triangulação com valores de elevação interpolados e fossos pela definição de caminhos de pontos iniciando do fosso até alcançar um outro ponto de menor elevação, onde todos esses pontos têm seus valores de elevação reinterpolados. Sobretudo, este trabalho descreve uma metodologia para calcular caminhos de drenagem a partir de um TIN traçados ao processar os triângulos com uma prioridade associada e depois conectados definindo uma estrutura de grafo de drenagem, a qual é proposta neste trabalho para o cálculo de fluxos acumulados. Posteriormente, redes de drenagem são geradas de acordo com determinado ti valores ele limiar e bacias hidrográficas são então delimitadas a partir das redes de drenagem. Todos os resultados do TIN são comparados qualitativamente a resultados de grade regular gerados com a plataforma computacional TerraHidro desenvolvida no INPE e também a uma rede de drenagem disponível, produzida por especialistas e considerada aqui como uma referência dos principais cursos d'água no terreno. Os resultados são bastante promissores mostrando que modelos de terreno TIN podem ser utilizados para gerar redes de drenagem a partir de fluxos acumulados consistentes com padrões hidrológicos reais.
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Lin, Yue. "A Comparison Study on Natural and Head/tail Breaks Involving Digital Elevation Models." Thesis, Högskolan i Gävle, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-15609.
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The most widely used classification method for statistical mapping is Jenks’s natural breaks. However, it has been found that natural breaks is not good at classifying data which have scaling property. Scaling property is ubiquitous in many societal and natural phenomena. It can be explained as there are far more smaller things than larger ones. For example, there are far more shorter streets than longer ones, far more smaller street blocks than bigger ones, and far more smaller cities than larger ones. Head/tail breaks is a new classification scheme that is designed for values that exhibit scaling property. In Digital Elevation Models (DEMs), there are far more lower elevation points than higher elevation points. This study performs both head/tail breaks and natural breaks for values from five resolutions of DEMs. The aim of this study is to examine advantages and disadvantages of head/tail breaks classification scheme compared with natural breaks. One of the five resolutions of DEMs is given as an example to illustrate the principle behind the head/tail breaks in the case study.The results of head/tail breaks for five resolutions are slightly different from each other in number of classes or level of details. The similar results of comparisons support the previous finding that head/tail breaks is advantaged over natural breaks in reflecting the hierarchy of data. But the number of classes could be reduced for better statistical mapping. Otherwise the top values, which are very little, would be nearly invisible in the map.A main conclusion to be drawn from this study is that head/tail breaks classification scheme is advantaged over natural breaks in presenting hierarchy or scaling of elevation data, with the top classes gathered into one. Another conclusion is when the resolution gets higher; the scaling property gets more striking.
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Fornaciai, Alessandro <1974>. "Morphometric Analysis of Mount Etna Lava Flows Using High Resolution Digital Elevation Models." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amsdottorato.unibo.it/7847/1/Alessandro_Fornaciai_Tesi.pdf.
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Morphometric analysis of lava flows provides crucial information for a better understanding of the processes of lava flow dynamics and emplacement. In this thesis, high-resolution DEMs obtained by the airborne LiDAR system and the UAV-SfM system are used for an extensive morphometric analysis of the Mount Etna (Italy) lava flow. A digital comparison of pre- and post-eruptive LiDAR DEMs of Etna was made to quantify the lava volumes emitted in the 2004-2005, 2005-2006 and 2007-2010 intervals. The erupted volume of 2004-2005 is ~63.3 × 106 m3 entirely emitted by the 2004-05 eruption. The erupted volume of 2005-2007 is ~ 42.0 × 106 m3, of which ~33.5 × 106 m3 emitted by the September-December 2006 eruption. The erupted volume of 2007-2010 is >86 × 106m3, most of which (~74 × 106m3) is formed by the lava flows of the 2008-2009 flank eruption. Lava flow morphometric analysis was performed over LiDAR DEM for eleven channel-fed lava flows through a semi-automatic procedure and using SVF and openness down parameters to better detect and delimit surface-specific elements, i.e. lava levees, base and channel-bed. The results show an inverse relation between slope and channel width, a certain coherence between average slope of levees and pre-emplacing slope, and the same trend between the channel width and channel-bed width. Finally, in order to investigate less costly methods for producing DEMs, we created a high-resolution DEM of the 1974 lava flow using the UAV-SfM system and then we compared it with the LiDAR-derived DEM. The UAV-SfM system can be effectively used to produce topographic data for large areas with an accuracy and resolution that are even higher than those of the LiDAR system. Therefore, the UAV-SfM system can be effectively used to update the topography of active volcanic areas with reasonable costs and short time of deployment.
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Dewez, Thomas Jean Bernard. "Geomorphic markers and digital elevation models as tools for tectonic geomorphology in central Greece." Thesis, Brunel University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272369.
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Gooch, Michael J. "Accuracy optimisation and error detection in automatically generated elevation models derived using digital photogrammetry." Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/7347.
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Users of current Digital Photogrammetric Systems (DPS) can now rapidly generate dense Digital Elevation Models (DEMs) with a minimal amount of training. This procedure is controlled through a set of strategy parameters embedded in the software. Previous research into the effect of these parameters on the resulting DEMs produc'ed mixed results, with some researchers finding that significant changes to the DEM can be made through manipulation of the parameters whilst others suggested that they have little effect. This thesis builds upon this early work to develop two systems that provide assistance for novice users. The first technique optimises the parameters with respect to DEM accuracy and takes the form of an expert system and compares the output from the DEM with a knowledge base to prescribe an improved set of parameters. The results suggest that the system works and can produce improvements in the accuracy of a DEM. It was found that in certain circumstances, changes to the parameters can have a significant effect on the resulting DEM, but this change does not occur across the entire DEM. The second aspect of the thesis details the development of a completely new approach that automatically detects low accuracy areas of the DEM and presents this information graphically. This is an important development since, as documented in the current literature, few quality control procedures are offered to users. The user can use this information to assist in the manual checking and editing of the final DEM, thus speeding up the workflow and improving the accuracy of the output. The results of tests (using the ERDAS Imagine OrthoMAX software) on a wide variety of imagery are presented and show that the technique reliably detects areas of a DEM with high errors. More significantly, the technique has also been tested on two other DPSs (Zeiss Phodis TS and VirtuoZo) and it was found that it worked well for the Zeiss system but could not be applied to the VirtuoZo software. This demonstrates that the research is not limited to the users of one software package and is of interest to the wider photogrammetric community.
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Mehrotra, Neeta. "An automated method for locating sinkholes in Montgomery County, Virginia, using digital elevation models." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-08222009-040435/.
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Tribe, Andrea S. "Automated recognition of valley heads, valley bottoms and drainage networks from grid digital elevation models." Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306257.
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Wang, Jianjun. "Modelling surface solar energy by use of landsat thematic mapper data and digital elevation models." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336667.
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Slabber, Frans Bresler. "Semi-automated extraction of structural orientation data from aerospace imagery combined with digital elevation models." Thesis, Rhodes University, 1996. http://hdl.handle.net/10962/d1005614.
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A computer-based method for determining the orientation of planar geological structures from remotely sensed images, utilizing digital geological images and digital elevation models (DEMs), is developed and assessed. The method relies on operator skill and experience to recognize geological structure traces on images, and then employs software routines (GEOSTRUC©) to calculate the orientation of selected structures. The operator selects three points on the trace of a planar geological feature as seen on a digital geological image that is co registered with a DEM of the same area. The orientation of the plane that contains the three points is determined using vector algebra equations. The program generates an ASCII data file which contains the orientation data as well as the geographical location of the measurements. This ASCII file can then be utilized in further analysis of the orientation data. The software development kit (SDK) for TNTmips v5.00, from MicroImages Inc. and operating in the X Windows environment, was employed to construct the software. The Watcom C\C++ Development Environment was used to generate the executable program, GEOSTRUC© . GEOSTRUC© was tested in two case studies. The case studies utilized digital data derived from the use of different techniques and from different sources which varied in scale and resolution. This was done to illustrate the versatility of the program and its application to a wide range of data types. On the whole, the results obtained using the GEOSTRUC© analyses compare favourably to field data from each test area. Use of the method to determine the orientation of axial planes in the case study revealed the usefulness of the method as a powerful analytic tool for use on a macroscopic scale. The method should not he applied in area with low variation in relief as the method proved to be less accurate in these areas. Advancements in imaging technology will serve to create images with better resolution, which will, in turn, improve the overall accuracy of the method.
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Smith, Nita Jane. "An ASTER Digital Elevation Model (DEM) for the Darwin-Hatherton Glacial System, Antarctica." Thesis, University of Canterbury. Geography, 2007. http://hdl.handle.net/10092/1480.
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The Darwin-Hatherton glacial system is an outlet glacial system in the Transantarctic Mountains, Antarctica, which drains ice from the East Antarctic Ice Sheet into the Ross Ice Shelf. This research provides remotely sensed data that can be used in modeling research for the Darwin-Hatherton glacial system, which in turn can be used in mass balance research for the West Antarctic Ice Sheet. Two improved digital elevation models (DEM) are produced to cover the lower Darwin Glacier and to cover the upper Darwin and Hatherton Glaciers. The new improved DEMs are generated from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite data, with a resolution of 45 m. To produce the two final DEMs, multiple DEMs are firstly adjusted to remove systematic errors and are then stacked and averaged to increase the accuracy and produce the final two DEMs. For the lower Darwin Glacier, 5 DEMs were averaged and in the upper Darwin and Hatherton Glaciers, 6 DEMs were averaged. The accuracy is quantified by a remaining error of + 9 m for the lower Darwin Glacier DEM and + 37 m for the upper Darwin and Hatherton Glaciers DEM. This is a significant improvement from the existing 200 m resolution Radarsat Antarctic mapping project (RAMPv2) DEM which has a remaining error of + 138 m over the lower Darwin Glacier and + 152 m over the upper Darwin and Hatherton Glaciers. The accuracy is assessed by comparing the ASTER and RAMPv2 DEMs to highly accurate ice, cloud and land elevation satellite (ICESat) laser altimetry data. A 15 m resolution, true colour, orthorectified image is provided for the entire Darwin-Hatherton glacial system from ASTER satellite imagery. The DEMs used to orthorectify the ASTER satellite imagery are the two new 45 m resolution ASTER DEMs. Lastly feature tracking was explored as a method for measuring surface ice velocity. This research shows that feature tracking is unsuitable for the Darwin-Hatherton glacial system if using 15 m resolution satellite imagery over a 1 to 4 year time period.
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Leitao, Joao Paulo Correia. "Enhancement of digital elevation models and overland flow path delineation methods for advanced urban flood modelling." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508782.
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The objective of this thesis is to improve existing and develop new DEM enhancement methods and DEM-based overland flow delineation methods in order to generate reliable overland flow networks. These networks can be used in conjunction with existing urban drainage modelling methodologies in order to improve surface flooding simulation results. The objective has been achieved by: developing new methods to merge DEMs; evaluating nad improving available DEM enhancement methods; improving methods to solve DEM flat area problems, and developing novel methods to improve overland flow path delineation. All improvements and new developments have been adapted to the specific characteristics of high-resolution DEMs and urban catchments. The experimental work undertaken in Lisbon, together with two case-studies in the UK, was used to validate the concepts proposed in this thesis. It is concluded that DEM enhancement methods can be used to improve DEMs for overland flow delineation, thereby enhancing the reliability of urban flood modelling. The advanced flow path delineation methods developed here produce more reliable results than conventional overland flow path delineation methods. The hydraulic simulation results obtained confirm the advantages of applying 1D/1D modelling to simulate urban flood events. However, the findings show that the use of these methods needs to be preceded by a thorough analysis and quantification of Dem surface characteristics, and by a detailed calibration and validation procedure. Independent testing carried out by UKWIR has proved the adequacy and reliability of the developed methodology in full scale flood risk mapping applications.
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Srivastava, Anurag. "Comparison of Two Algorithms for Removing Depressions and Delineating Flow Networks From Grid Digital Elevation Models." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/34268.
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Digital elevation models (DEMs) and their derivatives such as slope, flow direction and flow accumulation maps, are used frequently as inputs to hydrologic and nonpoint source modeling. The depressions which are frequently present in DEMs may represent the actual topography, but are often the result of errors. Creating a depression-free surface is commonly required prior to deriving flow direction, flow accumulation, flow network, and watershed boundary maps. The objectives of this study were: 1) characterize the occurrence of depressions in 30m USGS DEMs and assess correlations to watershed topographic characteristics, and 2) compare the performance of two algorithms used to remove depressions and delineate flow networks from DEMs.
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Sixty-six watersheds were selected to represent a range of topographic conditions characteristic of the Piedmont and Mountain and Valley regions of Virginia. Analysis was based on USGS 30m DEMs with elevations in integer meters. With few exceptions watersheds fell on single 7.5minute USGS quadrangle sheets, ranged in size from 450 to 3000 hectares, and had average slopes ranging from 3 to 20 percent. ArcView (3.1) with the Spatial Analyst (1.1) extension was used to summarize characteristics of each watershed including slope, elevation range, elevation standard deviation, curvature, channel slope, and drainage density. TOPAZ (ver 1.2) and ArcView were each used to generate a depression-free surface, flow network and watershed area. Characteristics of the areas 'cut' and 'filled' by the algorithms were compared to topographic characteristics of the watersheds. Blue line streams were digitized from scanned USGS 7.5minute topographic maps (DRGs) then rasterized at 30 m for analysis of distance from the derived flow networks.
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The removal of depressions resulted in changes in elevation values in 0 - 11% of the cells in the watersheds. The percentage of area changed was higher in flatter watersheds. Changed elevation cells resulted in changes in two to three times as many cells in derivative flow direction, flow accumulation and slope grids. Mean fill depth by watershed ranged from 0 to 10 m, with maximum fill depths up to 40 m. In comparison with ArcView, TOPAZ, on average affected 30% fewer cells with less change in elevation. The significance of the difference between ArcView and TOPAZ decreased as watershed slope increased. A spatial assessment of the modified elevation and slope cells showed that depressions in the DEMs occur predominantly on or along the flow network. Flow networks derived by ArcView and TOPAZ were not significantly different from blue line streams digitized from the USGS quadrangles as indicated by a paired t test. Watershed area delineated by ArcView and TOPAZ was different for almost all watersheds, but was generally within 1%.
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Conclusions from this study are: 1) The depressions in 30 m DEMs can make up a significant portion of the area especially for flatter watersheds; 2) The TOPAZ algorithm performed better than ArcView in minimizing the area modified in the process of creating a depressionless surface, particularly in flatter topography; 3) Areas affected by removing depressions are predominantly adjacent to the stream network; 4) For every elevation cell changed, slopes are changed for two to three cells, on average; and 5) ArcView and TOPAZ derived flow networks closely matched the blue line streams.<br>Master of Science
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Zutautas, Vaidutis. "Charcoal Kiln Detection from LiDAR-derived Digital Elevation Models Combining Morphometric Classification and Image Processing Techniques." Thesis, Högskolan i Gävle, Samhällsbyggnad, GIS, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-24374.
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This paper describes a unique method for the semi-automatic detection of historic charcoal production sites in LiDAR-derived digital elevation models. Intensified iron production in the early 17th century has remarkably influenced ways of how the land in Sweden was managed. Today, the abundance of charcoal kilns embedded in the landscape survives as cultural heritage monuments that testify about the scale forest management for charcoal production has contributed to the uprising iron manufacturing industry. An arbitrary selected study area (54 km2) south west of Gävle city served as an ideal testing ground, which is known to consist of already registered as well as unsurveyed charcoal kiln sites. The proposed approach encompasses combined morphometric classification methods being subjected to analytical image processing, where an image that represents refined terrain morphology was segmented and further followed by Hough Circle transfer function applied in seeking to detect circular shapes that represent charcoal kilns. Sites that have been identified manually and using the proposed method were only verified within an additionally established smaller validation area (6 km2). The resulting outcome accuracy was measured by calculating harmonic mean of precision and recall (F1-Score). Along with indication of previously undiscovered site locations, the proposed method showed relatively high score in recognising already registered sites after post-processing filtering. In spite of required continual fine-tuning, the described method can considerably facilitate mapping and overall management of cultural resources.
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Bhadra, Sourav. "Assessing the Impacts of Anthropogenic Drainage Structures on Hydrologic Connectivity Using High-Resolution Digital Elevation Models." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2573.
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Stream flowline delineation from high-resolution digital elevation models (HRDEMs) can be problematic due to the fine representation of terrain features as well as anthropogenic drainage structures (e.g., bridges, culverts) within the grid surface. The anthropogenic drainage structures (ADS) may create digital dams while delineating stream flowlines from HRDEMs. The study assessed the effects of ADS locations, spatial resolution (ranged from 1m to 10m), depression processing methods, and flow direction algorithms (D8, D-Infinity, and MFD-md) on hydrologic connectivity through digital dams using HRDEMs in Nebraska. The assessment was conducted based on the offset distances between modeled stream flowlines and original ADS locations using kernel density estimation (KDE) and calculated frequency of ADS samples within offset distances. Three major depression processing techniques (i.e., depression filling, stream breaching, and stream burning) were considered for this study. Finally, an automated method, constrained burning was proposed for HRDEMs which utilizes ancillary datasets to create underneath stream crossings at possible ADS locations and perform DEM reconditioning. The results suggest that coarser resolution DEMs with depression filling and breaching can produce better hydrologic connectivity through ADS compared with finer resolution DEMs with different flow direction algorithms. It was also found that stream burning with known stream crossings at ADS locations outperformed depression filling and breaching techniques for HRDEMs in terms of hydrologic connectivity. The flow direction algorithms combining with depression filling and breaching techniques do not have significant effects on the hydrologic connectivity of modeled stream flowlines. However, for stream burning methods, D8 was found as the best performing flow direction algorithm in HRDEMs with statistical significance. The stream flowlines delineated using the proposed constrained burning method from the HRDEM was found better than depression filling and breaching techniques. This method has an overall accuracy of 78.82% in detecting possible ADS locations within the study area.
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Charrier, Richard Li Yingkui. "Assessing the resolution effects of digital elevation models on automated floodplain delineation a case study from the Camp Creek Watershed in Missouri /." Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/5337.
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The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on December 21, 2009). Thesis advisor: Dr. Yingkui (Philip) Li. Includes bibliographical references.
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Reynolds, James Robb. "Using digital elevation models to measure the surface and volumetric change of Athabasca Glacier, Canada, 1919-1979." Waterloo, Ontario : Wilfrid Laurier University, 1996. http://wwwlib.umi.com/cr/wlu/fullcit?pMM11455.
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Thesis (M.A.)-Wilfrid Laurier University, 1996.<br>Includes bibliographical references (l.174-182). Issued also online via the World Wide Web; files in PDF format available to WLU users. Available in microfiche format.
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Bundela, Devendra Singh. "Influence of digital elevation models derived from remote sensing on spatio-temporal modelling of hydrologic and erosion processes." Thesis, Cranfield University, 2004. http://hdl.handle.net/1826/796.
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LISEM, a physically-based distributed and dynamic erosion model within the PCRaster GIS, is used to investigate the influence of different spatial representations of input parameters on surface hydrologic and erosion processes at three antecedent soil moisture levels for a 6-hour heavy storm at catchment scale.
Two derived DEMs viz. Cartometric and PulSAR DEMs and three public domain DEMs viz. Landmap, ASTER and SRTM were used in this study. These five DEMs of various original resolutions along with a land use and land cover map and a soil map of the Saltdean catchment were resampled into five spatial representations at 20, 40, 60, 80 and 100 m grid-cell sizes to create input parameters at each resolution. Spaceborne radar interferometry was investigated for generating a suitable DEM for modelling in the context of developing countries having poor availability of quality DEMs. The land use and land cover map was derived from SPOT-1 data and the infiltration parameters were estimated from the 1:250 000 soil map using pedotransfer functions. Crop, soil and soil surface parameters were estimated for possible field conditions in the catchment. Subsequently, twenty-five LISEM databases of 30 input parameters each were created in PCRaster and tested in the model.
The results show that at increasing the grid-cell size of a DEM, the slope gradient flattens and the drainage length shortens. Both of these have competing effects on runoff and sediment flow routing. The catchment area also increases at larger grid-cell sizes and influences these processes, which are then normalised for the comparison of various resolution results.
In the absence of observed runoff and average soil loss data, a relative evaluation across resolutions and DEMs was carried out in the context of developing countries. The results indicate that the PulSAR and Landmap DEMs have higher variations in runoff and average soil loss than the ASTER DEM, Cartometric DEM, and SRTM DEM at coarser resolutions at all three moisture levels with respect to their result at 20 m. The SRTM DEM has lower variability than other DEMs at finer resolutions. It is demonstrated that resampling a medium resolution SRTM DEM at smaller grid-cell sizes does not improve the prediction of runoff and soil erosion. At 100 m resolution, the runoff is over predicted as compared to an 80 m resolution. Hence, high resolution DEMs should be resampled to 80 m grid-cell size, but the resampling reduces the spatial variability drastically.
The results also indicate that the prediction of runoff is improved for the PulSAR DEM and Landmap DEM, and is slightly improved for the ASTER DEM as compared to the Cartometric DEM, but it is not improved for the SRTM DEM. It is related with their slope gradients.
The results support that the average soil loss is improved for the PulSAR DEM and Landmap DEM and is slightly degraded for the SRTM DEM as compared to the Cartometric DEM. It also suggests that both are suitable for erosion prediction due to higher slope gradient mapped by remote sensing. The ASTER DEM did not produce reliable soil losses at all the moisture levels. Therefore, it should not be used for the prediction of soil erosion.
The results also indicate that small grid-cell size produces detailed soil erosion and deposition outputs, which help in identifying the exact location of sediment source and sink areas necessary for planning the effective conservation strategy in the catchment.
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Wang, Daming Biological Earth & Environmental Sciences Faculty of Science UNSW. "Morphometric characteristisaiton of landform from DEMs." Publisher:University of New South Wales. Biological, Earth & Environmental Sciences, 2008. http://handle.unsw.edu.au/1959.4/43326.
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Digital Elevation Models (DEMs) are fundamental datasets for environmental modelling. They provide the basic data from which terrain indices that represent or influence environmental phenomena are derived, for example slope gradient and hydrological contributing area, and also the source from which specific morphometric features are quantified and characterised, for example mountains and drainage basins. This thesis focuses on the latter, with the aim being to develop an algorithm to characterise the landscape in terms of five morphometric features (peaks, passes, pits, ridges and valleys) and to assess its validity and effectiveness for characterising landform from DEMs. The research in this thesis is divided into two parts. First, an algorithm of morphometric characterisation of landform from OEMs is developed based on a locally fitted quadratic surface and its positional relationship with the analysis window. Five requirements are taken into account within the algorithm: (1) the ideal cases of different morphometric features are simply and clearly defined; (2) the output is spatially continuous to reflect the inherent fuzziness of landform features; (3) the output is easily combined into a multi-scale index across a range of operational scales; (4) the standard general morphometric parameters can be easily quantified due to the easy calculation of first and second order derivatives from the quadratic surface; and (5) the algorithm is applicable to the different data structures used to represent DEMs. An additional benefit of the quadratic surface is the derivation of the R?? goodness-of-fit statistic, which allows both an assessment of the reliability of the results and the complexity of the terrain. Of the five morphometric features identified using the algorithm, valleys are perhaps the most commonly used. Therefore the second part of this thesis is a more detailed comparison between the Multi-Scale Valleyness (MSV) and three existing algorithms (D8, D∞ and MrVBF). D8 and D∞ are global flow accumulation algorithms, and perform well when characterising valley centre lines. However, they do not identify the valley areas themselves, although this is to be expected given their formulation. MrVBF focuses on characterising valley bottoms and so performs well when characterising valleys in broad and topographically flat areas. It does not identify valleys in the steeper upland parts of a catchment, although this too is something to be expected given its formulation. MSV directly characterises valley areas from a geomorphometric point of view, and performs well for both upland and lowland catchments, irrespective of their width. Overall, the results show that the single- and multi-scale terrain indices developed in this research perform well when characterising the five morphometric features. The approach has considerable potential for use in environmental modelling and terrain analysis.
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Bater, Christopher William. "Assessing indicators of forest sustainability using lidar remote sensing." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/599.
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The Province of British Columbia is developing a suite of attributes to assess and monitor forest sustainability. Each attribute is in turn evaluated using a variety of indicators. Recently, digital remote sensing technologies have emerged as both alternative and supplement to traditional monitoring techniques, with light detection and ranging (lidar) in particular showing great promise for estimating a variety of indicators. The goal of this thesis was to review and assess the ability of lidar to estimate selected indicators of forest sustainability. Specifically, digital elevation model (DEM) interpolation (from which indicators are extracted both directly and indirectly) and wildlife tree class distributions were examined.
Digital elevation models are a key derivative of lidar data, and their generation is a critical step in the data processing stream. A validation exercise was undertaken to determine which combination of interpolation routine and spatial resolution was the most accurate. Ground returns were randomly subsetted into prediction and validation datasets. Linear, quintic, natural neighbour, spline with tension, regularized spline, inverse distance weighting, and ANUDEM interpolation routines were used to generate surfaces at spatial resolutions of 0.5, 1.0, and 1.5 m. The 0.5 m natural neighbour surface was found to be the most accurate (RMSE=0.17 m). Classification and regression tree analysis indicated that slope and ground return density were the best predictors of interpolation error.
The amount and variability of living and dead wood in a forest stand is an important indicator of forest biodiversity. In the second study, the capacity of lidar to estimate the distribution of living and dead trees within forests is investigated. Twenty-two field plots were established in which each stem (DBH>10cm) was assigned to a wildlife tree (WT) class. For each plot, a suite of lidar-derived predictor variables were extracted. Ordinal logistic regression was then employed to predict the cumulative proportions of stems within the WT classes. Results indicated that the coefficient of variation of the lidar height data was the best predictor variable (r = 0.85, p <0.000, RMSE = 4.9%). The derived relationships allowed for the prediction of the proportion of stems within WT classes across the landscape.
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Smeda, Braden William. "Area and Volume Changes of Adams Icefield from 1948 to 2019, Axel Heiberg Island, Nunavut, Canada." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/41602.
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There has been a marked increase in melt season length over the past two decades on glaciers and ice caps within Canada’s Queen Elizabeth Islands (QEI). Prior to the year ~2000 land ice was in a state of slightly negative mass balance (-11 +/- 11.5 Gt yr⁻¹ over 1958-1995), but recent GRACE measurements suggest that mass losses averaged -33 +/- 5 Gt yr⁻¹ between 2003-2015. These losses have primarily been attributed to meltwater runoff, making the QEI one of the largest recent contributors to sea level rise outside of the ice sheets. Despite these losses, there is a lack of information concerning how a warming climate is affecting small (<1 km²) ice bodies, which are considered sensitive indicators of change due to their short response time.
In this study, historical and contemporary aerial photographs, high resolution optical satellite imagery, and ground penetrating radar (GPR) surveys are used to determine area, thickness, mass and volume changes of Adams Icefield within Expedition Fiord, Axel Heiberg Island, Nunavut, over the past seven decades (1948/59-2019). Area changes are determined from a comparison of air photos acquired in 1948/59 with satellite images acquired since 1979. Contemporary (2001, 2012, 2019) digital elevation models (DEMs) were either collected or created from stereo satellite images, and via aerial photo surveys using Structure from Motion photogrammetry. DEM of Difference maps calculated from these DEMs provide volume and mass changes. Results illustrate a steady reduction in glacier area, thickness, and volume prior to the year ~2000, followed by a rapid increase in losses over the past two decades. As a result, Adams Icefield is now rapidly declining and is likely to completely disappear early in the twenty-second century.
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Bates, Jeffrey Kenneth. "An evaluation of digital elevation models and geotechnical properties of the glacial deposits in Franklin County, Ohio, using a geographic information system." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1189559602.
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Predoehl, Andrew. "A Statistical Model of Recreational Trails." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/612599.
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We present a statistical model of recreational trails, and a method to infer trail routes from geophysical data, namely aerial imagery and terrain elevation. We learn a set of textures (textons) that characterize the imagery, and use the textons to segment each image into super-pixels. We also model each texton's probability of generating trail pixels, and the direction of such trails. From terrain elevation, we model the magnitude and direction of terrain gradient on-trail and off-trail. These models lead to a likelihood function for image and elevation. Consistent with Bayesian reasoning, we combine the likelihood with a prior model of trail length and smoothness, yielding a posterior distribution for trails, given an image. We search for good values of this posterior using both a novel stochastic variation of Dijkstra's algorithm, and an MCMC-inspired sampler. Our experiments, on trail images and groundtruth collected in the western continental USA, show substantial improvement over those of the previous best trail-finding methods.
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Ok, Ali Ozgun. "Accuracy Assessment Of The Dem And Orthoimage Generated From Aster." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606588/index.pdf.
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In this study, DEMs and orthoimages were generated from ASTER imagery and their accuracies were assessed. The study site covers an area of approximately 60 x 60 km and encloses the city of Ankara.
First, DEMs were generated from stereo ASTER images. In order to find the best GCP combination, different number of GCPs (8, 16, 24, and 32) was used. The accuracies of the generated DEMs were then assessed based on the check points (CP), slopes and land cover types. It was found that 16 GCPs were good compromise to produce the most accurate DEM. The post processing and blunder removal increased the overall accuracy up to 38%. It was also found that there is a strong linear relationship between the accuracies of DEMs and the slopes of the terrain. The accuracies computed for water, urban, forest, mountainous, and other areas were found to be 5.01 m, 8.03 m, 12.69 m, 17.14 m, and 10.21 m, respectively. The overall accuracy was computed as 10.92 m.
The orthorectification of the ASTER image was carried out using 12 different mathematical models. Based on the results, the models First Order 2D Polynomial, Direct Linear Transformation and First Order Polynomial with Relief have produced the worst results. On the other hand, the model Second Order Rational Function appears to be the best model to orthorectify the ASTER images. However, the developed model Second Order Polynomial with Relief provides simplicity, consistency and requires less number of GCPs when compared to the model Second Order Rational Function.
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Niemann, Rafaela Soares [UNESP]. "Comparação de métodos de filtragem e geração de modelos digitais de terreno a partir de imagens obtidas por veículo aéreo não-tripulado." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/152635.
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Previous issue date: 2017-12-07<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>Os modelos digitais de elevação são importantes para a geração de informações sobre variáveis ambientais correlacionadas à topografia, principalmente como subsídio à análises geomorfométricas. O sensoriamento remoto pode contribuir com a geração de modelos digitais de elevação, principalmente através do uso de sensores de alta resolução espacial e tecnologias avançadas. Os VANTs – Veículos Aéreos Não Tripulados – tem sido cada vez mais explorados no âmbito da cartografia e topografia, com atuação cada vez mais importante dentro da ciência, devido à capacidade de transportarem diferentes sensores e ao seu baixo custo de operação. Câmeras fotográficas simples acopladas aos VANTs podem ser combinadas com tecnologias de visão computacional, trazendo novas oportunidades para explorar a geração de modelos digitais de elevação. Algoritmos de visão computacional, como o Structure-from-Motion (SfM), permitem a extração de pontos tridimensionais a partir de imagens sobrepostas obtidas por VANTs. Esses pontos compõem nuvens de pontos capazes de subsidiar a geração de modelos digitais de superfície (MDS), quando combinadas com algoritmos de interpolação de dados. Contudo, os modelos gerados desta maneira nos retornam informações relacionadas à superfície dos objetos presentes sobre o terreno, incluindo por exemplo construções e dosséis vegetais. A filtragem e classificação das nuvens de pontos se faz assim necessária para geração de modelos digitais que descrevam mais fielmente a superfície do terreno, sem estes elementos. Nesta dissertação, avaliamos dois métodos para a filtragem e interpolação de modelos digitais de terreno (MDT) a partir de nuvens de pontos geradas por imageamento ótico baseado em VANTs. A área de estudo escolhida foi a região da Serra do Cipó-MG, caracterizada por relevo acidentado e cobertura vegetal variada. O primeiro método consistiu na filtragem (classificação) direta da nuvem de pontos, e o segundo na filtragem do modelo digital de superfície em formato raster, ambos seguidos de interpolação. Os métodos avaliados se mostraram adequados, com coeficientes de determinação da ordem de R² = 0,98 em relação a dados de referência tomados por DGPS. A filtragem foi bastante eficiente para áreas íngremes e com vegetação baixa, e menos eficiente em áreas de vegetação arbórea densa. Os métodos avaliados no presente trabalho contribuirão para a melhoria da geração de MDTs com base na tecnologia emergente oferecida pelos VANTs, que poderão ser utilizados como subsídios a estudos ambientais diversos.<br>Digital elevation models are important for producing information on different environmental variables correlated to topography, especially for geomorphometric analyses. Remote sensing can contribute to the generation of digital elevation models, mainly through high spatial resolution sensors and advanced technologies. UAVs - Unmanned Aerial Vehicles - have been increasingly employed in the fields of cartography and topography, and have had an increasingly prominent role in science, as they can carry different sensors and have low-cost operation. Simple cameras attached to UAVs can be combined with computer vision technologies, bringing new opportunities to explore the production of digital elevation models. Computer vision algorithms such as Structure-from-Motion (SfM) allow the extraction of threedimensional points from superimposed images obtained by UAVs. These points make up points clouds capable of supporting the production of digital surface models (DSM) when combined with interpolation algorithms. However, models generated this way give us information related to the surface of objects present on the ground, including buildings and plant canopies. Point cloud filtering and classification is thus necessary for producing digital models that more accurately describe the bare terrain surface. In this dissertation, we evaluated two methods for filtering and interpolating digital terrain models (DTM) from point clouds generated by UAVbased optical imaging. The chosen study area was the Serra do Cipó region (Minas Gerais, Brazil), characterized by rugged relief and heterogeneous vegetation cover. The first method consisted of direct filtering (classification) of the point cloud, and the second method was based on filtering the digital surface model in raster format, both followed by interpolation. The evaluated methods were adequate, with determination coefficients of the order of R² = 0.98 in relation to reference data taken by DGPS. Filtering was quite efficient for steep areas with low vegetation, and less efficient in areas of dense arboreal vegetation. The methods evaluated in the present work will contribute to the improvement and generation of DTMs based on the emerging technology offered by UAVs, which can be used as subsidies to diverse environmental studies.
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Cavazzi, Stefano. "Spatial scale analysis of landscape processes for digital soil mapping in Ireland." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/8591.
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Soil is one of the most precious resources on Earth because of its role in storing and recycling water and nutrients essential for life, providing a variety of ecosystem services. This vulnerable resource is at risk from degradation by erosion, salinity, contamination and other effects of mismanagement. Information from soil is therefore crucial for its sustainable management. While the demand for soil information is growing, the quantity of data collected in the field is reducing due to financial constraints. Digital Soil Mapping (DSM) supports the creation of geographically referenced soil databases generated by using field observations or legacy data coupled, through quantitative relationships, with environmental covariates. This enables the creation of soil maps at unexplored locations at reduced costs. The selection of an optimal scale for environmental covariates is still an unsolved issue affecting the accuracy of DSM. The overall aim of this research was to explore the effect of spatial scale alterations of environmental covariates in DSM. Three main targets were identified: assessing the impact of spatial scale alterations on classifying soil taxonomic units; investigating existing approaches from related scientific fields for the detection of scale patterns and finally enabling practitioners to find a suitable scale for environmental covariates by developing a new methodology for spatial scale analysis in DSM. Three study areas, covered by detailed reconnaissance soil survey, were identified in the Republic of Ireland. Their different pedological and geomorphological characteristics allowed to test scale behaviours across the spectrum of conditions present in the Irish landscape. The investigation started by examining the effects of scale alteration of the finest resolution environmental covariate, the Digital Elevation Model (DEM), on the classification of soil taxonomic units. Empirical approaches from related scientific fields were subsequently selected from the literature, applied to the study areas and compared with the experimental methodology. Wavelet analysis was also employed to decompose the DEMs into a series of independent components at varying scales and then used in DSM analysis of soil taxonomic units. Finally, a new multiscale methodology was developed and evaluated against the previously presented experimental results. The results obtained by the experimental methodology have proved the significant role of scale alterations in the classification accuracy of soil taxonomic units, challenging the common practice of using the finest available resolution of DEM in DSM analysis. The set of eight empirical approaches selected in the literature have been proved to have a detrimental effect on the selection of an optimal DEM scale for DSM applications. Wavelet analysis was shown effective in removing DEM sources of variation, increasing DSM model performance by spatially decomposing the DEM. Finally, my main contribution to knowledge has been developing a new multiscale methodology for DSM applications by combining a DEM segmentation technique performed by k-means clustering of local variograms parameters calculated in a moving window with an experimental methodology altering DEM scales. The newly developed multiscale methodology offers a way to significantly improve classification accuracy of soil taxonomic units in DSM. In conclusion, this research has shown that spatial scale analysis of environmental covariates significantly enhances the practice of DSM, improving overall classification accuracy of soil taxonomic units. The newly developed multiscale methodology can be successfully integrated in current DSM analysis of soil taxonomic units performed with data mining techniques, so advancing the practice of soil mapping. The future of DSM, as it successfully progresses from the early pioneering years into an established discipline, will have to include scale and in particular multiscale investigations in its methodology. DSM will have to move from a methodology of spatial data with scale to a spatial scale methodology. It is now time to consider scale as a key soil and modelling attribute in DSM.
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Muirhead, Fiona. "Exploiting sparsity for persistent scatterer detection to aid X-band airborne SAR tomography." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28880.
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This thesis evaluates the potential for using line of sight returns and return signals from underneath a forest canopy using X-band, airborne synthetic aperture radar (SAR) tomography. Approximately 30% of the Earth’s land surface is covered by vegetation, therefore global digital elevation models (DEMs) contain a signal from the forest canopy and not the ground. By uncovering new techniques to find the ground signals, using data collected from airborne platforms as verification, such procedures could be applied to currently operational and future X-band, spaceborne systems with the aim of resolving much of the vegetation bias on an international scale. Data from three sources is presented; data collected from Selex ES’s SAR systems, the GOTCHA dataset and simulated data. Before carrying out tomography it is shown that SAR interferometry (InSAR) can successfully be applied to X-band, helicopter data. A scatterer defined as a candidate persistent scatterer (CPS) is introduced, where the pixels are stable and coherent over a matter of days. An algorithm for selecting CPSs is developed by exploiting sparsity and a novel choice of hard thresholding operator. Using simulated forestry and SAR information the effects of changing input parameters on the outcome of the tomographic profile is analysed. What is found in this study is that model simulations demonstrate that ground points can be detected if the platform motion is relatively stable and that temporal decorrelation over the forest volume is kept to a minimal. An understory can confuse the tomographic profile since less line of sight observations can be made. By combining line of sight observations alongside new tomography techniques on high resolution SAR data this thesis shows it is possible to detect ground scatterers, even at X-band.
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Thompson, Grant. "Effects of DEM resolution on GIS-based solar radiation model output: A comparison with the National Solar Radiation Database." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1258663688.
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Moon, Peter Olaf. "An investigation into the design of a satellite based stereo imaging sensor and the use of automatic image matching in the production of digital elevation models." Master's thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/8462.
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Bibliography: leaves 106-110.<br>Two problems are addressed in this dissertation. They are the design of a micro-satellite based stereo imaging sensor and the automatic matching of digital stereo images for automatic cartography applications. The two problems are related; they are both components of a stereo vision system. The research was initially motivated by the decision of the Department of Electrical and Electronic Engineering of the University of Stellenbosch to develop and build an experimental micro-satellite, SUNSAT. The proposed payload included a high resolution multi-spectral stereo imaging sensor. The second problem was motivated by the desire to use an automatic matching system to process the images produced by the sensor. The investigation, into the sensor design, was divided into two parts. The first part investigated the feasibility of the sensor and the second part dealt with the development of a design specification. The investigation, into automatic matching, dealt with the degree to which a set of requirements could be met. These requirements relate to the accuracy, reliability, generality, predictability and complexity of the matching system. The effect of scene characteristics was also investigated. The results showed that it is possible to build a micro-satellite based stereo imaging sensor. The recommended sensor design included three spectral bands, an 8 bit analogue-to-digital converter and a focal length of 535 mm. Furthermore, it was found that a sub-pixel accuracy matching requirement can be met and that a matching reliability of 89.6 can be achieved. Finally, it was found that the best matching results are obtained in areas of high image variance and low disparity variance.
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Ryherd, Julia Kay. "QUANTIFYING THE RATES AND SPATIAL DISTRIBUTION OF RECENT SEDIMENTATION WITHIN THE HYDROLOGICALLY CONNECTED FLOODPLAINS OF THE MIDDLE MISSISSIPPI RIVER, USA, USING DIGITAL ELEVATION MODELS AND DENDROGEOMORPHOLOGY." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2189.
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The construction of levees along the Mississippi River [MR], beginning in the mid-to-late nineteenth century, have isolated the river along many segments from its floodplain. Sediment from the river is currently deposited in the hydrologically connected floodplain [HCF], the area between the channel margin at low water and the levees. Researchers have studied the amount and rates of sediment deposition along the Upper and Lower Mississippi River segments from the headwaters to Pool 22 and from the Ohio River to the delta; however, no such assessments have been undertaken along the Middle Mississippi River [MMR]. This study attempts to fill the knowledge gap by assessing sedimentation along three islands within the Middle Mississippi River National Wildlife Refuge. On these islands two approaches were undertaken to assess sedimentation along the MMR’s HCF: dendrogeomorphology and the DEM of Difference [DoD] approach. The dendrogeomorphic approach uses tree-ring analyses to document and interpret geomorphic processes and the rates at which they are occurring. The DoD approach subtracts an older DEM from a newer DEM in order to see the change in elevation/depth over time. The geomorphology of the islands and then the entire MMR HCF (from the confluence of the Missouri River to Thebes, IL) were mapped. Using the sedimentation rates for the geomorphic landforms from the three study islands, the sedimentation rates and volumes for the aforementioned portion of the MMR’s HCF were estimated. The estimated volume of sediment was then compared to the MMR’s suspended sediment flux to determine how much of the suspended sediment was going into storage within the MMR’s HCF. The dendrogeomorphic and DoD methods for the study islands yielded average sedimentation rates of 13.3-16.9 mm year-1 and 21.5-80.1 mm year-1, respectively. The rates for the individual landforms on the islands using the dendrogeomorphic results ranged from 5.2 mm year-1 for the splay to 21.8 mm year-1 for the natural levee and splay, with a weighted average of 16.6 mm year-1 for the MMR HCF. Using these rates and the likely range of densities for the floodplain sediments, it is estimated that 4.9-6.6 million metric tons of sediment is accumulating within the MMR annually. This is approximately 5.4-7.4% of the average annual suspended sediment load of the Mississippi River at St. Louis. This means that the MMR is a major sediment sink. If these relatively rapid rates of deposition continue, they have the potential to substantially reduce the HCF’s ability to convey and store flood water which will result in increased flood levels and, consequently, flood risk within the MMR’s levee protected floodplain in the coming decades.
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Bueno, Jean Michel Moura. "Modelos digitais de elevação e predição do carbono orgânico do solo no planalto do Estado do Rio Grande do Sul." Universidade Federal de Santa Maria, 2014. http://repositorio.ufsm.br/handle/1/5613.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>The requirement for quantitative soil information has increased as a consequence of the global scenarios. The digital soil mapping (DSM) seeks to produce consistent data with the current needs through the generation of functional soil maps in multi-scales. The aim of this study was to evaluate the altimetry quality and limitations of digital elevation model (DEM) in order to assist in choosing the most suitable DEM to derive terrain attributes (TA) to develop spatial prediction functions to be applied to digital mapping of soil organic carbon (SOC) of farm scale in the Plateau of the state of Rio Grande do Sul (RS). The study was conducted on a 937 ha area located in the municipality of Giruá, RS, Brazil. They collected 243 sampling points in the 0-5 cm layer and an accomplished planialtimetric survey (PS) considered in this study the truth of the ground of altitude values. DEM evaluated were: DEM-PS (generated from the PS), DEM-LETTER (generated by interpolating the level of topographic map curves), DEM-ASTER, DEM- SRTM and DEM-TOPODATA. The DEM were evaluated for precision altimetry through statistical test value of the square root of the mean square error (RMSE) and application of the Brazilian Cartographic Standard for defining the scale of each DEM based on the accuracy of the altitude. TA derived from each DEM were faced with the AT derived from the DEM-PS. The results showed that the DEM-PS presented the best quality of elevation data (RMSE = 1.93 m), followed by DEM-SRTM (RMSE = 5.95 m), DEM- (RMSE = 8.28 m), DEM-TOPODATA (RMSE = 9.78 m) and DEM-ASTER (RMSE = 15.57 m). The size of the area and gently rolling relief were the main factors that influenced the results. The DEM-PS is suited in scale 1: 10,000 Class D, while DEM-LETTER and DEM-SRTM are suited in scale 1: 50,000 class B, the DEM-TOPODATA the scale 1: 50,000 class D and the DEM-ASTER scale 1: 100,000 Class B. With regard to TA, the DEM-SRTM and DEM-TOPODATA present results closer to the DEM-PS and smaller RMSE values for each TA assessed. The prediction function constructed from the DEM-PS derived from the TA and vegetation index Landasat-7 obtained images explained only 16% of the variance in SOC area. The small spatial resolution of DEM-PS and images associated with the use only of these predictors were the main factors that influenced the results. Based on these results, the DEM-SRTM and DEM-TOPODATA can be used in DSM semi-detailed soil classes. In the case of the SOC DSM suggest the use of these DEM associated with field control points to verify the precision altimetry and the inclusion of variables related to soil management practices.<br>A demanda por informações quantitativas de solos em nível detalhado de bacias hidrográficas vêm aumentado em decorrência dos cenários globais. O mapeamento digital de solos (MDS) visa gerar dados compatíveis com essas necessidades por meio da geração de mapas funcionais de solos em multi-escalas. O objetivo desse trabalho foi avaliar a qualidade altimétrica e limitações de MDE com a finalidade de auxiliar na escolha do MDE mais adequados para derivar atributos do terreno (AT) para desenvolver funções de predição espacial para serem aplicadas ao mapeamento digital do carbono orgânico do solo em escala de propriedade rural no Planalto do Estado do Rio Grande do Sul (RS). O estudo foi realizado em uma área de 937 ha localizada no município de Giruá, RS, Brasil. Foram coletados 243 pontos amostrais na camada de 0-5 cm e realizado um levantamento planialtimétrico (LP) considerado neste estudo a verdade do terreno dos valores de altitude. Os MDE avaliados foram: MDE-LP (gerado a partir do LP), MDE-CARTA (gerado pela interpolação das curvas de nível da carta topográfica), MDE-ASTER, MDE-SRTM e MDE-TOPODATA. Os MDE foram avaliados quanto à precisão altimétrica por meio de teste estatísticos, valor da raiz quadrada do erro médio quadrático (RMSE) e aplicação da Norma Brasileira de Cartografia para definição da escala de cada MDE com base na precisão da altitude. Os AT derivados de cada MDE foram confrontados com os AT derivados do MDE-LP. Os resultados mostraram que o MDE-LP apresentou a melhor qualidade dos dados de altitude (RMSE = 1,93 m), seguido dos MDE-SRTM (RMSE = 5,95 m), MDE-CARTA (RMSE = 8,28 m), MDE-TOPODATA (RMSE = 9,78 m) e MDE-ASTER (RMSE = 15,57 m). O tamanho da área e relevo suave ondulado foram os principais fatores que influenciaram nos resultados. O MDE-LP se adequou na escala 1:10.000 classe D, enquanto os MDE-CARTA e MDE-SRTM se adequaram na escala 1:50.000 classe B, o MDE-TOPODATA a escala 1:50.000 classe D e o MDE-ASTER escala 1:100.000 classe B. Em relação aos AT, os MDE- SRTM e MDE-TOPODATA apresentam resultados mais próximos do MDE-LP e os menores valores de RMSE para cada AT avaliado. A função de predição construída a partir dos AT derivados do MDE-LP e índice de vegetação obtido de imagens Landasat-7 explicou apenas 16% da variância do COS na área. A resolução espacial pequena do MDE-LP e das imagens associado ao uso apenas dessas variáveis preditoras foram os principais fatores que influenciaram nos resultados. Com base nesses resultados, os MDE- SRTM e MDE-TOPODATA podem ser utilizados no MDS semidetalhado de classes de solos. No caso do MDS do COS sugere-se o uso desses MDE associado com pontos de controle de campo para verificação da precisão altimétrica e a inclusão de variáveis relacionadas a práticas de manejo do solo.
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Jaña, Obregón Ricardo. "Digital elevation models and delineation of antarctic glaciers using stereo capabilities of ASTER satellite images steps on the way for a glacier monitoring on the Antarctic Peninsula /." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:25-opus-37837.
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Ullmann, Tobias [Verfasser], Roland [Gutachter] Baumhauer, Stefan [Gutachter] Dech, and Hans-Wolfgang [Gutachter] Hubberten. "Characterization of Arctic Environment by Means of Polarimetric Synthetic Aperture Radar (PolSAR) Data and Digital Elevation Models (DEM) / Tobias Ullmann. Gutachter: Roland Baumhauer ; Stefan Dech ; Hans-Wolfgang Hubberten." Würzburg : Universität Würzburg, 2015. http://d-nb.info/111178387X/34.
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