150 resultados para DTM
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This paper compares the applicability of three ground survey methods for modelling terrain: one man electronic tachymetry (TPS), real time kinematic GPS (GPS), and terrestrial laser scanning (TLS). Vertical accuracy of digital terrain models (DTMs) derived from GPS, TLS and airborne laser scanning (ALS) data is assessed. Point elevations acquired by the four methods represent two sections of a mountainous area in Cumbria, England. They were chosen so that the presence of non-terrain features is constrained to the smallest amount. The vertical accuracy of the DTMs was addressed by subtracting each DTM from TPS point elevations. The error was assessed using exploratory measures including statistics, histograms, and normal probability plots. The results showed that the internal measurement accuracy of TPS, GPS, and TLS was below a centimetre. TPS and GPS can be considered equally applicable alternatives for sampling the terrain in areas accessible on foot. The highest DTM vertical accuracy was achieved with GPS data, both on sloped terrain (RMSE 0.16. m) and flat terrain (RMSE 0.02. m). TLS surveying was the most efficient overall but veracity of terrain representation was subject to dense vegetation cover. Therefore, the DTM accuracy was the lowest for the sloped area with dense bracken (RMSE 0.52. m) although it was the second highest on the flat unobscured terrain (RMSE 0.07. m). ALS data represented the sloped terrain more realistically (RMSE 0.23. m) than the TLS. However, due to a systematic bias identified on the flat terrain the DTM accuracy was the lowest (RMSE 0.29. m) which was above the level stated by the data provider. Error distribution models were more closely approximated by normal distribution defined using median and normalized median absolute deviation which supports the use of the robust measures in DEM error modelling and its propagation. © 2012 Elsevier Ltd.
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1. The prediction and mapping of climate in areas between climate stations is of increasing importance in ecology.
2. Four categories of model, simple interpolation, thin plate splines, multiple linear regression and mixed spline-regression, were tested for their ability to predict the spatial distribution of temperature on the British mainland. The models were tested by external cross-verification.
3. The British distribution of mean daily temperature was predicted with the greatest accuracy by using a mixed model: a thin plate spline fitted to the surface of the country, after correction of the data by a selection from 16 independent topographical variables (such as altitude, distance from the sea, slope and topographic roughness), chosen by multiple regression from a digital terrain model (DTM) of the country.
4. The next most accurate method was a pure multiple regression model using the DTM. Both regression and thin plate spline models based on a few variables (latitude, longitude and altitude) only were comparatively unsatisfactory, but some rather simple methods of surface interpolation (such as bilinear interpolation after correction to sea level) gave moderately satisfactory results. Differences between the methods seemed to be dependent largely on their ability to model the effect of the sea on land temperatures.
5. Prediction of temperature by the best methods was greater than 95% accurate in all months of the year, as shown by the correlation between the predicted and actual values. The predicted temperatures were calculated at real altitudes, not subject to sea-level correction.
6. A minimum of just over 30 temperature recording stations would generate a satisfactory surface, provided the stations were well spaced.
7. Maps of mean daily temperature, using the best overall methods are provided; further important variables, such as continentality and length of growing season, were also mapped. Many of these are believed to be the first detailed representations at real altitude.
8. The interpolated monthly temperature surfaces are available on disk.
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Introdução: A disfunção temporomandibular (DTM), de causa muscular, caracteriza-se por uma dor músculo-esquelética crónica, com sinais e sintomas específicos como a presença de Trigger Points (TrPs). Objetivo: Avaliar o efeito da Técnica de Inibição de Jones (TIJ) nos músculos masseter e temporal em indivíduos com DTM, e a identificação dos sinais e sintomas, a relação entre a severidade da DTM, a ansiedade e a qualidade de sono. Métodos: Estudo quasi-experimental, constituído por 16 indivíduos no grupo experimental (GE) e 17 grupo controle (GC). O grau de severidade foi avaliado pelo Índice de Helkimo e as alterações do sono pelo questionário de Pittsburgh sobre a qualidade do sono. Apenas o GE foi sujeito a uma TIJ nos TrPs latentes dos músculos masseter e temporal. Os dois grupos foram avaliados pré-intervenção (M0), pós-intervenção (M1) e 3 semanas após (M2), as amplitudes de movimento ativas de abertura, lateralidade direita/esquerda e protusão da boca bem como a dor (EVA) em repouso e na abertura máxima. Resultados: Foi possível observar que quanto maior o grau de DTM, maior a frequência de ansiedade e pior a qualidade do sono. Observou-se um decréscimo de TrPs, no GE, após a aplicação da técnica, principalmente no masseter. Não foi possível verificar diferenças inter-grupos. Contudo, observou-se no GE uma melhoria em todas as amplitudes avaliadas entre o M0 e o M2. Em relação à EVA em repouso e na abertura máxima, o GE demonstrou diminuição da dor no M1 e manteve valores inferiores no M2. Conclusão: Verifica-se uma diminuição dos TrPs, uma melhoria das amplitudes ativas bem como uma diminuição da dor após a aplicação da TIJ no GE. Já ao longo do tempo, o efeito é menos expressivo contudo observam-se valores inferiores comparativamente a M0.
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INTRODUCTION : L’articulation temporo-mandibulaire (ATM) est un système articulaire excessivement complexe. L'étiologie des désordres temporo-mandibulaires (DTM) est encore incertaine et le lien de cause à effet des traitements orthodontiques en tant que facteur de risque est une question qui a longuement été discutée. Cette étude clinique prospective vise à évaluer les effets à long terme du port continu de coquilles correctrices Invisalign® sur l’ATM et les muscles du complexe facial. MATÉRIELS ET MÉTHODES : L'étude incluait 43 adolescents et adultes âgés entre 13 et 51 ans (25 femmes et 18 hommes). Deux d'entre eux ont été exclus en raison de mauvaise coopération causant l’arrêt du traitement orthodontique. Les effets dans le temps des coquilles sur l'ATM et les muscles du complexe facial ont été évalués en utilisant l’examen du Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). Le nombre de contractions musculaires durant le sommeil a été mesuré objectivement par enregistrements électromyographiques (EMG) et la fréquence de grincement et de serrement des dents à l’éveil a été rapportée subjectivement par les patients à l’aide de questionnaires. Des mesures répétées ont été effectuées aux temps suivants: avant le début du traitement pour les données contrôles (T1), deux semaines (T2), et six mois (T3) après le début du traitement. Les données numériques ont été analysées par l’analyse de variance (ANOVA) en mesures répétées et la méthode de Brunner-Langer, alors que les données nominales ont été évaluées par le test de Cochran-Mantel-Haenszel. Les résultats ont été considérés significatifs si p < 0.05. RÉSULTATS ET DISCUSSION : Le nombre de contractions musculaires par heure (index) durant le sommeil et leur durée moyenne n’ont pas été statistiquement différents entre les trois nuits d’enregistrement EMG (Brunner Langer, p > 0.005). Cependant, 67 % des participants ont rapporté avoir eu du grincement ou du serrement des dents la nuit au T2 et 64 % au T3 comparativement à 39 % au T1, ce qui était une augmentation significative (Cochran-Mantel-Haenszel, p = 0.0112). Quarante-quatre pour cent des patients ont signalé du grincement ou du serrement des dents pendant le jour au T1, tandis qu'un pourcentage nettement plus élevé de 66 % en a rapporté au T2 et 61 % au T3 (Cochran-Mantel-Haenszel, p = 0.0294). Au T1, 12 % des sujets ont indiqué qu'ils se sont réveillés avec une douleur musculaire, comparativement à 29 % au T2, ce qui était une augmentation significative (Cochran-Mantel-Haenszel, p = 0.0347). Au T2, il y avait une réduction significative des mouvements maximaux de la mandibule dans toutes les directions (ANOVA en mesures répétées, p < 0,05). De plus, il y a eu une augmentation significative du nombre de sites douloureux et de l'intensité de la douleur à la palpation de l'ATM et des muscles faciaux avec l'évaluation du RDC/TMD au T2 en comparaison aux T1 et T3 (Brunner Langer, p < 0,05). CONCLUSION : La présente étude n’a révélé aucun effet des coquilles sur l’activité oro-faciale durant le sommeil au fil du temps mesurée objectivement à l’aide des enregistrements EMG, mais une augmentation significative de la fréquence du grincement et du serrement des dents rapportée subjectivement par les patients au moyen des questionnaires aux T2 et T3. Au T2, il y avait une augmentation significative des symptômes de l'ATM et des muscles du complexe oro-facial, mais ces symptômes sont retournés au niveau initial avec le temps.
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La tecnología LiDAR (Light Detection and Ranging), basada en el escaneado del territorio por un telémetro láser aerotransportado, permite la construcción de Modelos Digitales de Superficie (DSM) mediante una simple interpolación, así como de Modelos Digitales del Terreno (DTM) mediante la identificación y eliminación de los objetos existentes en el terreno (edificios, puentes o árboles). El Laboratorio de Geomática del Politécnico de Milán – Campus de Como- desarrolló un algoritmo de filtrado de datos LiDAR basado en la interpolación con splines bilineares y bicúbicas con una regularización de Tychonov en una aproximación de mínimos cuadrados. Sin embargo, en muchos casos son todavía necesarios modelos más refinados y complejos en los cuales se hace obligatorio la diferenciación entre edificios y vegetación. Este puede ser el caso de algunos modelos de prevención de riesgos hidrológicos, donde la vegetación no es necesaria; o la modelización tridimensional de centros urbanos, donde la vegetación es factor problemático. (...)
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La Vía Augusta era una vía romana que iba desde Cádiz hasta Roma. Estaba compuesta de un ramal principal y de diversos ramales secundarios que en su mayoría, constituyen el sustrato de la actual red principal de carreteras del Mediterráneo en la Península Ibérica. A pesar de ello, no se conoce la localización exacta de muchos de esos ramales. El presente artículo muestra un estudio de por dónde deberían atravesar, posiblemente, las rutas romanas el Pirineo Oriental. Para el cálculo de estas rutas se aplica un algoritmo de mínimo coste que incorpora diversas variables y que tiene en cuenta que el desplazamiento se lleva a cabo a pie, y siguiendo la orografía del terreno. Se utilizan en el proceso las herramientas de análisis de costes y el cálculo de rutas óptimas que incorpora SEXTANTE. En particular se estudia y se modela la ruta de mínimo coste anisotrópica, es decir aquella en la que es importante la dirección del movimiento. El proceso consiste en analizar diversas rutas de mínimo coste, entendiendo como coste el esfuerzo en recorrerla. Se busca, por tanto, el camino que sea más sencillo de recorrer teniendo en cuenta principalmente la orografía del terreno (MDT), la pendiente y su orientación. Además, en el estudio se tienen en cuenta otras variables como los usos de suelo, la red hidrográfica, la red de comunicaciones romana conocida, así como la ubicación de puentes y asentamientos romanos entre otros. Las diferentes rutas obtenidas se contrastan con las rutas propuestas por los historiadores y arqueólogos
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La visualización 3D ofrece una serie de ventajas y funcionalidades cada vez más demandadas, por lo que es conveniente su incorporación a las aplicaciones GIS. El sistema propuesto integra la vista 2D propia de un GIS y la vista 3D garantizando la interacción entre ellas y teniendo por resultado una solución GIS integral. Se permite la carga de Modelos Digitales del Terreno (MDT), de forma directa o empleando servicios OGC-CSW, para la proyección de los elementos 2D, así como la carga de modelos 3D. Además el sistema está dotado de herramientas para extrusión y generación automática de volúmenes empleando parámetros existentes en la información 2D. La generación de las construcciones a partir de su altura y la elaboración de redes tridimensionales a partir de la profundidad en las infraestructuras son algunos casos prácticos de interés. Igualmente se permite no sólo la consulta y visualización sino también la edición 3D, lo que supone una importante ventaja frente a otros sistemas 3D. LocalGIS, Sistema de Información Territorial de software libre aplicado a la gestión municipal, es el sistema GIS empleado para la incorporación del prototipo. Se permite por lo tanto aplicar todas las ventajas y funcionalidades propias del 3D a la gestión municipal que LocalGIS realiza. Esta tecnología ofrece un campo de aplicaciones muy amplio y prometedor
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Flood modelling of urban areas is still at an early stage, partly because until recently topographic data of sufficiently high resolution and accuracy have been lacking in urban areas. However, Digital Surface Models (DSMs) generated from airborne scanning laser altimetry (LiDAR) having sub-metre spatial resolution have now become available, and these are able to represent the complexities of urban topography. The paper describes the development of a LiDAR post-processor for urban flood modelling based on the fusion of LiDAR and digital map data. The map data are used in conjunction with LiDAR data to identify different object types in urban areas, though pattern recognition techniques are also employed. Post-processing produces a Digital Terrain Model (DTM) for use as model bathymetry, and also a friction parameter map for use in estimating spatially-distributed friction coefficients. In vegetated areas, friction is estimated from LiDAR-derived vegetation height, and (unlike most vegetation removal software) the method copes with short vegetation less than ~1m high, which may occupy a substantial fraction of even an urban floodplain. The DTM and friction parameter map may also be used to help to generate an unstructured mesh of a vegetated urban floodplain for use by a 2D finite element model. The mesh is decomposed to reflect floodplain features having different frictional properties to their surroundings, including urban features such as buildings and roads as well as taller vegetation features such as trees and hedges. This allows a more accurate estimation of local friction. The method produces a substantial node density due to the small dimensions of many urban features.
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Flooding is a major hazard in both rural and urban areas worldwide, but it is in urban areas that the impacts are most severe. An investigation of the ability of high resolution TerraSAR-X data to detect flooded regions in urban areas is described. An important application for this would be the calibration and validation of the flood extent predicted by an urban flood inundation model. To date, research on such models has been hampered by lack of suitable distributed validation data. The study uses a 3m resolution TerraSAR-X image of a 1-in-150 year flood near Tewkesbury, UK, in 2007, for which contemporaneous aerial photography exists for validation. The DLR SETES SAR simulator was used in conjunction with airborne LiDAR data to estimate regions of the TerraSAR-X image in which water would not be visible due to radar shadow or layover caused by buildings and taller vegetation, and these regions were masked out in the flood detection process. A semi-automatic algorithm for the detection of floodwater was developed, based on a hybrid approach. Flooding in rural areas adjacent to the urban areas was detected using an active contour model (snake) region-growing algorithm seeded using the un-flooded river channel network, which was applied to the TerraSAR-X image fused with the LiDAR DTM to ensure the smooth variation of heights along the reach. A simpler region-growing approach was used in the urban areas, which was initialized using knowledge of the flood waterline in the rural areas. Seed pixels having low backscatter were identified in the urban areas using supervised classification based on training areas for water taken from the rural flood, and non-water taken from the higher urban areas. Seed pixels were required to have heights less than a spatially-varying height threshold determined from nearby rural waterline heights. Seed pixels were clustered into urban flood regions based on their close proximity, rather than requiring that all pixels in the region should have low backscatter. This approach was taken because it appeared that urban water backscatter values were corrupted in some pixels, perhaps due to contributions from side-lobes of strong reflectors nearby. The TerraSAR-X urban flood extent was validated using the flood extent visible in the aerial photos. It turned out that 76% of the urban water pixels visible to TerraSAR-X were correctly detected, with an associated false positive rate of 25%. If all urban water pixels were considered, including those in shadow and layover regions, these figures fell to 58% and 19% respectively. These findings indicate that TerraSAR-X is capable of providing useful data for the calibration and validation of urban flood inundation models.
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Chess endgame tables should provide efficiently the value and depth of any required position during play. The indexing of an endgame’s positions is crucial to meeting this objective. This paper updates Heinz’ previous review of approaches to indexing and describes the latest approach by the first and third authors. Heinz’ and Nalimov’s endgame tables (EGTs) encompass the en passant rule and have the most compact index schemes to date. Nalimov’s EGTs, to the Distance-to-Mate (DTM) metric, require only 30.6 × 10^9 elements in total for all the 3-to-5-man endgames and are individually more compact than previous tables. His new index scheme has proved itself while generating the tables and in the 1999 World Computer Chess Championship where many of the top programs used the new suite of EGTs.
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Chess endgame tables should provide efficiently the value and depth of any required position during play. The indexing of an endgame’s positions is crucial to meeting this objective. This paper updates Heinz’ previous review of approaches to indexing and describes the latest approach by the first and third authors. Heinz’ and Nalimov’s endgame tables (EGTs) encompass the en passant rule and have the most compact index schemes to date. Nalimov’s EGTs, to the Distance-to-Mate (DTM) metric, require only 30.6 × 109 elements in total for all the 3-to-5-man endgames and are individually more compact than previous tables. His new index scheme has proved itself while generating the tables and in the 1999 World Computer Chess Championship where many of the top programs used the new suite of EGTs.
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This article reports the combined results of several initiatives in creating and surveying complete suites of endgame tables (EGTs) to the Depth to Mate (DTM) and Depth to Conversion (DTC) metrics. Data on percentage results, maximals and mutual zugzwangs, mzugs, has been filed and made available on the web, as have the DTM EGTs.
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The Endgame Tables Online initiative and p2p community have made available all published Nalimov DTM EGTs. It now looks forward to the 16 unpublished EGTs computed by August 9th and presumed to be still in existence, particularly as Marc Bourzutschky’s FEG results independently confirm all Nalimov’s published 3-3p DTM EGT statistics including those for KPPKPP.
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A report of the new Bourzutschky/Konoval chess endgame depth record of DTC = 330 moves, and of the progress of the Kryukov peer-group to disseminate Nalimov's DTM EGTs. The question of data integrity and assurance is raised.
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Airborne scanning laser altimetry (LiDAR) is an important new data source for river flood modelling. LiDAR can give dense and accurate DTMs of floodplains for use as model bathymetry. Spatial resolutions of 0.5m or less are possible, with a height accuracy of 0.15m. LiDAR gives a Digital Surface Model (DSM), so vegetation removal software (e.g. TERRASCAN) must be used to obtain a DTM. An example used to illustrate the current state of the art will be the LiDAR data provided by the EA, which has been processed by their in-house software to convert the raw data to a ground DTM and separate vegetation height map. Their method distinguishes trees from buildings on the basis of object size. EA data products include the DTM with or without buildings removed, a vegetation height map, a DTM with bridges removed, etc. Most vegetation removal software ignores short vegetation less than say 1m high. We have attempted to extend vegetation height measurement to short vegetation using local height texture. Typically most of a floodplain may be covered in such vegetation. The idea is to assign friction coefficients depending on local vegetation height, so that friction is spatially varying. This obviates the need to calibrate a global floodplain friction coefficient. It’s not clear at present if the method is useful, but it’s worth testing further. The LiDAR DTM is usually determined by looking for local minima in the raw data, then interpolating between these to form a space-filling height surface. This is a low pass filtering operation, in which objects of high spatial frequency such as buildings, river embankments and walls may be incorrectly classed as vegetation. The problem is particularly acute in urban areas. A solution may be to apply pattern recognition techniques to LiDAR height data fused with other data types such as LiDAR intensity or multispectral CASI data. We are attempting to use digital map data (Mastermap structured topography data) to help to distinguish buildings from trees, and roads from areas of short vegetation. The problems involved in doing this will be discussed. A related problem of how best to merge historic river cross-section data with a LiDAR DTM will also be considered. LiDAR data may also be used to help generate a finite element mesh. In rural area we have decomposed a floodplain mesh according to taller vegetation features such as hedges and trees, so that e.g. hedge elements can be assigned higher friction coefficients than those in adjacent fields. We are attempting to extend this approach to urban area, so that the mesh is decomposed in the vicinity of buildings, roads, etc as well as trees and hedges. A dominant points algorithm is used to identify points of high curvature on a building or road, which act as initial nodes in the meshing process. A difficulty is that the resulting mesh may contain a very large number of nodes. However, the mesh generated may be useful to allow a high resolution FE model to act as a benchmark for a more practical lower resolution model. A further problem discussed will be how best to exploit data redundancy due to the high resolution of the LiDAR compared to that of a typical flood model. Problems occur if features have dimensions smaller than the model cell size e.g. for a 5m-wide embankment within a raster grid model with 15m cell size, the maximum height of the embankment locally could be assigned to each cell covering the embankment. But how could a 5m-wide ditch be represented? Again, this redundancy has been exploited to improve wetting/drying algorithms using the sub-grid-scale LiDAR heights within finite elements at the waterline.