Changing the Light Azimuth in Shaded Relief Representation by Clustering Aspect
TL;DR: A GIS tool to enhance the visual quality of hillshading by developing a technique based on clustering aspect to provide a seamless change of lighting throughout the scene and embedded into an ArcGIS toolbox.
Abstract: Manual shading, traditionally produced manually by specifically trained cartographers, is still considered superior to automatic methods, particularly for mountainous landscapes. However, manual shading is time-consuming and its results depend on the cartographer and as such difficult to replicate consistently. For this reason there is a need to create an automatic method to standardize its results. A crucial aspect of manual shading is the continuous change of light direction (azimuth) and angle (zenith) in order to better highlight discrete landforms. Automatic hillshading algorithms, widely available in many geographic information systems (GIS) applications, do not provide this feature. This may cause the resulting shaded relief to appear flat in some areas, particularly in areas where the light source is parallel to the mountain ridge. In this work we present a GIS tool to enhance the visual quality of hillshading. We developed a technique based on clustering aspect to provide a seamless chang...
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01 Jan 1979
TL;DR: In this article, a system is described which replaces existing sets of diverse terrain indices with a group of statistics for point-characteristics, and calculates all of these statistics in a single computer run from a single data set.
Abstract: : A system is described which: (a) replaces existing sets of diverse terrain indices with a group of statistics for point-characteristics; (b) calculates all of these statistics in a single computer run from a single data set; and (c) utilizes available altitude matrix data The procedures are applicable to Altitude matrix data at any grid mesh From altitudes in each 3 x 3 submatrix, a quadratic surface is fitted and solved for its first and second horizontal and vertical derivatives at the central point This yields the slope gradient, slope aspect, profile convexity, and plan convexity at every point in the original matrix, except for the peripheral rows and columns These 'point' descriptors are presented as: (1) line-printer shaded maps; (2) histograms; (3) scatter plots of each pair; (4) matrix of pair-wise correlations, plus circular regressions on aspect, and several multiple regressions, and (5) summary (moment-based) statistics In general, the five basic descriptors have little relation to each other, except that gradient is usually a quadratic function of altitude A comparison is made with other approaches, such as spectral analysis and fractal modelling The long-distance persistence properties of terrain mean that considerable extra variance at long wavelengths is usually incorporated when the study area is extended Hence the auto correlation function varies with the length of series or size of area Variance of derivatives are also affected, but means, skews, and kurtoses are not
352 citations
TL;DR: The quality of the shaded relief is superior to the standard method, but the level of automation and standardisation guarantees consistent and reproducible results.
24 citations
TL;DR: Several techniques which combine hillshade with other relief data layers derived from DEM are presented and an assessment of advantages and disadvantages of their visualization are presented.
Abstract: Abstract The aim of the article is to present different relief visualization techniques created using only free and open source GIS tools, such as QGIS and RVT. The criteria for selection of these techniques are that they should be, on the one hand, simple and fast for implementation and on the other suitable for multiple visualization purposes. Here we present several techniques which combine hillshade with other relief data layers derived from DEM and an assessment of advantages and disadvantages of their visualization.
16 citations
TL;DR: The goal is to increase the reproducibility of terrain rendering algorithms and techniques across different scales and landscapes by introducing elevation models of varying terrain types, available to the user at no cost, with minimal common data imperfections.
Abstract: This paper proposes elevation models to promote, evaluate, and compare various terrain representation techniques. Our goal is to increase the reproducibility of terrain rendering algorithms and tec...
16 citations
TL;DR: The results showed that presence/absence models were successful in the implementation and well distinguished the points of presence and pseudo-absence from each other, and the conservation revealed that the heights along with the caves inside them could be a protective priority to counteract the effects of climate change.
Abstract: Climate change, as an emerging phenomenon, has led to changes in the distribution, movement, and even risk of extinction of various wildlife species and this has raised concerns among conservation biologists. Different species have two options in the face of climate change, either to adopt or follow their climatic niche to new places through the connectivity of habitats. The modeling of interpatch landscape communications can serve as an effective decision support tool for wildlife managers. This study was conducted to assess the effects of climate change on the distribution and habitat connectivity of the endangered subspecies of Asian black bear (Ursus thibetanus gedrosianus) in the southern and southeastern Iran. The presence points of the species were collected in Provinces of Kerman, Hormozgan, and Sistan-Baluchestan. Habitat modeling was done by the Generalized Linear Model, and 3 machine learning models including Maximum Entropy, Back Propagation based artificial Neural Network, and Support Vector Machine. In order to achieve the ensemble model, the results of the mentioned models were merged based on the method of "accuracy rate as weight" derived from their validation. To construct pseudo-absence points for the use in the mentioned models, the Ensemble model of presence-only models was used. The modeling was performed using 15 habitat variables related to climatic, vegetation, topographic, and anthropogenic parameters. The three general circulation models of BCC-CSM1, CCSM4, and MRI-CGCM3 were selected under the two scenarios of RCP2.6 and RCP8.5 by 2070. To investigate the effect of climate change on the habitat connections, the protected areas of 3 provinces were considered as focal nodes and the connections between them were established based on electrical circuit theory and Pairwise method. The true skill statistic was employed to convert the continuous suitability layers to binary suitable/unsuitable range maps to assess the effectiveness of the protected areas in the coverage of suitable habitats for the species. Due to the high power of the stochastic forest model in determining the importance of variables, this method was used. The results showed that presence/absence models were successful in the implementation and well distinguished the points of presence and pseudo-absence from each other. Based on the random forests model, the variables of Precipitation of Driest Quarter, Precipitation of Coldest Quarter, and Temperature Annual Range have the greatest impact on the habitat suitability. Comparing the modeling findings to the realities of the species distribution range indicated that the suitable habitats are located in areas with high humidity and rainfall, which are mostly in the northern areas of Bandar Abbas, south of Kerman, and west and south of Sistan-Baluchestan. The area of suitable habitats, in the MRI-CGCM3 (189731 Km2) and CCSM4 (179007 Km2) models under the RCP2.6 scenario, is larger than the current distribution (174001 Km2). However, in terms of the performance of protected areas, the optimal coverage of the species by the boundary of the protected areas, under each of the RCP2.6 and RCP8.5 scenarios, is less than the present time. According to the electric circuit theory, connecting the populations in the protected areas of Sistan-Baluchestan province to those in the northern Hormozgan and the southern Kerman would be based on the crossing through the heights of Sistan-Baluchestan and Hormozgan provinces and the plains between these heights would be the movement pinch points under the current and future scenarios. Populations in the protected areas of Kerman have higher quality patch connections than that of the other two provinces. The areas such as Sang-e_Mes, Kouh_Shir, Zaryab, and Bahr_Aseman in Kerman Province and Kouhbaz and Geno in Hormozgan Province can provide suitable habitats for the species in the distribution models. The findings revealed that the conservation of the heights along with the caves inside them could be a protective priority to counteract the effects of climate change on the species.
15 citations
References
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Book•
01 Jan 1990TL;DR: An electrical signal transmission system, applicable to the transmission of signals from trackside hot box detector equipment for railroad locomotives and rolling stock, wherein a basic pulse train is transmitted whereof the pulses are of a selected first amplitude and represent a train axle count.
Abstract: 1. Introduction. 2. Partitioning Around Medoids (Program PAM). 3. Clustering large Applications (Program CLARA). 4. Fuzzy Analysis. 5. Agglomerative Nesting (Program AGNES). 6. Divisive Analysis (Program DIANA). 7. Monothetic Analysis (Program MONA). Appendix 1. Implementation and Structure of the Programs. Appendix 2. Running the Programs. Appendix 3. Adapting the Programs to Your Needs. Appendix 4. The Program CLUSPLOT. References. Author Index. Subject Index.
10,537 citations
"Changing the Light Azimuth in Shade..." refers methods in this paper
...In this research, we used the common k-means algorithm (Kaufman and Rousseeuw, 1990) that divides the dataset based on the distance between each element of the dataset and a set of centroids....
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01 Jan 1990
TL;DR: In this article, an electrical signal transmission system for railway locomotives and rolling stock is proposed, where a basic pulse train is transmitted whereof the pulses are of a selected first amplitude and represent a train axle count, and a spike pulse of greater selected amplitude is transmitted, occurring immediately after the axle count pulse to which it relates, whenever an overheated axle box is detected.
Abstract: An electrical signal transmission system, applicable to the transmission of signals from trackside hot box detector equipment for railroad locomotives and rolling stock, wherein a basic pulse train is transmitted whereof the pulses are of a selected first amplitude and represent a train axle count, and a spike pulse of greater selected amplitude is transmitted, occurring immediately after the axle count pulse to which it relates, whenever an overheated axle box is detected. To enable the signal receiving equipment to determine on which side of a train the overheated box is located, the spike pulses are of two different amplitudes corresponding, respectively, to opposite sides of the train.
9,011 citations
TL;DR: This book make understandable the cluster analysis is based notion of starsmodern treatment, which efficiently finds accurate clusters in data and discusses various types of study the user set explicitly but also proposes another.
Abstract: The Wiley-Interscience Paperback Series consists of selected books that have been made more accessible to consumers in an effort to increase In both the increasingly important and distribution we show how these methods. Our experiments demonstrate that together can deal with most applications technometrics. In an appropriate visualization technique is to these new. The well written and efficiently finds accurate clusters in data including. Of applied value for several preprocessing tasks discontinuity preserving smoothing feature clusters! However the model based notion of domain knowledge from real data repositories in data. Discusses various types of study the user set explicitly but also propose another. This book make understandable the cluster analysis is based notion of starsmodern treatment.
7,423 citations
"Changing the Light Azimuth in Shade..." refers methods in this paper
...In this research, we used the common k-means algorithm (Kaufman and Rousseeuw, 1990) that divides the dataset based on the distance 292 The Cartographic Journal...
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...In this research, we used the common k-means algorithm (Kaufman and Rousseeuw, 1990) that divides the dataset based on the distance between each element of the dataset and a set of centroids....
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01 Jan 2001
TL;DR: In this article, a fine-scale classification of ridge lines and valleys is presented, including lateral drainages in the major valleys, and the bottoms of the major canyons are classified as flat areas.
Abstract: Using tpi300 (Fig. 3b), many individual ridge lines and valleys are delineated at a fine scale, including lateral drainages in the major valleys, and the bottoms of the major canyons are classified as flat areas. At tpi2000, the classification shows the major landforms (Fig. 3c): mountains, major ridge lines, and the major valleys and canyons. Smaller lateral features disappear, and canyons bottoms are now classified as valleys.
615 citations
"Changing the Light Azimuth in Shade..." refers background or methods in this paper
...Several methods are available in literature to extract linear features and other landforms from DEMs (few examples are: Dikau, 1989; Wood, 1996; Pike, 1988; Burrough et al., 2000; Weiss, 2001; van Asselen and Seijmonsbergen, 2006; Iwahashi and Pike, 2007; Jasiewicz and Stepinski, 2013), each with its pros and cons, and a perfect method does not seem to exist....
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...…literature to extract linear features and other landforms from DEMs (few examples are: Dikau, 1989; Wood, 1996; Pike, 1988; Burrough et al., 2000; Weiss, 2001; van Asselen and Seijmonsbergen, 2006; Iwahashi and Pike, 2007; Jasiewicz and Stepinski, 2013), each with its pros and cons, and a…...
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...Several methods are available in literature to extract linear features and other landforms from DEMs (few examples are: Dikau, 1989; Wood, 1996; Pike, 1988; Burrough et al., 2000; Weiss, 2001; van Asselen and Seijmonsbergen, 2006; Iwahashi and Pike, 2007; Jasiewicz and Stepinski, 2013), each with its pros and cons, and a perfect method does not seem to exist....
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...This translates into a bright white tone for valleys that hide the noise typical of high resolution DEMs, and a progressively darker tone at high altitudes, which enhance the sharpness of the ridges....
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Dissertation•
01 Jan 1996
TL;DR: 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, and the most effective error characterisations are found to be those that identify high frequency spatial pattern.
Abstract: 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.
566 citations
"Changing the Light Azimuth in Shade..." refers methods in this paper
...Several methods are available in literature to extract linear features and other landforms from DEMs (few examples are: Dikau, 1989; Wood, 1996; Pike, 1988; Burrough et al., 2000; Weiss, 2001; van Asselen and Seijmonsbergen, 2006; Iwahashi and Pike, 2007; Jasiewicz and Stepinski, 2013), each with its pros and cons, and a perfect method does not seem to exist....
[...]
...Several methods are available in literature to extract linear features and other landforms from DEMs (few examples are: Dikau, 1989; Wood, 1996; Pike, 1988; Burrough et al., 2000; Weiss, 2001; van Asselen and Seijmonsbergen, 2006; Iwahashi and Pike, 2007; Jasiewicz and Stepinski, 2013), each with…...
[...]
...Several methods are available in literature to extract linear features and other landforms from DEMs (few examples are: Dikau, 1989; Wood, 1996; Pike, 1988; Burrough et al., 2000; Weiss, 2001; van Asselen and Seijmonsbergen, 2006; Iwahashi and Pike, 2007; Jasiewicz and Stepinski, 2013), each with its pros and cons, and a perfect method does not seem to exist....
[...]
...This translates into a bright white tone for valleys that hide the noise typical of high resolution DEMs, and a progressively darker tone at high altitudes, which enhance the sharpness of the ridges....
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