Digital Elevation Models: Terminology and Definitions (original) (raw)
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Over the years the study and accurate determination of point elevations and topographic forms of land spaces and sea beds have been the exclusive preserve of Surveyors, Geodesists and Hydrographers and in a derivative sense, Cartographers. Research into diverse environmental phenomena is growing by the day as continuously improving credible results are obtained from computer based Digital Terrain Analysis (DTA), leading to fundamental shifts in engineering solutions and designs and social options in managing the environment. Digital Elevation Models (DEMs) are basic input for the development of Digital Terrain Models (DTMs) which seeks to classify terrain characteristics and behavior for prediction of future environmental phenomena. A continuous digital topographic data structure, the DEM, is foundational to efficient analysis of the landscape as is needed in line of sight determination and in the analysis of topographically influenced environmental phenomena such as, flooding, erosion, stream flow, sediment transportation, runoff distribution etc. The growing efforts today are to express topographic data in continuous digital data structures that either assign an elevation value to every unit of land space, usually in fixed cell sizes, or provide the basic data and algorithm for continuous computation of irregularly sized and sloping triangles across the landscape. These new efforts are purely computational. They are however extending the use of topographic analysis in other vastly expanding areas such as 3-D computer graphics for anatomy and surgery, 3-D movie creations, and 3-D computer printing. A basic fact that makes the involvement of Surveyors imperative in Digital Elevation Model research and development is the proficiency required for adaptation of different geoid models, issues of topo data source scales and accuracy and data geolocation. This paper reviews a few steps of processing different traditional topo data structures to Digital Elevation Models. It makes a few comparisons between the evolving DEM forms and discusses a some applications of the DEM in environmental phenomena analysis. The paper concludes with a call for Surveyor scientists to take their rightful place in the research efforts to move from topographic data structure of discrete spot heights or firm contour lines to dynamic forms of continuous digital topographic data structure, the DEM. A further imperative of this paper is the need to review topographic surveying training curricula to equip upcoming Surveyors with the required skills for DEM development.
Digital elevation models in geomorphology
Hydro-Geomorphology - Models and Trends, 2017
This chapter presents place of geomorphometry in contemporary geomorphology. The focus is on discussing digital elevation models (DEMs) that are the primary data source for the analysis. One has described the genesis and definition, main types, data sources and available free global DEMs. Then we focus on landform parameters, starting with primary morphometric parameters, then morphometric indices and at last examples of morpho-metric tools available in geographic information system (GIS) packages. The last section briefly discusses the landform classification systems which have arisen in recent years.
A comparison of digital elevation models generated from different data sources
Geomorphology, 2009
It can be challenging to accurately determine the topography of physically complex landscapes in remote areas. Ground-based surveys can be difficult, time consuming and may miss significant elements of the landscape. This study compares digital elevation models (DEMs) generated from three different data sources, of the physically complex Narran Lakes Ecosystem, a major floodplain wetland ecosystem in Australia. Topographic surfaces were generated from an airborne laser altimetry (LiDAR) survey, a ground-based differential GPS (DGPS) survey containing more than 20,000 points, and the 9″ DEM of Australia. The LiDARand DGPS-derived data generated a more thorough DEM than the 9″ DEM; however, LiDAR generated a surface topography that yielded significantly more detail than the DGPS survey, with no noticeable loss of elevational accuracy. Both the LiDAR-and the DGPS-derived DEMs compute the overall surface area and volume of the largest floodplain lake within the system to within 1% of each other. LiDAR is shown to be a highly accurate and robust technique for acquiring large quantities of topographic data, even in locations that are unsuitable for ground surveying and where the overall landscape is of exceptionally low relief. The results of this study highlight the potential for LiDAR surveys in the accurate determination of the topography of floodplain wetlands. These data can form an important component of water resource management decisions, particularly where environmental water allocations for these important ecosystems need to be determined.
Review and critical analysis on digital elevation models
Geofizika
Nowadays, digital elevation model (DEM) acts as an inevitable component in the field of remote sensing and GIS. DEM reflects the physical surface of the earth helps to understand the nature of terrain by means of interpreting the landscape using modern techniques and high-resolution satellite images. To understand and analyze the nature of the terrain, DEM is required in many fields in the improvement of developing the product and decision making, mapping purpose, preparing 3D simulations, estimating river channel and creating contour maps to extract the elevation and so on. DEM in various applications will be useful to replicate the overall importance of the availability of worldwide, consistent, high-quality digital elevation models. The present article represents the overall review of DEMs, its generation, development using various techniques derived from topographic maps and high-resolution satellite images over a decade to present. It is useful to understand the nature of topography, address the practical problems and fix them by applying innovative ideas, upcoming high-resolution satellite images and techniques.
Comparison of new and existing global digital elevation models: ASTER G-DEM and SRTM3
Geophysical Research Letters, 2008
1] A new global elevation dataset known as G-DEM, based on the ASTER satellite imagery, will be released in late 2008. G-DEM will be the best freely available global digital elevation model (DEM) at a horizontal resolution of 1 arc second. We assess the quality of G-DEM in comparison with 3-arc-second SRTM DEM, the best current global elevation dataset. Basic geomorphometric parameters (elevation, slope and curvature) were examined for a prerelease version of G-DEM and SRTM DEM for western Japan. G-DEM has fewer missing cells than SRTM DEM, particularly in steep terrain. Also, G-DEM gives smoother and more realistic representations of lowlands, valleys, steep slopes, and mountain ridges, whereas, SRTM DEM includes many local spikes and holes, and tends to overestimate valley-floor elevation and underestimate ridge elevation. G-DEM will be commonly used in geoscientific studies, because of its higher resolution, fewer missing data, and better topographic representation than SRTM DEM.
Advances in Digital Terrain Analysis: The TADTM Initiative
Lecture Notes in Geoinformation and Cartography, 2000
Digital terrain modelling has been one of the most active research and application fields in geo-spatial information science and technology. Using the techniques of computer graphics, the land surface, or terrain surface, can be represented digitally using large volumes of regularly or irregularly distributed sample points, instead of solely relying on the traditional contours or other cartographic symbolism. The term digital terrain model (DTM) is now widely recognized as the digital representation of the terrain surface for a given geographical region.
Geomorpholohy: Digital terrain modeling
This article examines how the methods and data sources used to generate DEMs and calculate land surface parameters have changed over the past 25 years. The primary goal is to describe the state-of-the-art for a typical digital terrain modeling workflow that starts with data capture, continues with data preprocessing and DEM generation, and concludes with the calculation of one or more primary and secondary land surface parameters. The article first describes some of ways in which LiDAR and RADAR remote sensing technologies have transformed the sources and methods for capturing elevation data. It next discusses the need for and various methods that are currently used to preprocess DEMs along with some of the challenges that confront those who tackle these tasks. The bulk of the article describes some of the subtleties involved in calculating the primary land surface parameters that are derived directly from DEMs without additional inputs and the two sets of secondary land surface parameters that are commonly used to model solar radiation and the accompanying interactions between the land surface and the atmosphere on the one hand and water flow and related surface processes on the other. It concludes with a discussion of the various kinds of errors that are embedded in DEMs, how these may be propagated and carried forward in calculating various land surface parameters, and the consequences of this state-of-affairs for the modern terrain analyst.
Digital Surface Models for the Geosciences
Transactions in GIS, 2012
This year the international segment of the symposium focused on one main topic: Surface models for the geosciences. This special issue of Transactions in GIS highlights a selection of nine papers presented at this conference. Recent GIS Ostrava conferences offered a wide scope of topics to share advances of geoinformation technologies and discuss the state-of-the-art of geoinformation. This focus on surface models enabled a better concentration of specialist scientists on the collective theme, and allowed for discussion of the topics in greater detail. The alignment of the conference was based on the experience that surface models are frequently used for many applications in the geosciences. Models with different scales, various data sources, alternative construction approaches and representations are sought to best fit the given purpose. The common focus is a model of a quality adequate to satisfy our needs and efficiency requirements. The control of quality is essential for managing uncertainty in our processing and decision making. Extensive field studies and research have been conducted to address these issues. The aim of the conference was to present and discuss new methods, issues and challenges encountered in all parts of a complex process of gradual development and utilization of digital surface models. The process covers data capture, storage, model creation, validation, manipulation, visualization and utilization. Each phase requires adequate methods and contains issues which may substantially decrease the value of the model. Surface models play important roles in a wide spectrum of domains. The conference also provided a platform for discussing requirements, features and research approaches to virtual reality, 3D object modelling, continuous field modelling and other geoscience applications. This vision led to defining a conference programme classified into these thematic areas: • LiDAR for elevation data • Radar interferometry and GPS for elevation data • Surface model creation • Surface model storage bs_bs_banner