Terrain Digital Elevation Model Research Articles

Producing Erosion Risk Map Using Remote Sensing Techniques and RUSLE Method in Halfalı Stream Watershed of Kahramanmaras

In this study, it is aimed to determine the potential erosion risk condition of the area using remote sensing techniques and RUSLE method in Halfalı Stream Watershed, which is 25 km away from Kahramanmaras province. With the purpose of applying this method, rainfall erosivitiy index (R) has been generated by means of modified fournier index (MFI).Soil erodibility factor (K) has been produced using Inverse Distance Weighted technique and soil sample obtained from study area. Slope length and slope steepness factor (LS) has been created by the help of digital terrain elevation model. Vegetation management factor (C) has been generated using remote sensing techniques. Whole factors obtained have been overlapped in Geographic Information System (GIS) and soil loss belonging to study area has been determined using raster calculator command within map algebra module. It has been divided into 5 classes and erosion risk map has been produced. According to potential erosion risk map obtained, 60.35 % of area has been subject to very low erosion risk, while 2.60% , 6.08 %, 10.37 % and 20.60 % has been subject to low, medium, high and very high erosion risk, respectively.

Noteworthy record of the kit fox (Vulpes macrotis) and its relation to physiographic characteristics in Baja California, Mexico

The kit fox (Vulpes macrotis) lives in sandy and shallow soils of the Pacific coastal plains and the ecoregion of San Felipe desert. The reports of this species are scarce and in Mexico it is listed as a threatened species. The populations of V. macrotis tend to decrease due to the change in the habitat to agricultural land, which has been one of the causes of the disappearance of kit fox populations in Mexico. As part of the project “Characterisation of water bodies in Sierra Santa Isabel, Baja California”, 12 camera traps were placed in six watering holes that are visited by wildlife from January to August 2015. Digital terrain elevation models were used to describe three variables: roughness, slope inclination and orientation; these variables are essential for the kit fox to build its burrows, catch its preys and escape from predators. The analyses were also carried out in localities where this carnivore had previously been recorded in Baja California. An analysis of variance was used to determine the existence of similarities or differences between the topographical characteristics of the historical localities and the new record. The first photographic record of the kit fox was obtained in one of the watering holes located within the Valle de los Cirios Flora and Fauna Protection Area. The analyses of variance confirmed that there are no significant differences between roughness (F 4, 780 = 0.11, P > 0.05), slope inclination (F 4, 1275 = 0.319, P > 0.05) and orientation (F 4, 15 = 0.41, P > 0.05), between the historical localities and the site where the new record was obtained. Other carnivores were also recorded in the watering hole, such as the cougar (Puma concolor), bobcat (Lynx rufus), coyote (Canis latrans) and gray fox (Urocyon cinereoargenteus). The presence of the kit fox is likely occasional in the watering hole, because the slopes are greater than 10 degrees and, therefore, these sites are unsuitable for the construction of burrows. However, flat sites with sandy substrates that empty into the Gulf of California occur at a distance of less than 5 km from the watering hole, which are therefore suitable to be inhabited by the kit fox. The analysis of topographic variables of the historical records coupled with camera traps jointly confirmed that the site with the new record has characteristics that are suitable for the kit fox.

Analysis of the relationships between the spatial arrangement of palaeovalleys and contemporary valleys of Central Poland in the light of GIS methods

The article presents an example of application of selected GIS methods for showing connections between the course of palaeovalleys and contemporary valleys in Central Poland. The analysed area was shaped in the conditions of environment as early as the Palaeogene and Neogene, but the greatest impact on the present-day landscape came from the morphogenetic processes which operated in the Quaternary.Palaeogeographic studies of the analysed area often point to the possible dependencies between the contemporary landscape and its substrate, particularly as regards the valley system. In order to verify this hypothesis, on the basis of archival cartographic materials and a Digital Elevation Model of the current terrain, a procedure for conducting analyses with the use of commonly available GIS tools was proposed. Results of the conducted analysis allow for stating that the major river valleys of Central Poland in large part correspond to the arrangement of the fossil valley system, and the relationships are most easily noticeable for the largest valleys.

Analysis of flooding in urban areas, taking into account the residence time of the water on site case of study: Veracruz, México

Analysing some aspects of water management in urban areas affected by flooding, an event that occurred in September 2010 by overflows Cotaxtla Jamapa and rivers in western Mexico along with the rain event for five consecutive days. In this area, near the Gulf of Mexico, the elevations are less than three meters elevation. Floods are common in cities like Veracruz, in this article the flood risk calculated by means of a hydraulic model of rainfall-runoff dimensional type developed at the Institute of Engineering of the National Autonomous University of Mexico. Data digital terrain elevation models of LIDAR were used, records hourly rainfall levels and channels of some hydrometric stations of the National Water Commission. The location of housing and services in a metropolitan area considered to calculate the depths of flooding in them. To estimate the damage, shall take into account the hydrodynamic behaviour of the flows. Since houses remain flooded for several days, was the reason to use precipitation level for more than seven days. in the mathematical modelling of flows water with a regular grid made up of cells 10 m by side with the boundary condition downstream, corresponding to the predicted change in the average sea level.

Multiple Geotechnological Tools Applied to Digital Mapping of Tropical Soils

ABSTRACT In recent years, geotechnologies as remote and proximal sensing and attributes derived from digital terrain elevation models indicated to be very useful for the description of soil variability. However, these information sources are rarely used together. Therefore, a methodology for assessing and specialize soil classes using the information obtained from remote/proximal sensing, GIS and technical knowledge has been applied and evaluated. Two areas of study, in the State of São Paulo, Brazil, totaling approximately 28.000 ha were used for this work. First, in an area (area 1), conventional pedological mapping was done and from the soil classes found patterns were obtained with the following information: a) spectral information (forms of features and absorption intensity of spectral curves with 350 wavelengths -2,500 nm) of soil samples collected at specific points in the area (according to each soil type); b) obtaining equations for determining chemical and physical properties of the soil from the relationship between the results obtained in the laboratory by the conventional method, the levels of chemical and physical attributes with the spectral data; c) supervised classification of Landsat TM 5 images, in order to detect changes in the size of the soil particles (soil texture); d) relationship between classes relief soils and attributes. Subsequently, the obtained patterns were applied in area 2 obtain pedological classification of soils, but in GIS (ArcGIS). Finally, we developed a conventional pedological mapping in area 2 to which was compared with a digital map, ie the one obtained only with pre certain standards. The proposed methodology had a 79 % accuracy in the first categorical level of Soil Classification System, 60 % accuracy in the second category level and became less useful in the categorical level 3 (37 % accuracy).

ORSADEM: A ONE‐DIMENSIONAL SHALLOW WATER CODE FOR FLOOD INUNDATION MODELLING

ABSTRACTThis paper describes the ORSADEM software, which solves one‐dimensional (1‐D) shallow water equations written in conservative form by numerical schemes suitable for the modelling of shocks and discontinuities generated by a dam break. Unlike the majority of commercial software, ORSADEM automatically defines the model cross‐sections based on the terrain digital elevation model (DEM) and automatically maps the flood‐prone areas, solving the hydraulic equations. The flooded area is mapped using a new method congruent with the unidimensionality of the model. ORSADEM does not need any external platforms. The software has been developed by researchers of the Department of Civil and Architectural Engineering at the University of Pavia and it is presented here applied to the case study of the Brembo River. Copyright © 2013 John Wiley & Sons, Ltd.

Terrain Data Hybrid Entropy Coding Compression Based on Lifting Wavelet and Real-time Rendering

高分辨率地形高程和影像数据给交互式3维地形可视化应用带来沉重压力，主要体现在数据存储、调度传输及实时渲染等方面。该文设计一种基于提升小波变换与并行混合熵编码的地形数据高性能压缩方法，并结合图形处理器(Graphics Process Unit, GPU)Ray-casting实现大规模3维地形可视化。首先建立多分辨率地形块的小波变换模型来映射其求精和化简操作；其次，基于提升小波变换分别构建格网数字高程模型(Digital Elevation Model, DEM)和地表纹理的多分辨率四叉树，对量化后的稀疏小波系数引入并行游程编码与并行变长霍夫曼编码相结合的混合熵编码进行压缩；将压缩数据组织成多序列层进码流进行实时解压渲染。在GPU上基于统一计算设备构架(Compute Unified Device Architecture, CUDA)实现该文的提升小波变换与混合熵编码。实验表明，在压缩比、信噪比与编解码的数据吞吐量综合指标方面，该文方法优于其它类似方法。实时渲染的高帧率满足了交互式可视化的要求。

Evaluation of topographic index in relation to terrain roughness and DEM grid spacing

Topographic index is an important attribute of digital elevation model (DEM) which indicates soil saturation. It is used for estimation of run-off, soil moisture, depth of ground water and hydrological simulation. Topographic index is derived from DEMs; hence the accuracy of DEM influences its computation. Commonly the raster based grid DEM is widely used to simulate hydrological model parameter, and accuracy varies with respect to DEM grid size and morphological characteristics of terrain. In this study topographic index is evaluated in terms of DEM grid size and terrain roughness. The study was carried out on four small watersheds, having different roughness characteristics, located over the Himalayan terrain. Topographic index surface is derived for each watershed from different grid spacing DEM (10–150 m), analysed and validated. It is found that DEM grid spacing affects the topographic index. The surface representation is smooth in the coarse grid spacing and the pattern of topographic index changes with grid spacing. The spatial autocorrelation of topographic index surface reduces when calculated from larger spacing DEM. The mean of the topographic index surface increases and standard deviation decreases with the increase of grid spacing and the effect is more pronounced in the rough terrain. Accuracy of the topographic index is also evaluated with respect to grid spacing and terrain roughness by comparing the topographic index surface with respect to reference data (10 m grid spacing topographic index surface). The RMSE and mean error of topographic index surface increases in larger grid spacing and the effect is more in rugged terrain.

中国地貌区划系统——以自然保护区体系建设为目标

地貌类型是重要的自然地理特征,是影响区域生物多样性空间格局变化的重要因子。地貌研究能使人们深入认识地理环境特点,有利于完善对区域自然环境和地域分异规律的认识,同时对生物地理区划和区域自然保护研究也具有很好的参考价值。采用"自上而下"的区域分割和"自下而上"的区域合并的区划方式,以中国地形DEM作为基础,使用GIS10.0对其进行高程重分类、坡度分析等量化分析,并结合现有气候区划、自然地理区划和地貌类型等资料,对中国地貌格局进行了分析。在考虑生物多样性保护过程中以地貌为主体的地理单元差异性基础上,根据分析结果,提出了以区域自然保护区体系构建为目标的中国地貌区划系统,该地貌区划系统包括了东部季风淋蚀地貌大区、西北干燥风蚀地貌大区、青藏高原高寒冻蚀地貌大区、南海诸岛地貌大区等4个地貌大区,大兴安岭、小兴安岭和内蒙古高原等40个地貌地区,完达山、老爷岭和张广才岭等127个地貌亚地区,以及473个地貌区。其地貌区划方案科学构建了区划等级系统,体现了中国地貌类型的基本特征和分布格局,其中地貌大区基本反映了中国大的地貌格局,地貌地区基本反映了高原、山地、平原等地貌特征的水平分异,地貌亚地区和地貌区基本反映了区域地貌特征。中国地貌区划系统为自然保护区体系构建提供了参考和依据,而且区划界线准确,便于使用。;Given that it is an important natural geographic feature, geomorphic type is an important factor that results in a change in spatial pattern of regional biodiversity. The study of natural landforms can promote greater understanding of geographic environment characteristics. At the same time, the present study has great reference value in the investigation of natural geographic divisions and regional nature conservation research. It is also conducive to improvement of the understanding of the natural environment and differentiation in a region. In the present study, the landscape pattern of China was analysed using a qualitative and quantitative approach, based on data of the terrain digital elevation model. We then determined a geomorphologic regionalization system for the country. In the course of analysis, relative consistency, completeness and hierarchical division were the guiding principles. Further, the methods of top down regional segmentation and bottom up regional merger were used. Through a quantitative analysis using GIS10.0 software, we obtained the outcomes of reclassification of elevation, slope analysis, and others. According to the result and the data of climate regionalization, natural geographic regionalization, geomorphic types and others, the geomorphologic regionalization system of the country is proposed, which is aimed at construction of a regional nature reserve system and biodiversity protection. This geomorphologic regionalization system included four geomorphologic zones (the eastern monsoon rain erosion geomorphologic zone, the northwest dry wind erosion geomorphologic zone, Qinghai-Tibet Plateau high frost weathering geomorphologic zone, and the South China sea islands geomorphic zone), 40 geomorphologic areas (for example the Da Xing'an Mountains, Inner Mongolia Plateau, and the Xiao Xing'an Mountains), 127 geomorphologic subareas (for example Wandashan, Laoyeling, and Zhangguangcailing), and 473 geomorphologic regions. The division level of the geomorphologic regionalization system was scientifically constructed, and reflects the basic features of geomorphic distribution. The geomorphologic zone reflects the diverse landscape pattern of China. The geomorphologic area reflects the horizontal differentiation features of plateaus, mountains, and plains. The geomorphologic subarea and geomorphologic region indicate regional geomorphic characteristics. It is difficult to use mathematical methods to directly determine morphological differences, on account of the complexity of natural geographic features. However, the results of quantitative analysis can be used as a reference for qualitative analysis. The features of geomorphologic regionalization system are listed as follows: (1) The South China Sea, which has unique climate characteristics and geological geomorphologic features, was distinguished as an independent zone. (2) Given the intent of constructing the nature reserve system, there is a substantial difference with other geomorphologic regionalization. Further, our regionalization system appears to be more scientific and accurate, as well as having greater definition. Thus, the system can be used as the basis of natural conservation geographic regionalization, and provides a reference and foundation for the construction of a nature reserve system. (3) Our system is easier to understand and master, using the usual naming convention in the geomorphologic system. (4) Large quantities of topographic data and an advanced geographic information technology were used to ensure the objectivity and scientific integrity of the results.

A reflectivity climatology algorithm for hybrid scans and its application to radar coverage over the Tibetan Plateau

The traditional algorithm for hybrid radar scans uses standard terrain digital elevation model (DEM) data and the latitudes, longitudes and altitudes of contributing radar stations. While radar station location information is often inaccurate, signal blockages due to trees, buildings, and other surface objects are not included in the DEM data. Accordingly, hybrid scan elevations derived using this traditional algorithm are prone to errors. Here, reflectivity climatology data (the frequency of occurrence of reflectivity) are used to improve the algorithm for hybrid scans. Three parameters are introduced, then applied to evaluation of signal blockage for every radar bin using a fuzzy logic technique. This new algorithm provides an improved determination of the lowest unblocked elevation for hybrid scans. The new algorithm is validated by examining the scope and continuity of the calculated hybrid scan reflectivity in a case study, and the performance of this climatology-based algorithm is evaluated relative to the traditional terrain-based algorithm. The climatology-based hybrid scans are then used to examine the spatial coverage provided by the operational weather radar network over the Tibetan Plateau. The results indicate that the terrain-based hybrid scan algorithm introduced errors that caused obvious V-shaped gaps in hybrid scan reflectivity. By contrast, the climatology-based hybrid scan algorithm more accurately determined the lowest unblocked elevation and reduced the impacts of blockage. The coverage map illustrates the limitations of the weather radar network over the Tibetan Plateau. These limitations inhibit the usefulness of the radar data. Additional radar or observational data are needed to fill these gaps and minimize the impacts of signal blockage.

PROGRESSIVE DENSIFICATION AND REGION GROWING METHODS FOR LIDAR DATA CLASSIFICATION

Abstract. At present, airborne laser scanner systems are one of the most frequent methods used to obtain digital terrain elevation models. While having the advantage of direct measurement on the object, the point cloud obtained has the need for classification of their points according to its belonging to the ground. This need for classification of raw data has led to appearance of multiple filters focused LiDAR classification information. According this approach, this paper presents a classification method that combines LiDAR data segmentation techniques and progressive densification to carry out the location of the points belonging to the ground. The proposed methodology is tested on several datasets with different terrain characteristics and data availability. In all case, we analyze the advantages and disadvantages that have been obtained compared with the individual techniques application and, in a special way, the benefits derived from the integration of both classification techniques. In order to provide a more comprehensive quality control of the classification process, the obtained results have been compared with the derived from a manual procedure, which is used as reference classification. The results are also compared with other automatic classification methodologies included in some commercial software packages, highly contrasted by users for LiDAR data treatment.

Constructing DEM Based on InSAR and the Relationship between InSAR DEM's Precision and Terrain Factors

In this paper, taking the ENVISAT satellite SAR images in Bam city as an example, the authors construct Digital Elevation Model (DEM) with InSAR technology, and by comparing the InSAR DEM with SRTM-3 DEM they also research the relationship between InSAR DEM's precision and terrain factors represented by slope and aspect. The results show that the elevation difference mean error between InSAR DEM and SRTM-3 DEM of the experiment area is 12.50 meters, and the precision is reduced with the increase of slope but basically has nothing to do with aspect. In this paper, taking the ENVISAT satellite SAR images in Bam city as an example, the authors construct Digital Elevation Model (DEM) with InSAR technology, and by comparing the InSAR DEM with SRTM-3 DEM they also research the relationship between InSAR DEM's precision and terrain factors represented by slope and aspect. The results show that the elevation difference mean error between InSAR DEM and SRTM-3 DEM of the experiment area is 12.50 meters, and the precision is reduced with the increase of slope but basically has nothing to do with aspect.

Green Network Planning of Single Frequency Networks

This paper investigates the network deployment of single frequency networks (SFN) based on OFDM schemes that are standardized for terrestrial broadcasting systems, for digital audio broadcasting (DAB) and for digital video broadcasting (DVB) systems. The concept of green network planning is presented. The term `green' refers to low carbon, energy efficiency and low exposure to radiation, parameters important for the sustainable growth. For the purpose of our investigation a mountainous area of Northern Greece is examined, that is described by a digital terrain elevation model (DTEM) and field computations are based on multi shape slope uniform theory of diffraction (UTD) technique. A genetic algorithm (GA) optimization method is developed for the network planning purposes. A comparison between various planning strategies is presented. It is shown that great CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> reductions, cost savings and low exposure to radiation can be achieved when the network planning considers a `green' strategy.

Grid-based Hydrostratigraphic 3D Modelling of the Quaternary Sequence in the Chateauguay River Watershed, Quebec

Groundwater recharge, groundwater-surface water interaction, and protection and management of the groundwater resource are strongly constrained by the geological nature of the substratum. A grid-oriented technique has been developed in order to build a 3D stratigraphic model of the Quaternary sediments overlying a regional fractured rock aquifer. The technique is based on the integration of the surficial sediments map and borehole logs with the use of GIS and grid-calculator software Vertical Mapper. The applied methodology focused on estimating the thickness of the stratigraphic units rather than the elevation of the contacts. First, a regular grid was generated over the study area with 30 × 30 m cells. The bulk thickness of the Quaternary sequence for each grid cell was computed as the difference between the terrain digital elevation model and the rock surface krigged over more than 5000 drillers’ logs available. Two computation methods for estimating the discrete thicknesses are discussed and evaluated: the absolute method, in which the thickness of a given unit is computed as an independent value, and the relative method, in which the thickness is computed as a fraction of the bulk thickness. The simplified Quaternary stratigraphy consists, from top to bottom, of: organics (peat), alluvium, lacustrine, aeolian, coarse marine, marine clay and fine silt, fine sandy and silty glacio-fluvial, coarse sandy and gravelly glacio-fluvial, and glacial (silty clayey till) sediments. Their spatial distribution respects fully the surficial sediments map and contacts. At locations with missing stratigraphic data, the borehole logs database was improved with the addition of control points representing the anticipated variation of the successive layers. With the absolute method, derivation of the thicknesses of the layered strata in zones of irregular bedding proved to be difficult. The relative computation method gives more consistent results for various stratigraphic settings and allows rapid, internally consistent estimation of the overburden stratification.

Based on Delaunay Triangulation DEM of Terrain Model

Digital Terrain Model (Digital Terrain Model acronym DTM) is arbitrary use of a large number of coordinates in three-dimensional x, y, z coordinates of the point on the ground for a form of Statistics said that the terrain surface morphology is the number of attribute information is a space location characteristics and attributes of the terrain described the figures, initially for the automatic design of highway proposed. With the world of computer technology and the rapid development of 3-D visualization technology into the traditional static two-dimensional map of the three-dimensional terrain modeling makes a Geographic Information System (GIS) and digital mapping, a new field of study. DTM is the basis of geographic information system data, mainly used to describe the ground state of ups and downs, the terrain can be used to extract various parameters such as slope, aspect, roughness, and Visibility analysis, watershed generation applications such as structural analysis. Therefore, the DTM in land use analysis, and rational planning, forecasting flood danger, as well as military navigation and missile guidance systems, and combat electronic sand table, and other fields are widely used. Digital Terrain Elevation Model mainly contains the attributes of surface morphology, as well as other attributes, such as slope, aspect and so on. Terrain Elevation attribute is the basis of the model attributes, other elements of the terrain elevation attributes can be directly or indirectly receive, digital elevation model (Digital Elevation Model, acronym DEM) acts as a digital terrain on the main study. DEM is that the number of regional terrain, elevation Z coordinates on the plane X, Y, the two variables of continuous function of a limited discrete said, a series of ground from the X, Y location and elevation linked by some Organization structure with the actual terrain features that the spatial distribution model, it is a spatial information system an important component part.

Computation of the space and time evolution of equilibrium-line altitudes on Andean glaciers (10°N–55°S)

A previous study of Fox [Fox, A.N. 1993. Snowline altitude and climate at present and during the Last Pleistocene Glacial Maximum in the Central Andes (5°–28°S). Ph.D. Thesis. Cornell University.] showed that for a fixed 0 °C isotherm altitude, the equilibrium-line altitude (ELA) of the Peruvian and Bolivian glaciers from 5 to 20°S can be expressed based on a log–normal expression of local mid-annual rainfall amount ( P). In order to extrapolate the function to the whole Andes (10°N to 55°S) a local 0 °C isotherm altitude is introduced. Two applications of this generalised function are presented. One concerns the space evolution of mean inter-annual ELA for three decades (1961–1990) over the whole South American continent. A high-resolution data set (grid data: 10′ for latitude/longitude) of mean monthly air surface temperature and precipitation is used. Mean annual values over the 1961–1990 period were calculated. On each grid element, the mean annual 0 °C isotherm altitude is determined from an altitudinal temperature gradient and mean annual temperature ( T) at ground level. The 0 °C isotherm altitude is then associated with the annual precipitation amount to compute the ELA. Using computed ELA and the digital terrain elevation model GTOPO30, we determine the extent of the glacierised area in Andean regions under modern climatic conditions. The other application concerns the ELA time evolution on Zongo Glacier (Bolivia), where inter-annual ELA variations are computed from 1995 to 1999. For both applications, the computed values of ELA are in good agreement with those derived from glacier mass balance measurements.

Using the roadeng system to design an optimum forest road variant aimed at the minimization of negative impacts on the natural environment

The optimization study was carried out in the part of the Jeseníky Mts. region in order to find the optimum variant of a forest road route. The ROADENG system was used for determining the Jezerná forest road design with use of projection above the digital elevation model of terrain. Particular variants of the forest road route were calculated and analyzed on the basis of environmental approach. The final report recommended one of the variants for the final elaboration of project documentation and for construction.

Evaluation on the accuracy of digital elevation models

There is a growing interest in investigating the accuracy of digital elevation model (DEM). However people usually have an unbalanced view on DEM errors. They emphasize DEM sampling errors, but ignore the impact of DEM resolution and terrian roughness on the accuracy of terrain representation. This research puts forward the concept of DEM terrain representation error (Et) and then investigates the generation, factors, measurement and simulation of DEM terrain representation errors. A multi-resolution and multi-relief comparative approach is used as the major methodology in this research. The experiment reveals a quantitative relationship between the error and the variation of resolution and terrain roughness at a global level. Root mean square error (RMS Et) is regressed against surface profile curvature (V) and DEM resolution (R) at 10 resolution levels. It is found that the RMS Et may be expressed asRMS Et=(0.0061·V+0.0052)·V+0.2415. This result may be very useful in forecasting DEM accuracy, as well as in determining the DEM resolution related to the accuracy requirement of particular application.

Key issues in image understanding in remote sensing

Remotely sensed images of a planet’s atmosphere, oceans and surface contain a plethora of confusing signals about the physical nature of these phase states. Historically, there has been an emphasis on the semi-automated extraction of feature classes based on the spectral properties of objects viewed within a scene and on the use of ad hoc manual photointerpretation techniques. Although these approaches will remain important, they are inadequate, on grounds of speed, accuracy and cost, for the increasing demands of data-gatherers and consumers. Research has recently begun into the automation of image-interpretation tasks and the development of parallel machines with the required processing capabilities. Three important requirements are: (i) means to simulate the appearance of a scene, including the interaction of electromagnetic radiation with the surface and the effects of any intervening atmosphere; (ii) an understanding of how knowledge can be captured and introduced at different levels in the processing hierarchy and (iii) the application of constraints based on a knowledge of the geometry of objects in the scene. These three aspects will be illustrated by examples from various fields, including petroleum exploration, measurement of fluid motion and the extraction of digital terrain elevation models.

Multiple Incidence Angle SIR-B Experiment Over Argentina: Generation of Secondary Image Products

Original radar images may be geometrically and radiometrically distorted. This may be a particular problem when multiple angle imagery is analyzed and there is topographic relief in the area of interest. This paper describes a set of techniques designed to combine a multiple angle radar data set with a digital terrain elevation model, to generate a set of new images called secondary image products. These new images are geometrically rectified radar ortho-images, radiometrically rectified images, and stereo ortho-images. These secondary images can then reliably be used for thematic interpretation.