Use Of Digital Elevation Models Research Articles

Use of HAND terrain descriptor for estimating flood-prone areas in river basins

The flood hazard mapping in a river basin is crucial for flooding risk management, mitigation strategies, and flood forecasting and warning systems, among other benefits. One approach for this mapping is based on the HAND (Height Above Nearest Drainage) terrain descriptor, directly derived from the Digital Elevation Model (DEM), in which each pixel represents the elevation difference of this point in relation to the river drainage network to which it is connected. Considering the Mamanguape river basin (3,522.7 km²; state of Paraíba, Brazil) as the study location, the present research applied this method and verified it as for five aspects: consideration of a spatially variable minimum drainage area for denoting the river drainage initiation; the impact of considering a depressionless DEM; evaluation of hydrostatic condition; effect of incorporating an existing river vector network; and comparative analysis of basin morphology regarding longitudinal river profiles. According to the results, adopting a uniform minimum drainage area for the river network initiation is a simplification that should be avoided, using a spatially variable approach, which influences the amount and spatial distribution of flooded areas. Additionally, considering the depressionless DEM leads to higher values of HAND and to a smaller flooded area (difference ranging between 3% and 99%), when compared with the use of DEM with depression, despite 3.1% of the pixels representing depressions. The use of the depressionless DEM is recommended, whereas the DEM pre-processing by incorporating a vector network (stream burning) generates dubious results regarding the relation between HAND and the morphological pattern presented in the DEM. Moreover, the estimation of flooded areas based on HAND does not guarantee the hydrostatic condition, but this disagreement comprises a negligible area for practical purposes.

Mapping of the current state of forest vegetation in the north Baikal Region based on the merging of remote sensing data and ground observations

Geoinformation analysis and modeling study of the current state of vegetation (as exemplified by the southeastern macroslope of the Baikal Range, Eastern Siberia) were performed. The phytocenoses of the territory differ from each other in many features, namely in projective cover, ratio of ecological groups, confinement to landforms, epiterranean phytomass, etc. These details help to interpret the types of plant communities based on the values of the calculated vegetation index. We proposed a technique that assumes the joint use of the NDVI and NDWI indices, a digital elevation model (DEM) based on SRTM radar topographic survey data, forest inventory data and materials from field expeditions. The use of the DEM and the indices reflecting the physiological state of vegetation considering their availability of chlorophyll and water helps to arrange the communities under study into groups determined by moisture conditions and biomass supply. To determine the species composition of forest stand, we proposed a method based on the Boolean logic-a decision tree-a schematic representation in the form of a tree structure of a complex decision-making process used in a multi-step analysis. The results obtained show that the use of the relationship between the ratio of plant communities to the moisture factor and their spectral characteristics, taking into account the use of DEMs, enables us to create very informative maps, to improve the reliability of interpretation of satellite information, and to map territories not covered by ground-based surveys with the use of interpolation.

Геоинформационные карты рельефа Северо-Востока Азии как основа изучения морфологии речных бассейнов

Цель. Создать первые геоинформационные карты горного рельефа Северо-Востока Азии и получить на этой основе морфологические характеристики водосборов, как имеющихся в информационных источниках, так и новых с оценкой точности и уровня корреляционных связей между ними. Материалы и методы. На их основании сравнительного анализа методов количественной морфометрии рельефа Северо-Востока Азии (аэрофотоснимки, карты, ГИС технологии) установлена перспективность расширения информационной базы с помощью геоинформационных карт. Применение цифровых моделей рельефа наиболее важно для слабо изученных бассейнов малых рек, данные о которых отсутствуют в справочно-фондовых источниках. Выбранная универсальная программа ArcGIS, версии 10.4, дает возможность получить так же принципиально новые параметры водосборных площадей горных рек. В связи с этим цифровая карта с высотными отметками рельефа земной поверхности (SRTM) и послужила исходным материалом для расчета различных морфометрических характеристик водосборов (например, площади и средние высоты водосборов, длину водотоков и т. д.). Результаты и обсуждение. Статистический анализ величин площадей водосборов, на основе геоинформационных карт (программа ArcGIS, версия 10.4) и растровых аналогов свидетельствует о незначительном их отличии (–3.9 to +3.0 %). Показана перспективность применения цифровых моделей рельефа для получения совершенно новых характеристик бассейнов рек, отсутствующих в известных источниках информации (например, форм, периметров, уклонов средних высот, и. т. д.). Кроме того, на основе статистического анализа дана оценка параметров различных водосборов и их частей (верховье, низовье), например, неоднородность поверхности долин рек и водоразделов. В дополнении указанном выше, установлена тесная, или, в отдельных случаях, функциональная связь между некоторыми характеристиками водосборов (например, уклоны – средние высоты). Выводы. Построенные впервые цифровые модели горного рельефа Северо-Востока Азии (программа ArcGIS, версия 10.4) позволили с достаточной точностью вычислить основные морфометрические параметры водосборов рек. Использование цифровых карт с высотами земной поверхности, в частности, SRTM, дали возможность получить принципиально новые, по сравнению с имеющимся уровнем изученности, параметры бассейнов водотоков, необходимые для науки и практики.

Digital Elevation Models of the Bottom in the Operational Oceanography System

A new area of oceanography, operational oceanography, involves a comprehensive assessment and forecast of the variability of the state of the marine environment. This requires systematic study of numerous natural parameters, the creation of integrated measurement systems for the properties of the water column and seafloor, rapid data collection and transmission systems, assimilation of new data in the model, etc. The seafloor has a significant impact on the hydrophysical state of the environment and vice versa; accordingly, information is needed on the state and properties of the bottom in the deployment area of various surveillance tools, including assessment of possible geohazards. The spatial distribution and possible variability of the geomorphological and geological–geophysical parameters of the bottom, which determine the geoacoustic properties, depends on the shape of the relief and its morphometric characteristics. Thus, the digital elevation model (DEM) is an essential component of marine geographic information systems and an essential element of operational oceanography. A DEM entails an organized structure of files containing vector representations of various types of spatial objects, information on their attributes, and topological relationships between them. The DEM displays the seafloor relief as a grid file with a resolution corresponding to a given scale. Methods for the direct spatial mathematical processing of DEMs make it possible to obtain a wide range of bottom surface characteristics, including morphometric. DEMs can have both independent practical application and act as parameters for systematizing, typifying, and zoning the seafloor. The paper outlines some areas of the possible use of DEMs in operational oceanography with a case study of the Arctic shelf.

Digital Elevation Models for topographic characterisation and flood flow modelling along low-gradient, terminal dryland rivers: A comparison of spaceborne datasets for the Río Colorado, Bolivia

Many dryland rivers are terminal systems, with small channels undergoing prominent downstream size reductions before ending on channelless floodplains, in wetlands, or at playa margins. Spaceborne Digital Elevation Models (DEMs) provide potential for assessing subtle topographic and hydrodynamic changes in these low-gradient, low-relief settings, but challenges are posed by limitations in vertical and horizontal accuracy. This study evaluates the use of different spaceborne DEMs for topographic characterisation and flood flow modelling of the low-gradient (<0.0006 m m−1) Río Colorado terminal system, Bolivia. A comparison between DEM and field dGPS elevation data (1290 measurement points) reveals that the TanDEM-X DEM 12 m (TDX-12 m) has a RMSE of 0.47 m, far less than those of other frequently used spaceborne DEMs such as ALOS RTC (4.58 m) and SRTM (6.02 m). For hydrodynamic modelling, TDX-12 m data were smoothed (adaptive filter and feature-preserving DEM smoothing) and upscaled. The smoothed TDX-12 m data were mosaiced with a dGPS data-derived river path, surveyed along a reach (mean width <30 m) with a prominent downstream size decrease. The methods enabled effective de-noising of the TDX-12 m data (RMSE 0.29 m) and resulted in a high linear regression correlation coefficient (0.75). HEC-RAS 2D modelling reveals that in the selected reach, overbank flooding starts in the downstream part when discharge is <18 m3/s, with flow initially spreading through crevasse channels and levee topographic lows. As discharge increases, flow spreads farther across the floodplain, ultimately forming connected floodplain flow in distal topographic lows. Satellite imagery and a derived water index indicate the same floodplain flow patterns as the modelling (critical success index 0.77). Wider use of DEMs based on TDX-12 m data for topographic characterization and flood flow modelling along relatively small, low-gradient terminal dryland rivers will result in many scientific and applied benefits.

The use of digital elevation models for detailed mapping of slope soils

Formulation of the problem. The current stage of agricultural development in Ukraine requires highly informative soil maps. One of the directions for creating such maps is the use of digital elevation models (DEM) as a spatial translator of soil characteristics. The literary review has showed that despite the large volume of publications on this topic, a number of issues of soils digital mapping remain relevant. The purpose of the article is to study the possibilities of using relief-ground indicative models in creation of detailed digital ground maps. Methods. The research was conducted on the territory of the testing ground. During the field study of the landfill, it has been established that the soils are represented by chernozem typical of varying erosion degrees. It is proposed to use a xeromorphism coefficient for the quantitative account of the landforms influence on soil formation, characterizing changes in hydrothermal conditions for a particular section of the topography, compared with the horizontal surface. A detailed DTM was obtained, using the "Phantom 3" UAV.The derivative models of a number of topographic parameters were built on its basis later. A digital model of xeromorphism of the territory was built, transformed into a model of organic carbon (C) content. The specified map shows initial conditions of the soil cover. It can be used as a standard to compare parameters of modern soils for assessment of extent of their degradation. Comparison of this map with the map of actual C content has shown that average loss of C by soils of the studied area owing to anthropogenic degradation can be estimated at 5.1 kg on 1 t of the soil. Results. Investigations have proved that the geoinformation analysis of landforms allows to quantitatively shape hydrothermal conditions of soil formation for a certain territory. The cartographic materials constructed on such a methodical approach characterize landscape potential on soil formations and reflect quasi-virgin land condition of the soil. Scientific novelty and practical significance. The detailed soil maps, based on the results of field and laboratory soil studies, leading to potential soil assessment for DEM analysis in the article, allow to adequately estimate and objectively represent distribution of eroded and xeromorphic soils and their complexes on sloping lands.

Implications of Different DEMs on Watershed Runoffs Estimations

Watershed modelling tools like ArcSWAT, an ArcGIS extension of Soil and Water Assessment tool (SWAT), are useful to watershed managers in many ways. One particular use is analyzing model outputs for decision making related to waterway restoration and mitigation, which is often undertaken to improve water quality in streams. The present study evaluates the use of digital elevation model (DEM) at 10 meter, 30 meter, and 100 meter pixel size on non-point runoff predictions for three sub-watersheds in Raritan River Basin in New Jersey. These three watersheds include: Bound Brook, Lamington River, and Lawrence Brook watersheds. ArcSWAT is utilized to investigate the difference due to DEM variation in predicting monthly estimates of pollutant loads including ammonium (NH4), nitrite (NO2) and sediment transported with water out of a watershed. Using land use/cover, slope and soil data for 2012, monthly pollutant loads are calculated for each sub-basin in the watershed over a 10-year simulation period (2012-2022) in ArcSWAT. Overall statistical and spatial results show that ArcSWAT results are sensitive to changes in DEM pixel size for watershed modeling. The results show that total sum of monthly runoffs including NH4, NO2 and sediment differ among the three different DEMs. Moreover, the spatial pattern of input (in sub-catchments) also changes among the three DEMs for most watersheds. This indicates that watershed managers need to supplement model predictions with field measurements before making substantial investments in stream restoration programs.

Principles of construction of elevation maps for land navigation

This article provides an overview of the basic principles of elevation maps for land navigation, in particular through the use of SRTM data. The relevance of research is the daily use of digital elevation models in various spheres of human life. At present, digital elevation models are subject to strict accuracy requirements. A lot of research is aimed at methods to improve the accuracy of digital elevation models

Evaluation of morphometric parameters using geographic information system coupled with digital elevation model: A case study from Gumara watershed, Ethiopia

AbstractEvery year during the monsoons, water‐activated soil erosion poses serious spatial–environmental tribulations, causing heavy damage to agricultural lands and sedimentation in reservoirs, creating water quality problems in nearby surface water bodies. A digital elevation model (DEM) and geographic information system (GIS) are coupled to investigate the various morphometric parameters and their hydrological implications. The software used to perform the overall analysis is the ESRI ArcGIS v10.3.1 with the ESRI Spatial Analyst and ArcHydro extension. Morphometric examination plays a vital role in watershed planning. For example, stream power index (SPI) analysis helps in delineating the areas prone to erosion. The zones with high values of SPI demand conservation measures in the Gumara watershed, Ethiopia. The general outcomes demonstrate that the use of DEM combined with GIS provide potentially powerful tools to analyze morphometric parameters for watershed management.

Yakacık Çayı Havzasının (Hatay) Morfometrik Analizi

Bu çalışmada, Coğrafi Bilgi Sistemleri kullanılarak sayısal yükseklik modelleri üzerinden havza morfometrik özelliklerinin belirlenmesi amaçlanmıştır. Morfometrik analizler havzanın rölyefe ait çizgisel, alansal özelliklerini içermektedir. Çalışma alanı olarak Yakacık Çayı Havzası (Hatay) seçilmiştir. Havzanın morfometrik karakteristiğinin belirlenmesinde 1/25.000 ölçekli sayısal topografik haritalar üzerinden Sayısal Yükseklik Modeli üretilmiş, morfometrik analizlerin ve indis hesaplarının tamamı Coğrafi Bilgi Sistemleri ortamında ArcGIS 10.2 yazılımında otomatik türetilmiştir. Bu bağlamda havza karakteristik özelliklerinden; havza sınırı, alanı, çevresi, akış yönleri, drenaj ağları, eğim ve bakı gibi özellikleri belirlenmiştir. Sayısal topografik harita üzerinden klasik yöntemlerle belirlenmesi zor ve zaman alıcı olan havza sınırlarının ve gerekli morfolojik özelliklerinin Coğrafi Bilgi Sistemleri yardımıyla oluşturulacak sayısal yükseklik modeli kullanılarak daha kolay ve hızlı bir şekilde yapılabileceğine ilişkin yaklaşımlar ortaya konulmuştur.

Use of DEMs Derived from TLS and HRSI Data for Landslide Feature Recognition

This paper addresses the problems arising from the use of data acquired with two different remote sensing techniques—high-resolution satellite imagery (HRSI) and terrestrial laser scanning (TLS)—for the extraction of digital elevation models (DEMs) used in the geomorphological analysis and recognition of landslides, taking into account the uncertainties associated with DEM production. In order to obtain a georeferenced and edited point cloud, the two data sets require quite different processes, which are more complex for satellite images than for TLS data. The differences between the two processes are highlighted. The point clouds are interpolated on a DEM with a 1 m grid size using kriging. Starting from these DEMs, a number of contour, slope, and aspect maps are extracted, together with their associated uncertainty maps. Comparative analysis of selected landslide features drawn from the two data sources allows recognition and classification of hierarchical and multiscale landslide components. Taking into account the uncertainty related to the map enables areas to be located for which one data source was able to give more reliable results than another. Our case study is located in Southern Italy, in an area known for active landslides.

The application of LiDAR-based DEMs on WWII conflict sites in the Netherlands

Airborne Laser Scanning or Light Detecting And Ranging (LiDAR) is quite a new technique for most archaeologists. Digital Elevation Models (DEMs), derived from the LiDAR-data, can be very useful to map archaeological sites in order to get a better overview of what is left and how these remains should be protected and researched further. LiDAR-based DEMs can be extremely useful to conflict archaeologists, especially in the Netherlands where excavation of the remains of World War II (WWII) is often problematic. Using DEMs it is possible to make both an indication of the archaeological and the heritage value of a conflict site. The use of DEMs will improve the prospection, mapping and monitoring of archaeological sites.

APPLICATION OF DSM IN OBSTACLE CLEARANCE SURVEYING OF AERODROME

Compared to the wide use of digital elevation model (DEM), digital surface model (DSM) receives less attention because that it is composed by not only terrain surface, but also vegetations and man-made objects which are usually regarded as useless information. Nevertheless, these objects are useful for the identification of obstacles around an aerodrome. The primary objective of the study was to determine the applicability of DSM in obstacle clearance surveying of aerodrome. According to the requirements of obstacle clearance surveying at QT airport, aerial and satellite imagery were used to generate DSM, by means of photogrammetry, which was spatially analyzed with the hypothetical 3D obstacle limitation surfaces (OLS) to identify the potential obstacles. Field surveying was then carried out to retrieve the accurate horizontal position and height of the obstacles. The results proved that the application of DSM could make considerable improvement in the efficiency of obstacle clearance surveying of aerodrome.

APPLICATION OF DSM IN OBSTACLE CLEARANCE SURVEYING OF AERODROME

Abstract. Compared to the wide use of digital elevation model (DEM), digital surface model (DSM) receives less attention because that it is composed by not only terrain surface, but also vegetations and man-made objects which are usually regarded as useless information. Nevertheless, these objects are useful for the identification of obstacles around an aerodrome. The primary objective of the study was to determine the applicability of DSM in obstacle clearance surveying of aerodrome. According to the requirements of obstacle clearance surveying at QT airport, aerial and satellite imagery were used to generate DSM, by means of photogrammetry, which was spatially analyzed with the hypothetical 3D obstacle limitation surfaces (OLS) to identify the potential obstacles. Field surveying was then carried out to retrieve the accurate horizontal position and height of the obstacles. The results proved that the application of DSM could make considerable improvement in the efficiency of obstacle clearance surveying of aerodrome.

Piezometry mapping accuracy based on elevation extracted from various spatial data sources

Any hydrogeological conceptual model of an aquifer requires a piezometric map to enable defining flow direction, hydraulic gradient, groundwater recharge and discharge zones. Thus, the piezometric head calculation requires an accurate assessment of the elevation and the depth to water in monitoring wells. The main concern of aquifer managers remains the elevation estimate with a satisfactory accuracy, particularly in developing countries, where a lack of well surveying data is frequently encountered. A solution to this situation may be found in the use of digital elevation models (DEMs). In the present paper, a methodology to extract well elevations from DEMs based on datasets from Shuttle Radar Topography Mission (SRTM), Google Earth and digitized topographic map is presented. Statistical analyses of the elevations derived from a topographic field survey and the relative DEMs and piezometric map comparisons are used to assess the elevation accuracy. The DEM generated from the topographic map (TopoDEM) resulted in the closest match to the surveyed one with a correlation coefficient of 0.98 and a root mean square error of 0.76. The elevation from SRTM and Google Earth DEMs lead to an underestimation of the piezometry with the poorest performance from Google Earth DEM.

LIDAR-based roadway and roadside modelling for sight distance studies

Sight distance is a key aspect of road design and operation because of its relationship to traffic safety. The most realistic procedures for calculating the section of roadway visibility to the driver require the use of digital elevation models (DEM), which represent both the roadway itself and the features along the roadside. In this study, the influence of different types of DEM, an essential asset in sight distance analysis, is evaluated. Digital terrain models (DTMs), which represent the bare ground surface, and digital surface models (DSMs) that also consider elements above the terrain have been utilised. Both are high-resolution models obtained through airborne Light Detection and Ranging (LIDAR) or terrestrial vehicle (Mobile Mapping System, MMS). In addition, this study shows the influence of roadside vegetation on sight distance, revealing the underlying difficulties and suggesting possible solutions for sight distance studies when using these models.

Detection of Flood Hazard in Urban Areas Using GIS: Izmir Case

The aim of this study is to predict the potential flood-hazard areas using Shuttle Radar Topography Mission - Digital Elevation Model (SRTM-DEM). The study area is the province of Izmir. SRTM-DEM of the Izmir Province has 90 m of grid size resolution; 45 m of horizontal accuracy; and 15 m of vertical accuracy. Within this study, obtaining spatial information on flood-hazard by using Izmir digital terrain models and by 3D analysis that will help to achieve the regional flood hazard management scheme is aimed. Flood-hazard areas have been identified by the use of digital elevation model covering the study area. The main rivers in the study area are Gediz, Kucuk Menderes and Bakircay that creates the coastal flood plains. In order to estimate the spatial distribution of flood-hazard areas in İzmir, five factors are used: flow accumulation, land use, slope, rainfall intensity, and elevation. The classic hydrological modelling approach was applied to determine the rainfall intensity; rainfall intensity of study region is created with the average amount of total rainfall intensity of fifteen stations in the two basins per minute using the interpolation method (spline interpolation). By the digitizing rivers, topography, flow direction and flow accumulation, as well as the flood detention areas are determined. These factors were combined with the weighted overlay method to determine categorized flood-hazard areas. As a result, possible flood-hazard areas have been determined in the case of Izmir Province.

High-resolution Modelling With Bi-dimensional Shallow Water Equations Based Codes – High-Resolution Topographic Data Use for Flood Hazard Assessment Over Urban and Industrial Environments

The availability of new generation of High-Resolution (HR) topographic datasets combined with high performance computing resources opens the door to HR hydraulic simulations for risk assessment. LiDAR and photo-interpreted datasets are promising for HR Digital Elevation Model (DEM) generation, allowing inclusion of fine (infra-metric) aboveground structures influencing overland flow hydrodynamic in urban environment. Nonetheless, if topographic data is one key input for free surface hydraulic modelling using standard 2D Shallow Water Equations (SWEs) based codes, several categories of technical and numerical challenges arise to use HR dataset within numerical modelling. This proceeding explores the new possibilities, advantages and limits of HR topographic data use with 2D SWEs based numerical modelling tools for flood hazard assessment and proposes an original method for uncertainty assessment. The concepts of HR topographic data and 2D SWE based numerical modelling are reviewed. Using LiDAR and photo-interpreted datasets, different 2D SWEs based codes (Mike 21, Mike 21 FM, TELEMAC-2D, FullSWOF_2D) and strategies are tested to encompass HR DEM in intense rainfall and river flood events simulations ranging from industrial site scale to a megacity district scale (Nice, France). Tools and methods for assessing uncertainties related to HR DEM use with 2D SWE based codes are developed to perform a spatial global sensitivity analysis related to HR topographic data use. Computed sensitivity indices maps quantify the importance and spatial variability of uncertainties introduced by modeller choices regarding ways HR topographic information are integrated in models, compared to measurement errors. Impact of thin aboveground features inclusion, even at a decreased resolution, appears as a crucial asset in flood risk assessment on urban area, but requires providing caution to decision makers along with models’ results.

An Error Budget for Mapping Field-Scale Soil Salinity at Various Depths using Different Sources of Ancillary Data

To manage soil salinity, farmers need to map its variation, often quantified as the electrical conductivity of a saturated soil-paste extract (ECe, dS m-1). However, ECe determination is time-consuming and expensive. Previous studies have evaluated the use of digital elevation models (DEMs, i.e., elevation), airborne γ-ray (γ-ray) spectrometry (i.e., K, U, and Th) and electromagnetic (EM, i.e., EM38 and EM34) data to map ECe at the district scale. Herein we use similar ancillary data set and empirical best linear unbiased prediction (E-BLUP) to make maps of ECe at different depth intervals (0–0.25, 0.25–0.50, and 0.50–0.75 m) at the field scale. The ancillary data was collected using a ground-based mobile sensing system which included; a GPS which provided spatial coordinates (Easting, Northing), a RS700 (γ-ray) mobile spectrometer, and a DUALEM-1. An error budget procedure was conducted to quantify the model, input, and individual covariate errors of ECe. Results show that while none of the γ-ray data were significant, scaled Easting, elevation, and 1-m horizontal coplanar (1mHcon) were optimal for mapping ECe at 0 to 0.25 m, while 1mHcon was optimal at 0.25 to 0.50 m and 0.50 to 0.75 m. Among all the individual covariate errors for mapping 0- to 0.25-m ECe, elevation (0.40 dS m-1) was smallest, followed by 1mHcon (2.23 dS m-1). To reduce error, additional soil samples are necessary to prevent the edge effect of the kriging process. Additionally, inversion of EM data could be used to improve ECe mapping considering the relatively large model error associated with EM data in the subsoil of inverted salinity profiles.

A fast topographic characterization of seismic station locations in Iran through integrated use of digital elevation models and GIS

Ministry of Education, Culture, Sports, Science and Technology of Japan with Grant-in-Aid for Scientific Research (B), No. 25289139