Method for vertical accuracy assessment of digital elevation models derived from remote sensing data (original) (raw)
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Article, 2020
Introduction: A digital elevation model (DEM) allows for the analysis of specific features on the earth's surface in three dimensions. The engineering DEM is useful to evaluate resources and design management strategies. Objective: To evaluate the technical-operational feasibility of generating DEMs from total station (TS) topographic surveys, GPS RTK and aerial photogrammetry using an unmanned aerial vehicle (UAV). Methodology: A 20x20 m grid was traced in a plot without vegetation (1.4 ha) located in Montecillo, Estado de México, and topographic surveys were carried out with three methods, from which DEMs were generated for graphic and statistical evaluation and by tracing contour lines. Results: The estimated statistical errors were 0.15, 0.15 and 0.02 m, for TS vs. UAV, GPS RTK vs. UAV and TS vs. GPS RTK, respectively. Study limitations: The instruments used and the geographical conditions of central Mexico may be a reason for variation when extrapolating the results with other devices. Originality: A methodology is provided to generate DEMs accurately. The results allow the user to make reasoned choices based on the equipment available. Conclusion: The DEMs generated with TS and GPS RTK data have a smaller error than the one obtained from UAVs. The use of UAV helps in the representation of the terrain, since it generates a dense cloud of points that strengthens the procedure for topographic surveys. Resumen Introducción: Un modelo digital de elevación (MDE) permite analizar rasgos específicos sobre la superficie terrestre en tres dimensiones. El MDE en ingeniería es útil para evaluar recursos y diseñar estrategias de manejo. Objetivo: Evaluar la viabilidad técnica-operativa de generar MDE a partir de levantamientos topográficos con estación total (ET), GPS RTK y fotogrametría aérea usando un vehículo aéreo no tripulado (VANT). Metodología: Se trazó una cuadrícula de 20 x 20 m en una parcela sin vegetación (1.4 ha) ubicada en Montecillo, Edo. de México, y se realizaron levantamientos topográficos con tres métodos, a partir de los cuales se generaron los MDE para su evaluación gráfica, estadística y mediante el trazo de curvas de nivel. Resultados: Los errores estadísticos estimados fueron de 0.15, 0.15 y 0.02 m, para ET vs. VANT, GPS RTK vs. VANT y ET vs. GPS RTK, respectivamente. Limitaciones del estudio: El instrumental usado y las condiciones geográficas del centro de México pueden ser motivo de variación al momento de extrapolar los resultados con otros dispositivos. Originalidad: Se proporciona una metodología para generar MDE con precisión. Los resultados permiten al usuario tomar decisiones razonadas en función del equipo con el que dispone. Conclusión: Los MDE generados con datos de ET y GPS RTK tienen un error menor que el obtenido a partir de VANT. El uso del VANT ayuda en la representación del terreno, ya que genera una densa nube de puntos que fortalece el procedimiento para levantamientos topográficos.
ISPRS International Journal of Geo-Information
Digital elevation models (DEMs) provide important support to research since these data are freely available for almost all areas of the terrestrial surface. Thus, it is important to assess their accuracy for correct applicability regarding the correct use scale. Therefore, this paper aims to assess the vertical accuracy of ALOS PALSAR, GMTED2010, SRTM, and Topodata DEMs according to the Brazilian Cartographic Accuracy Standard through the official high accuracy network data of the Brazilian Geodetic System. This study also seeks to investigate whether the altimetric error is correlated with altitude and slope in the study area. Our results showed that the four assessed DEMs in this study demonstrated satisfactory accuracy to provide mappings in scales up to 1:100,000 because more than 90% of the extracted points presented altimetric errors of less than 25 m when compared with the reference points from the high accuracy network of the Brazilian Geodetic System. Regarding the altimetr...
International Journal of Innovation and Applied Studies, 2016
Digital elevation models (DEMs), as its name suggests, is a digital representation of ground in terms of altitude. It provides information not only on landforms but also on their geolocation; this is why it is considered one of the most useful digital data sets for a wide range of users. Various field, remote, and laboratory techniques can generate DEMs. Some of the DEMs such as ASTER, SRTM, and GTOPO30 are freely available open source products; however, the accuracy of these data sets is often unknown and is uneven within each dataset due to radar characteristics, type of topography, and physical properties of the surface. In this study, we evaluate open source DEMs (ASTER and SRTM) and their derived attributes using a reference DEM produced by contours maps interpolation and ground control points. In fact, the quality of derived attributes of DEMs such as slopes and drainage network is closely linked to accuracy of DEMs. While Open source DEMs partially show low accuracy in high e...
Digital elevation model (DEM) is a digital representation of ground surface topography and have been used in various applications. The introduction of global coverage DEM available for free or at reasonable cost was a new phenomenon in mapping. The issue is how accurate are these datasets and can it be used for topographic mapping. This paper aims to evaluate the height accuracy of DEMs generated from different sources. Results presented in this paper is part of a study to evaluate the suitable use of different DEMs and high resolution imagery for topographic map updating. For this paper, Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM), Intermap Airborne Interferometric Synthetic Aperture Radar Digital Terrain Model (IFSAR DTM), IFSAR Digital Surface Model (IFSAR DSM), digital topographic map (with a 5m contour interval) and Light Detection and Ranging (LiDAR) datasets are used to generate the contours, height points and height profiles. LiDAR dataset is used as reference DEM to evaluate the accuracy of NEXTMap IFSAR DTM and Digital Terrain Model (DTM) generated from digital topographic maps acquired from the Department of Survey and Mapping Malaysia. The vertical accuracy of ASTER GDEM is obtained by comparing wih the heights of IFSAR DSM. The Root Mean Squares Error (RMSE) of the height points generated from IFSAR DTM and digital topographic map of the non-vegetated areas within the study area are 1.458 m and 2.960 m respectively. For the vegetated area, the RMSE of IFSAR DTM and digital topographic map are 4.736 m and 9.848 m respectively. The accuracy of ASTER GDEM in the vegetated and non-vegetated areas are 8.442 m and 18.900 m respectively. Visual comparison between the contours generated from IFSAR DTM and LiDAR has shown promising result. ASTER GDEM can be used to capture the general characteristic of the terrain. Future work will include the evaluation of factors that contribute to the accuracy of DEMs generated from different sources.
Evaluation of vertical accuracy of open source Digital Elevation Model (DEM)
International Journal of …
Digital Elevation Model (DEM) is a quantitative representation of terrain and is important for Earth science and hydrological applications. DEM can be generated using photogrammetry, interferometry, ground and laser surveying and other techniques. Some of the DEMs such as ASTER, SRTM, and GTOPO 30 are freely available open source products. Each DEM contains intrinsic errors due to primary data acquisition technology and processing methodology in relation with a particular terrain and land cover type. The accuracy of these datasets is often unknown and is non-uniform within each dataset. In this study we evaluate open source DEMs (ASTER and SRTM) and their derived attributes using high postings Cartosat DEM and Survey of India (SOI) height information. It was found that representation of terrain characteristics is affected in the coarse postings DEM. The overall vertical accuracy shows RMS error of 12.62 m and 17.76 m for ASTER and SRTM DEM respectively, when compared with Cartosat DEM. The slope and drainage network delineation are also violated. The terrain morphology strongly influences the DEM accuracy. These results can be highly useful for researchers using such products in various modeling exercises.
Vertical Accuracy Assessment of ALOS PALSAR, GMTED2010, SRTM and Topodata Digital Elevation Models
2021
Three-dimensional data of the Earth's surface can support several types of studies, such as hydrological, geomorphological, environmental monitoring, among many others. But, due to the difficulty of acquiring these data in the field, freely available Digital Elevation Models (DEM) have been widely used, and therefore, it is increasingly necessary to check their accuracy to ensure their correct applicability according to the appropriate scale. However, there are no studies which have assessed specifically the vertical accuracy of the ALOS PALSAR, GMTED2010, SRTM and Topodata DEMs according to Brazilian Cartographic Accuracy Standard (PEC). In this sense, this paper aims to evaluate the quality of the above-mentioned DEMs by using the official high accuracy altimetric network data of the Brazilian Geodetic System. Statistical analysis of errors results demonstrated that the DEMs have applications compatible with 1:100,000 scales or smaller than this, and although the GMTED2010 pre...
ACCURACY ASSESSMENT OF DIGITAL ELEVATION MODELS OBTAINED FROM DIFFERENT DATA AND METHODS
ACCURACY ASSESSMENT OF DIGITAL ELEVATION MODELS OBTAINED FROM DIFFERENT DATA AND METHODS, 2017
Digital elevation model (DEM) is primarily a way of visualising 2D maps, photographs and images in 3D. Common uses of DEMs are creation of relief maps, rendering of 3D visualizations, rectification of satellites images and aerial photographs, creation of different physical models, etc. DEMs can be produced by different methods. In this study, DEMs are produced by 1:25000 digital topographic maps, Light Detection and Ranging (LIDAR) data, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Shuttle Radar Topographic Mission (SRTM) data, and the accuracy of these models are analysed.
2014
ABSTARCT Ground surveying methods are main sources for digital elevation data that is usually utilized in the creation of a Digital Elevation Model (DEM). DEM usually is a main input in many Engineering and Environmental applications. The quality of the DEM is a vital issue that controls the qualities of outputs in different applications. Different factors including the data source, the data density, the sampling method, the spatial resolution and the interpolation scheme control the quality of the DEM. This research is focused towards investigating the effects of the spatial resolution of the DEMs generated from ground surveying data on their qualities where digital elevation data has been collected from a test area of corrugated terrain using ground surveying methods. Qualitative and quantitative analyses have been applied on DEMs created from digital elevation data with different resolutions through; visual analysis, statistical analysis, profile analysis and finally accuracy ass...
Accuracy assessment of digital elevation models using a non-parametric approach
This paper explores three theoretical approaches for estimating the degree of correctness to which the accuracy figures of a gridded Digital Elevation Model (DEM) have been estimated depending on the number of checkpoints involved in the assessment process. The widely used average-error statistic Mean Square Error (MSE) was selected for measuring the DEM accuracy. The work was focused on DEM uncertainty assessment using approximate confidence intervals. Those confidence intervals were constructed both from classical methods which assume a normal distribution of the error and from a new method based on a non-parametric approach. The first two approaches studied, called Chi-squared and Asymptotic Student t, consider a normal distribution of the residuals. That is especially true in the first case. The second case, due to the asymptotic properties of the t distribution, can perform reasonably well with even slightly non-normal residuals if the sample size is large enough. The third approach developed in this article is a new method based on the theory of estimating functions which could be considered much more general than the previous two cases. It is based on a non-parametric approach where no particular distribution is assumed. Thus, we can avoid the strong assumption of distribution normality accepted in previous work and in the majority of current standards of positional accuracy. The three approaches were tested using Monte Carlo simulation for several populations of residuals generated from originally sampled data. Those original grid DEMs, considered as ground data, were collected by means of digital photogrammetric methods from seven areas displaying differing morphology employing a 2 by 2 m sampling interval. The original grid DEMs were subsampled to generate new lower-resolution DEMs. Each of these new DEMs was then interpolated to retrieve its original resolution using two different procedures. Height differences between original and interpolated grid DEMs were calculated to obtain residual populations. One interpolation procedure resulted in slightly non-normal residual populations, whereas the other produced very non-normal residuals with frequent outliers. Monte Carlo simulations allow us to report that the estimating function approach was the most robust and general of those tested. In fact, the other two approaches, especially the Chi-squared method, were clearly affected by the degree of normality of the residual population distribution, producing less reliable results than the estimating functions approach. This last method shows good results when applied to the different datasets, even in the case of more leptokurtic populations. In the worst cases, no more than 64-128 checkpoints were required to construct an estimate of the global error of the DEM with 95% confidence. The approach therefore is an important step towards saving time and money in the evaluation of DEM accuracy using a single average-error statistic. Nevertheless, we must take into account that MSE is essentially a single global measure of deviations, and thus incapable of characterizing the spatial variations of errors over the interpolated surface.
Generation and Accuracy Assessment of Digital Elevation Models in Mountain Area
2015
Nowadays DEMs are indispensable tools in studies and analysis regarding Earth’s surface. Generating DEMs closely to the true surfaces and with high accuracy represent a main issue. The aim of the study is to improve the geomorphometric analysis based on DEMs. In this study a statistical approach was used to assess various DEMs generated with different methods to compare their accuracy. DEMs were created on the base of a topographic map using classical interpolation methods (Spline, IDW, Kriging, Simple linear interpolation) and simulated surfaces. The results suggest that data source is more important in error propagation, followed by interpolation methods.