Evaluation of the Accuracy of Open-Source DEMs using GPS Data (original) (raw)

External Validation of the ASTER GDEM2, GMTED2010 and CGIAR-CSI- SRTM v4.1 Free Access Digital Elevation Models (DEMs) in Tunisia and Algeria

Remote Sensing, 2014

Digital Elevation Models (DEMs) including Advanced Spaceborne Thermal Emission and Reflection Radiometer-Global Digital Elevation Model (ASTER GDEM), Shuttle Radar Topography Mission (SRTM), and Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010) are freely available for nearly the entire earth's surface. DEMs that are usually subject to errors need to be evaluated using reference elevation data of higher accuracy. This work was performed to assess the vertical accuracy of the ASTER GDEM version 2, (ASTER GDEM2), the Consultative Group on International Agriculture Research-Consortium for Spatial Information (CGIAR-CSI) SRTM version 4.1 (SRTM v4.1) and the systematic subsample GMTED2010, at their original spatial resolution, using Global Navigation Satellite Systems (GNSS) validation points. Two test sites, the Anaguid Saharan platform in southern Tunisia and the Tebessa basin in north eastern Algeria, were chosen for accuracy assessment of the above mentioned DEMs, based on geostatistical and statistical measurements. Within the geostatistical approach, empirical variograms of each DEM were compared with those of the GPS validation points. Statistical measures were computed from the elevation differences between the DEM pixel value and the corresponding GPS point. For each DEM, a Root Mean Square Error (RMSE) was determined for model validation. In addition, statistical tools such as frequency histograms and Q-Q plots were used to OPEN ACCESS Remote Sens. 2014, 6 4601 evaluate error distributions in each DEM. The results indicate that the vertical accuracy of SRTM model is much higher than ASTER GDEM2 and GMTED2010 for both sites. In Anaguid test site, the vertical accuracy of SRTM is estimated 3.6 m (in terms of RMSE) 5.3 m and 4.5 m for the ASTERGDEM2 and GMTED2010 DEMs, respectively. In Tebessa test site, the overall vertical accuracy shows a RMSE of 9.8 m, 8.3 m and 9.6 m for ASTER GDEM 2, SRTM and GMTED2010 DEM, respectively. This work is the first study to report the lower accuracy of ASTER GDEM2 compared to the GMTED2010 data.

Comparison of Accuracy of Two Global DEMs, and the Extracted DEM from the Topographic Map of the Tafilah Governorate

Journal of Earth Science and Engineering, 2017

SRTM DEM (shuttle radar topographic mission digital elevation model) and ASTEMR DEM (advanced space-borne thermal emission and reflection radiometer digital elevation model) are now freely available in two resolutions: 90 m and 30 m. DEM is a computerized representation of the Earth's relief, and is used in many applications such as hydrology, climatology, geomorphology and ecology. There are some important differences in assessing the accuracy of digital elevation models for specific applications. The purpose of this study is to investigate the errors in digital elevation models obtained globally from DEMs 90 m, 30 m ground resolution, and the extracted DEM from a topographic map by digitized contour lines of 1:50,000 scale in a rugged mountainous region and a heterogeneous landscape, using KS (kernel smoothing) interpolation method. For validation purposes, datasets of 250-GCPs (ground control points) distributed over the study area were used to evaluate and compare the accuracy of the two global Dems and the DEM extracted from TM. The main results showed that the 30 m resolution global (DEM) is the most accurate one among the three. According to the validation results, SRTM with maximum (+) and minimum (-) error elevation is-10_9. M, with mean deviation of KS is-0.00238667, and RMS (root-mean-square) error of 0.98, and currently the most accurate model is 30 m DEM of the study area with no significant differences compared with DEM 90 m.

Accuracy Assessment of Srtm-Dem Using Gps Measurments and Gis Techniques

2010

Shuttle Radar Topographic Mission (SRTM) has created datasets of global elevations that is freely available for modeling and environmental applications. The global availability (almost 80% of the Earth surface) of SRTM data provides baseline information for geospatial applications such as mapping, hydrology, navigation, GIS applications, and reconnaissance. Assessment of the accuracy of SRTM requires regional studies involving points with known elevations at higher level of precision than the SRTM, usually measured with Global Positioning System (GPS). This study based on datasets collected with a differential GPS system in different locations in Iraq. These measurements were corrected with differential methods to reach to sub – centimeter accuracy. Statistical analysis included estimation of absolute errors by Root Mean Square Error (RMSE), Standard Deviation (SD). RMSE was found as (5.15m) for Iraq and the SD was (3.93). This is higher than the standard SRTM-DEM accuracy which is ...

Accuracy Assessment of world DEMs versus Local DEM in Egypt

‫العالمية‬ ‫الرقمية‬ ‫األرتفاعات‬ ‫لنماذج‬ ‫الرأسية‬ ‫الدقة‬ ‫تقييم‬ ‫الي‬ ‫البحث‬ ‫هذا‬ ‫يهدف‬ ASTER ‫و‬ SRTM ‫ومقارنه‬ ‫الدقة‬ ‫تلك‬ ‫الط‬ ‫الخرائط‬ ‫من‬ ‫الناتج‬ ‫المحلي‬ ‫النموذج‬ ‫بدقة‬ ‫رسم‬ ‫مقياس‬ ‫ذات‬ ‫وبغرافية‬ 0001111 , ‫بالتطبيق‬ ‫منطقة‬ ‫علي‬ ‫اختيرت‬ ‫في‬ ‫طول‬ ‫خطي‬ ‫بين‬ ‫النيل‬ ‫وادي‬ ‫من‬ ‫الشمالي‬ ‫الجزء‬ 01 -0010 ‫عرض‬ ‫وخطي‬ 00 -82 ‫بمساحة‬ 01,111 ‫كم‬ 8 ‫حيث‬ ‫نقاط‬ ‫من‬ ‫محموعة‬ ‫فيها‬ ‫توافرت‬ ‫االرضية‬ ‫الثوابت‬ ‫التي‬ ‫استخدمت‬ ‫التقيم‬ ‫عملية‬ ‫في‬ 1 ‫النتائج‬ ‫اظهرت‬ ‫االخطاء‬ ‫لمتوسط‬ ‫التربيعي‬ ‫الجزر‬ ‫بداللة‬ ‫الراسية‬ ‫الدقة‬ ‫ان‬ ( (RMSE ‫لنموذج‬ SRTM ‫افضل‬ ‫دقة‬ ‫لل‬ ‫نماذج‬ ‫ثالث‬ ‫و‬ ‫النموذ‬ ‫دقة‬ ‫عن‬ ‫جدا‬ ‫ضئيل‬ ‫بفارق‬ ‫ج‬ ‫المحلي‬ ‫الطوبغرافية‬ ‫الخرائط‬ ‫من‬ ‫الناتج‬ , ‫ي‬ ‫بينما‬ ‫أ‬ ‫نموذج‬ ‫تي‬ ASTER ‫المرتبة‬ ‫في‬ ‫األ‬ ‫خيرة‬ 1 ‫في‬ ‫تفاوت‬ ‫وجود‬ ‫لوحظ‬ ‫وقد‬ ‫متوسط‬ ‫ال‬ ‫قيم‬ ‫اال‬ ‫في‬ ‫فروق‬ ‫األ‬ ‫الثوابت‬ ‫بين‬ ‫رتفاع‬ ‫رضي‬ ‫النماذج‬ ‫في‬ ‫يقابلها‬ ‫وما‬ ‫ة‬ ‫الثالث‬ , ‫كبير‬ ‫الفارق‬ ‫كان‬ ‫حيث‬ (12.5m) ‫حالة‬ ‫في‬ ASTER ‫حالة‬ ‫في‬ ‫وضئيل‬ SRTM ‫الفارق‬ ‫هذا‬ ‫كان‬ ‫بينما‬ ‫النموذج‬ ‫حالة‬ ‫في‬ ‫محسوس‬ ‫غير‬ ‫المحلي‬ 1 ‫نموذج‬ ‫دقة‬ ‫تحسنت‬ ‫الفروق‬ ‫هذه‬ ‫وبازالة‬ ASTER ‫حيث‬ ‫كبير‬ ‫بشكل‬ ‫وصلت‬ ‫الي‬ ‫التحسن‬ ‫نسبة‬ 0.12 % ‫األ‬ ‫فوق‬ ‫األ‬ ‫متوسطة‬ ‫راضي‬ ‫و‬ ‫نحدار‬ 8212 % ‫األ‬ ‫فوق‬ ‫بينما‬ ‫المستوية‬ ‫راضي‬ ‫كان‬ ‫التحس‬ ‫األ‬ ‫النموذجين‬ ‫حالة‬ ‫في‬ ‫الدقة‬ ‫في‬ ‫ن‬ ‫طفيف‬ ‫خريين‬ ‫األ‬ ‫جدا‬ ‫علي‬ ‫دل‬ ‫الذي‬ ‫مر‬ ‫أ‬ ‫نموذج‬ ‫ن‬ ASTER ‫من‬ ‫يعاني‬ ‫ازاحة‬ ‫وجود‬ ‫رأسية‬ ‫منهجية‬ 1 ‫و‬ ‫حيث‬ ‫أ‬ ‫ان‬ ‫النتائج‬ ‫ظهرت‬ ‫األ‬ ‫لمتوسط‬ ‫التربيعي‬ ‫الجزر‬ ‫خطاء‬ ‫لنموذج‬ SRTM ‫من‬ ‫أقل‬ ‫المستخدمة‬ ‫الكنتورية‬ ‫الفترة‬ ‫نصف‬ ‫الخرائط‬ ‫في‬ ‫مقياس‬ ‫ذات‬ ‫الطوبغرافية‬ ‫رسم‬ 0001,111 ‫النموذج‬ ‫هذا‬ ‫فان‬ ‫يصلح‬ ‫لتحديث‬ ‫مثل‬ ‫هذه‬ ‫الخرائط‬ , ‫نموذج‬ ‫يحتاج‬ ‫بينما‬ ASTER ‫ال‬ ‫تصحيح‬ ‫ي‬ ‫الرأسية‬ ‫ازاحته‬ ‫لتحديت‬ ‫يصلح‬ ‫كي‬ ‫الخرائط‬ ‫ذات‬ ‫الطوبغرافية‬ ‫مقاييس‬ ‫أ‬ ‫رسم‬ ‫قل‬ 1

Evaluation and Validation of Recent Freely-Available ASTER-GDEM V.2, SRTM V.4.1 and the DEM Derived from Topographical Map over SW Grombalia (Test Area) in North East of Tunisia

Journal of Geographic Information System, 2015

Digital Elevation Models (DEMs) provide one of the most useful digital datasets for a wide range of users. Both the Shuttle Radar Topographic Mission (STRM V.4.1) topography and the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER-GDEM V.2) have been widely used in geomorphology, hydrology, tectonic, and others since they were made access to the public. The magnitude of vertical errors of two near-global DEMs-SRTM and ASTER-GDEM is compared and validated against a reference DEM which has a relatively high precision of 1:25,000 scale constructed from topographical map. Moreover, the reference DEM, ASTER-GDEM and SRTM were used as basic topographic data to extract some Morphometric index. The parameters like slope and shaded reflectance maps, were derived from the elevation distribution to provide a more sensitive indication of DEM quality. A square area in the North East of Tunisia was selected as a case study to test and evaluate the elevation accuracy of ASTER-GDEM and SRTM. The relative accuracy approach and absolute accuracy were adopted to evaluate global DEMs. The comparisons show that SRTM overestimates and ASTER-GDEM underestimates elevations, both DEMs can be used to extract the elevations of required geometric data, i.e. sub watershed boundaries, drainage information and cross sections. However, small errors still exist in. The lower root mean square errors values indicate that SRTM is comparatively more accurate than ASTER-GDEM.

Vertical accuracy assessment of Open source Digital Elevation Model (a case study from northern Morocco)

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...

Accuracy Assessment of DEMs Using Modern Geoinformatic Methods

2019

Digital Elevation Models (DEMs), which can come in the form of digital surface models or digital terrain models, are key tools in land analyses and other purposes. Classical methods such as field surveying and photogrammetry can yield high-accuracy terrain data, but they are time consuming and labor-intensive. Nowadays, different modernistic height-finding methods have emerged, including Global Positioning System (GPS) and airborne methods. In contrast to the airborne ways that are suited to gain highly precise, fine-resolution DEMs at a local scale. The airborne ways are complementary to their space-borne matches, such as Light Detection and Ranging (LiDAR), Shuttle Radar Topography Mission (SRTM), Advanced Spaceborne Thermal Emission and Reflection RadiometerGlobal Digital Elevation Model (ASTER GDEM) and Advanced Land Observing Satellite (ALOS). LiDAR data acquisition has become the standard approach for collecting point data to interpolate high-resolution ground and aboveground ...

Evaluation of Vertical Accuracy of Airborne IFSAR and Open Source Digital Elevation Models (DEMs) Based on GPS Observation

International Journal of Computing, Communication and Instrumentation Engineering

A Digital Elevation Model (DEM) is a digital representation of ground surface topography. DEMs are used for various applications including flood modeling. The objective of this paper is to evaluate the vertical accuracy of the DEMs acquired from different sources. The study area covered several districts in Kedah, Malaysia. To determine the accuracies of DEMs acquired from NEXTMap Interferometric Synthetic Aperture Radar (IFSAR), ASTER Global Digital Elevation Model (GDEM) and SRTM Void Fill, height points are compared with the Global Positioning System (GPS) height observations. A total of 100 height points extracted from ASTER GDEM and SRTM is also compared with IFSAR Digital Surface Model (DSM). Four (4) different elevation profiles are generated and the heights are compared. The results obtained have shown that the Root Mean Squares Errors (RMSEs) of IFSAR DTM, IFSAR DSM, ASTER GDEM and SRTM over a relatively flat area are ±0.497 m, ±1.529 m, ±5.848 m and ±4.268 m respectively. Over an undulating area, the accuracies of IFSAR DTM, IFSAR DSM, ASTER GDEM and SRTM are ±0.841 m, ±2.092 m, ±3.278 m and ± 5.300 m respectively. Although there are variations between heights generated from these DEMs in some areas along cross-section, the pattern of height profiles is still quite similar. Future work will concentrate on the techniques of converting DEM acquired from ASTER GDEM and SRTM into DSM and the effects of using different DEMs on the accuracy flood inundation mapping.

Absolute Surface Elevations Accuracies Assessment of Different DEMs Using Ground Truth Data Over Kingdom of Bahrain

For small islands, accurate digital elevation model (DEM) can help to understand the sea level rise prediction and scenarios impact on coastal zones, flooding risks assessment, flood inundation modelling, erosion and landslide, and environmental disaster process management. Currently, DEMs are available from several different sources using space borne systems, photogrammetry, surveying, topographic contour lines, etc. The aim of this study focuses on a comparison of absolute surface heights accuracies of four independent DEMs datasets over small island as Kingdom of Bahrain. The first two DEMs were acquired with space borne, Shuttle Radar Topographic Mission (SRTM-V4.1) and Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER-V2.1) with 30 m pixel size. The second two DEMs with 2.5 m (DEM-2.5) and 5 m (DEM-5) spatial resolutions were derived from two different topographic contour lines maps at scales, respectively, 1:5000 and 1:25000 using inverse distance weighted (IDW) interpolation method. For validation purposes, a datasets of 400 ground control points uniformly distributed over the study site were used. They were measured using a Differential Global Position System (DGPS) assuring ± 1 and ± 2 cm accuracies, respectively, for planimetry and altimetry. The obtained results show that the derived DEM-2.5 exhibit the best accuracy ± 0.55 m which is excellent by reference to the tolerance or maximum error ± 0.78 m calculated based on errors sources propagation. As well, the DEM-5 shows very good accuracy ± 1.37 m by reference to the calculated tolerance ± 1.54 m. Then, SRTM shows a satisfactory performance with ± 3.00 m accuracy which is less than the absolute vertical height accuracy (± 5.6 m) advocated by NASA for African continent and Middle-East regions. Finally, the achieved ASTER accuracy ± 8.40 m is better than the estimated error (± 17.01 m) by USGS and JAXA.

Accuracy Assessment of Aster Global Dem Over Turkey

2010

The aim of this study is to analyze the accuracy of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) over Istanbul metropolitan city. Accuracy assessment was conducted by comparing ASTER GDEM with a reference DEM derived from 1/5.000-scaled topographic maps. The selected area has wide range of elevations since it covers coastal and mountainous areas. Different land cover types like urban, sea, lakes, agricultural land, forest, grasslands, bare lands are available within the study area. The accuracy assessment of GDEM was performed by visual interpretation and statistical analysis. Throughout the statistical analysis, several transects representing different types of land cover and topography were selected and minimum, maximum and mean errors and Root Mean Square Error values of each transect were calculated, respectively. The quality of ASTER GDEM was analyzed for Istanbul region and it was found that ASTER GDEM could repre...