Accuracy Analysis of Dems Derived from Aster Imagery (original) (raw)
Related papers
Performance evaluation of global and absolute DEMs generated from ASTER stereo imagery
2011
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) digital stereo image could be used to generate Digital Elevation Model (DEM), which represents the terrain elevation in discrete three dimensional (3D) forms. In this research, the performance of the absolute and Global DEMs generated from ASTER stereo image is evaluated for the area of Universiti Teknologi Malaysia (UTM). In doing so, 25 Ground Control Points (GCPs) collected by Global Positioning System (GPS) instrument are used to extract an absolute ASTER DEM. Furthermore, the ASTER Global DEM (GDEM) is acquired for the study area. The accuracy of the DEMs is assessed by comparing them with 20 high accuracy points which were collected using GPS technology. Some statistical parameters such as the Mean Error (ME), Standard Deviation (SD) and Root Mean Square Error (RMSE) are determined for this purpose. The achieved results indicated that the estimated vertical accuracy of the ASTER GDEM is less than 5 m at 80% confidence for the study area while the vertical accuracy of less than 15 m is obtained for the ASTER absolute DEM, which is less than the pixel size of ASTER image. Finally, according to the achieved results, 15 m resolution of ASTER image and the selected number of check points, it can be concluded that the accuracy of DEMs is acceptable for the study area, and could be used for various geoinformation applications.
ACCURACY OF DEM GENERATION FROM TERRA-ASTER STEREO DATA
In this work we studied the accuracy of DEMs generated from ASTER stereoscopic images by automated stereo-matching techniques with two different softwares (OrthoBase PRO and OrthoEngine). We compare several DEMs generated for a test area of 23 km x 28 km situated in the province of Granada (south Spain). This is an area was selected because its variable and complex topography with elevations ranging from 300m up to 2800 m.
Aster Digital Elevation Model and orthorectified images generated on the GEO Grid
2010 IEEE International Geoscience and Remote Sensing Symposium, 2010
(AIST) developed an on-demand processing service on the GEO Grid system [1] to generate a Digital Elevation Model and orthorectified images from an ASTER data [2]. It is designed to support the latest algorithms for radiometric and atmospheric corrections developed by researchers as well as the geometric correction and other DEM processing options. The functions and options in this service are developed and implemented as modules, so that they can be arranged as the user requires. Although the system is an experimental, it can provide higher quality data sets than the standard products. In this paper, we present an overview of ASTER DEM and orthoimage data set (ASTER Data BETA).
Geometric Evaluation, Automated DEM and Orthoimage Generation from Along-Track Stereo ASTER Images
A cloud-free ASTER scene combination covering 61.5km x 63km Zonguldak testfield in the north-west Turkey has been analysed. It comprises the nadir and backward views with a base-to-height ratio of 0.6. The pixel size on the ground is 15m. The bundle orientation was executed with the related module of PCI Geomatica V9.1.4 software package and resulted the 3D geo-positioning to an accuracy of about 14m in planimetry and 13m in height. This level of accuracy can be provided using the number of GCPs up to 14 which are distributed over the scene uniformly. Based on the scene orientation, a DEM of the area has been determined by an automatic image matching and PCI system yielded a DEM with 30m cell size. For the validation of extracted DEM, different groups of GCPs selected over the testfield were utilized. In this analysis, GCPs were located in the raster DEM in according to their planimetric coordinates, then the heights are estimated by the bilinear interpolation of the neighboured grid cells. This was done by the program DEMINT and mean square differences was obtained in the range of 12 to 14m. Moreover, matched DEM was checked against reference DEM based on digitised contour lines from the 1:25000 scale topographic maps using program DEMANAL. The discrepancies between the two DEMs were determined as reference DEM minus matched DEM. Then positive biases resulted which show that matched DEM occurred under the reference DEM. These biases appeared also in the superimposition of contours from two DEMs. Image of DZ discrepancies is dispayed as a function of grey values as well and highest residuals occurred mainly at the ridges. In the meantime, RMSE-Z from the comparison of both DEMs obtained very close in the range of ±21-22m. Finally, orthoimage was generated using matched DEM and nadir image component of ASTER stereopair without problem. Planimetric accuracy check of this product was realized using the GCPs and shows no systematic error pattern overall.
Accuracy Assessment of Digital Elevation Model (DEM) Data Obtained from ASTER Satellite in Flat Land
IOP Conference Series: Materials Science and Engineering
It is important to investigate the accuracy of Digital Elevation Models (DEMs) because of their crucial impact on all engineering and scientific disciplines. Photogrammetry, traditional surveying, remote sensing systems and satellite whole DEMs output methods. In this paper include the DEM data produced by the ASTER satellite (Band near-infrared wavelength region from 0.78 to 0.86 μm), where tested and evaluation DEM data for an area of 100 square kilometers in Al-Shtra city. The technique used to evaluate was twofold: first method was to use statistical methods; second method is to take advantage of applied linear transformation equation to detect the gap between Z-DEM and Z-Global Navigation Satellite System (GNSS) (which represents reality (. The result of a root means square error (RMSE) is 5.087m, where it was calculated based on the observed data in the field using GNSS. And standard deviation error (SDT err) was 5.088 m, while after applied linear transformation equation the RMSE reduction to about 80%, which indicates a large bias between the Z-DEM and Z-GPS.
Performance Estimation of Aster Global DEM Depending upon the Terrain Inclination
Journal of Indian Society of Remote Sensing, 2012
A digital elevation model (DEM) is a source of immense three dimensional data revealing topograph-ic characteristics of any region. The performance of a DEM can be described by accuracy and the morpholog-ic conformity. Both depend upon the quality of data set, the used production technique and the roughness of the terrain. The global DEM of ASTER (Advanced Space-borne Thermal Emission and Reflection Radiometer) was released to public utilization as free of charge on June 2009. It covers virtually overall the globe using 1 arc-second posting interval. Especially easy availability renders ASTER Global DEM (GDEM) one of the most popular and considerable global topographic data for scientific applications. From this point of view, the performance of ASTER GDEM has to be estimated for different kinds of topographies. Accordingly, six test fields from Spain (Barcelona) and Turkey (Istanbul and Zonguldak) have been preferred depending upon the terrain inclination. Thus, the advantages and disadvantages of the DEM product have been proved by means of a group of advanced performance analysis. The analyses indicate that the performance of ASTER GDEM is quite satisfying at urban areas because of flat topography. On the other hand, terrain slope has negative effect on the results. Especially steep, mountainous, forestry topographic formations and the regions which have sudden changes at the altitude have lower accuracy.
This paper describes the methodology of a DEM generation from stereo aerial images and the results of experiments in terms of accuracy of generated DEM. In this study, Images, which have 1/10000 and 1/16000 scale, and a test area established about 1 km 2 in Selcuk University Campus Area were used. Aerial photographs were scanned by ZEISS SCAI Photogrammetric Scanner (pixel size is 21µ). Aerial images, which have 1/10000 scale, were restitutied by Zeiss Planicomp P3 Analytical Instrument. The DEM, which belong to test area, were produced by progressive, selective and composite sampling methods. We have developed a new software on PC's that can automatically generate DEM from stereo aerial images for restitution of images 1/16000 scale. In this software, pixel and image coordinates of points in left and right image are calculated by using colinearity equations. Left and right windows are matched and this process is repeated in various ±∆Z range. Elevation values obtained from the best-fixed matching are automatically selected as optimum elevation value. Elevation values of points in the test area are calculated by bilinear interpolation method which uses coordinates of above points (X,Y,Z). Moreover, Elevations of points in test area are manually produced from PHOTOMOD software. RMS obtained from both analytical and digital methods are compared with similar study in the relevant literature.
2008
Satellite data has become a commonly used information source. Landscapes components such as water, inorganic substances, vegetation, and the atmosphere may be distinguished making use of their spectral characteristics. The above mentioned components may be further divided. For example, inorganic substances may be subdivided into soil, minerals, build up areas etc. The spectral characteristics of soils are determined by moisture, humus contents, mineral composition, surface structure, and the stage of eroding processes. The development in remote sensing tends either to the data acquisition in more spectral bands or the improvement of the resolution of remote sensing data. The terra satellite ranks among new generation satellites; its orbital parameters are similar to the parameters of the Landsat system. ASTER (Advanced Spaceborn Thermal Emission and Reflection Radiometer) is one of the onboard instruments on Terra satellite and captures data in 14 spectral bands. The VNIR (Visible Near Infrared) subsystem provides 15 m spatial resolution data. Two of the VNIR subsystem telescopes enable stereoscopic data evaluation. A stereo-pair consists of 3N (nadir) and 3B (backward) images. A couple of 3N and 3B images can be used for the creation of a digital surface model (DSM) and orthophoto. This article describes the creation of DSM and orthophoto of an area located in the northwest part of the Czech Republic. Images of the area were made in years 2002 and 2005. In this work, level 1B images were used, i.e. images with radiometric and geometric corrections already applied. The model was created through the use of 21 control points selected in each scene. The standard error of coordinates of the control points is up to 15 m, the elevation standard error is approx. 30 m. The accuracy of the final DSM and orthophoto was tested on a set of 13 check points. The position standard error in DSM and orthophoto is approx. 15 m, i.e. just about the size of one pixel of the original data. The elevation standard error of the checkpoints is up to 40 m. The output can be used as a basis for small-scale maps. Using one scene acquired by ASTER instruments, a DSM and orthophoto covering an area of 60 × 60 km can be created.
The along-track stereo images of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor with 15 m resolution were used to generate Digital Elevation Model (DEM) on an area with low and near Mean Sea Level (MSL) elevation in Johor, Malaysia. The absolute DEM was generated by using the Rational Polynomial Coefficient (RPC) model which was run on ENVI 4.8 software. In order to generate the absolute DEM, 60 Ground Control Pointes (GCPs) with almost vertical accuracy less than 10 meter extracted from topographic map of the study area. The assessment was carried out on uncorrected and corrected DEM by utilizing dozens of Independent Check Points (ICPs). Consequently, the uncorrected DEM showed the RMSEz of ± 26.43 meter which was decreased to the RMSEz of ± 16.49 meter for the corrected DEM after post-processing. Overall, the corrected DEM of ASTER stereo images met the expectations.
An Assessment of Digital Elevation Models (DEMs) From Different Spatial Data Sources
Digital Elevation Model (DEM) represents a very important geospatial data type in the analysis and modelling of different hydrological and ecological phenomenon which are required in preserving our immediate environment. DEMs are typically used to represent terrain relief. DEMs are particularly relevant for many applications such as lake and water volumes estimation, soil erosion volumes calculations, flood estimate, quantification of earth materials to be moved for channels, roads, dams, embankment etc.