Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Accuracy Assessment


Accuracy Assessment of Digital Elevation Models Produced From Different Geomatics Data

Imzahim Abdulkareem; Zina Walid Samuel; Qassim K. Abdullah

Engineering and Technology Journal, 2020, Volume 38, Issue 11, Pages 1580-1592
DOI: 10.30684/etj.v38i11A.1318

Digital Elevation Models (DEM) are now being used in several geospatial applications. DEMs play an important role in the preliminary surveys for constructing dams and reservoirs, highways, canals, and projects in which earth work is essential. In many remote sensing applications, DEMs have become a significant tool for InSAR (Interferometric Synthetic Aperture Radar) processing, ground cover classification and images ortho-rectification. In this study, the accuracy of DEMs obtained from ALOS V1.1, ASTER V2, SRTM V3 and other obtained from a pair of Pleiades high-resolution (PHR) 1B satellites in a study area were evaluated after comparing them with high accuracy GNSS/RTK checkpoints. The SRTM3, ALOS V1.1, ASTER V2 DEM revealed a Root Mean Square Error (RMSE) of 2.234m, 0.838m, and 15.116m respectively; while the DEM which is produced from a 0.5m resolution of Pleiades 0.5m shows an RMSE of 0.642m. The correct bias Linear transformation algorithm was used and the RMSE results were: SRTM V3 (1.319m), ALOS V1.1 (0.830m), ASTER V2 (3.815m), and PHR (0.433m). The results showed that the ALOS V1.1 model is the most accurate of the open source models followed by the SRTM V3 model and then followed by ASTER V2. The results obtained from a pair by Pleiades high-resolution (PHR) 1B satellites show a higher accuracy than the results obtained from the open source models.

Accuracy Assessment of World View-2 Satellite Imagery for Planimetric Maps Production

A.Z. Khalaf; I.A.K. Alwan; T.A. Kadhum

Engineering and Technology Journal, 2018, Volume 36, Issue 1A, Pages 1-9
DOI: 10.30684/etj.36.1A.1

A planimetric map of scale 1:10,000 meets the requirements of a large segment of user’s maps for instance urban city planners and various GIS implementations. Nowadays, a very high-resolution satellite images, such as World View02 (WV02) with spatial resolution of 0.5 m, are very important to produce planimetric maps or update existing ones. Main aim of this research is the assessment of WV02 image for production of the planimetric photomap of scale 1:10,000 with class 1 according to ASPRS standards (ASPRS give accuracy tolerances for map scales at 1:20,000 or larger, this accuracy reported as Class 1, 2, or 3). The investigation includes, studying the best-fit mathematical model (order of polynomial transformation model) that can be used to perform geometric correction for the used image. As well as, examine the effect of the ground control points (GCPs) configuration on the accuracy that can reached from photomap by using the best polynomial order. The Root Mean Square Error (RMSE) resulting at the checkpoints (CPs) will be evaluated. Before the study of impact of the mentioned effects, will be studying the possibility of obtaining a photomap with scale of 1:10,000 and determining the class of this map by using raster satellite image directly (raw image). Through it will compare the coordinates of GCPs observed by using Differential Global Positioning System (DGPS) on the raster WV02 satellite image with respect to its true position on the ground. Taking into consideration this comparison will be conducted according to international standards (National Standard for Spatial Data Accuracy (NSSDA) and American Society for Photogrammetry and Remote Sensing (ASPRS) standards). Evidenced by the results that have been accessible, it cannot obtained on photomap with scale of 1:10,000 of class1 according to ASPRS standard from raw WV02 satellite image, because the RMSE was 4.709 m, this value is largest of allowable error value for this class of the scale. Further, the extracted results showed that using a 1st order polynomial for WV02 image correction with the 14 GCPs that well distributed is slightly superior to other order polynomials (2nd and 3rd order) with a total RMSE of 0.790 m at the 8 ground CPs. On the other hand, using 13 GCPs well distributed (covers the wholly raster of the used image) for the correction process with the same polynomial order, the total RMSE obtained is 0.894 m obtained at 9 CPs, which is less than the value of two pixel size (user-threshold value) of WV02 image. As well as, according to NSSDA and ASPRS standards, this result satisfies the requirements of large-scale maps production accuracy (larger than 1:10,000). In addition, by decreasing the number of the GCPs (using 9 GCPs until 4) the reliability of the results decreases (i.e., the horizontal error increased, approximately 1.4 m are obtained at CPs), but at the same time can get a photomap within scale of 1:10,000.

Accuracy Assessment of Lidar Data Using Geomatic Approaches

Abbas Z. Khalfa; Imzahim Abdul Kareem Alwan; Adnan R. Mechman

Engineering and Technology Journal, 2013, Volume 31, Issue 4, Pages 692-702

The fast development in Remote Sensing technology with various sources of data especially LiDAR (Light Detection And Ranging) images promote the ability of using data , but the accuracy of produce Maps issue always need to be evaluate.
So the main aim of this research is to evaluate the accuracy of using elevation data for various techniques, such as Photogrammetry and remote sensing techniques then comparison with traditional filed surveying using DGPS total station and level instrument.
LiDAR data gives accurate elevation therefore; 3D model can be obtained from LiDAR data which can be used in many applications such as civil engineering and surveying engineering, etc.
In this research University of Technology has been chosen as case study area, and many Geomatic approaches executed such as extracted height of features from field surveys using Total Station and comparison with the heights extracted from LiDAR data. According to the results analysis it can be stated that the elevations from the LiDAR data within accuracy of (3-10) cm can be obtained