An Analytical Study about Evaluation the Accuracy of Topographic Maps and Digital Elevation Models from Stereo Satellite Images

Abstract

Abstract Topographic maps (TMs) play an essential role in spatial data collection. In remote and complex terrains, the importance of the data collected from topographic maps in various applications has led to the search for new techniques and accurate software to enhance mapping accuracy and efficiency. The accuracy of topographic maps and digital elevation models (DEMs) have been evaluated according to available techniques and modern instruments that served the success of this study, such as using the real-time kinematic technique (RTK), which combines with differential ground positioning system (DGPS), using remote sensing technique, by focusing on Leica photogrammetry suit (LPS) software to generate and analysis the results. This study addressed two case studies in the Makhoul Hills to Salah Din Governorate in northeast Iraq because it’s one of the most critical regions characterized by rugged terrain, and it is challenging to reach and get data from field surveying. Many factors highlight the significance of this study. The first factor used Pleiades stereo satellite images with very high resolution (VHR), with spatial resolution reaching (0.5m) for panchromatic images and (2 m) for multispectral images. The second is that overlapping between the adjacent images equals 90 %, in addition to all data available. Taking into account the Archive topographic maps that were published in 1957 by “Royal Dutch Airlines Koninklijke Luchtvaart Maatschappij” (KLM) were used as reference data when needed to compare the elevations of the surface extracted from DEM by using stereo images, the datum of KLM maps was universal transverse Mercator (UTM). the contour lines which were drawn from KLM maps with contour interval (CI) equal to (3m) and map scale 1:25,000 while photo scale 1:30,000, C. I represented the distance between the lines and indicated the accuracy of the maps on a large scale. As much as possible, the reasons behind collecting all data from multiple sources are as follows: To achieve the aim of this study and evaluate the topographic maps from stereo satellite images, (2). extracting high-accuracy DEMs from stereo satellite images, (3). assessing the accuracy of topographic maps and DEMs using ground control points (GCPs) collected in the field by the DGPS (4). the challenge of evaluating the accuracy of high-quality maps for hard-to-reach regions. Finally, A statistical analysis was performed to measure the differences in terrain elevations between rugged and flat areas to evaluate the accuracy of DEMs and TMs. This study concluded the differences were (0.992m) in flat regions and (1.482 m) in rugged areas, according to the computed values for the root mean square error (RMSE). Also, rugged and flat regions have standard deviations (STD) of (1.643 and 1.071) m, respectively. The results were within the allowable RMSE values of (1 m) for plain surfaces and (5 m) for rough terrain. That was extracted from stereo satellite images when running the LPS software. These results proved the work’s reliability and the maps’ accuracy. It is possible to verify the accuracy of the data by increasing the number of checkpoints for the study area so that they are used as GCPS to ensure the results and are not operated inside the block file while using the LPS program.