Towards an Accurate Definition of the Local Geoid Model in Egypt using GPS/Leveling Data: A Case Study at Rosetta Zone
Essam M. Al-Krargy1, Mohamed I. Doma2, Gomaa M. Dawod3
1Eng. Essam Mohamed Farag ALkrargy, Asst. Researcher of Survey Research Institute, Department of Physical Geodesy, National Water Research Center, Cairo, Egypt.
2Dr. Mohamed Ismail Ali Doma, Assoc. Prof. of Surveying and Geodesy, Department of Civil Engineering, Faculty of Engineering, Menoufia University, Egypt.
3Prof. Gomaa Mohamed Dawod, Department of Physical Geodesy, Survey Research Institute, National Water Research Center, Cairo, Egypt.
Manuscript received on October 01, 2014. | Revised Manuscript received on October 05, 2014. | Manuscript published on October 15, 2014. | PP: 10-15 | Volume-2 Issue-11, October 2014. | Retrieval Number: K07251021114/2014©BEIESP
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Abstract: Nowadays the Global Positioning System (GPS) is one of the most favorite techniques in practical geodesy. A major dilemma in GPS surveying lies in its ellipsoidal-based type of heights, while in engineering practice orthometric heights are usually utilized. Thus, it is important to convert GPS heights into orthometric heights through applying an accurate geoid model. The objectives of this paper are to model a local geoid in the study area using GPS/levelling technique, and to evaluate the performance of several Global Geopotential Models (GGMs) particularly the OUS-91A, EGM96 and EGM2008 in the study area, which is located in the northern Egypt at Rosetta zone area. The accomplished results show that the EGM 2008 represents the most precise global geopotential model to be used for geoid determination in Egypt. Furthermore, the achievable accuracy of local geoid determination in the study area after using regression method models is ranges between 0.059 meter to -0.083 meter, with an average -0.01 meter and standard deviation of ± 0.05 meter. It is concluded that increasing the number of control points with well spatial distribution will result in developing a precise geoid model for Egypt.
Keywords: Global Geopotential Models (GGMs), Global Positioning System (GPS), Local geoid. Orthometric height.