Assessments of recent Global Geopotential Models based on GPS/levelling and gravity data along coastal zones of Egypt

Abstract

The orthometric height has an essential role in a variety of civil engineering projects and it is defined as the length of the curved plumbline from a point (on the earth surface) to its intersection with the geoid surface. Leveling process is considered as the most accurate technique for obtaining these heights. However, regardless of its potentials, it is tedious, costly, and time consuming. Recently many organizations and research centers have developed multi Global Geopotential Models (GGMs) depending on several types of available gravity and height datasets to estimate orthometric heights from GNSS measurements. In this study, we present an evaluation and assessment of the accuracy of five of recent and popular GGMS: XGM2016, XGM2019e, EIGEN-6C4, GO_CONS_GCF_2_TIM_R6e, and EGM2008 using actual 145 GNSS/leveling points and 96 terrestrial gravity points. The goal of this research is to find the best fit model along the study area located along the coastal zones of Egypt with distances of about 1,970 km for further determination of geoid modeling at regional scale. The selection of these areas basically was due to their developmental, urban, and economical importance and their continuous need for protection works to fight against the coastal erosion caused by climate change and global warming. The results indicated that for geoid undulation, GO_CONS_GCF_2_TIM_R6e model is the best fit GGM for the estimation of geoid model along Mediterranean Sea coastal line, while XGM2019e_2159 model is the best suitable for coastal line of the Red Sea. And regarding the gravity anomalies, the most reliable GGMs for this study area are XGM2019e_2159 and EIGEN-6C4 for Bouguer and free-air gravity anomaly, respectively.

Methodology of Applying Inverse Distance Weighting Interpolation Method in Determining Normal Heights

“…The chosen sites were located in Bekaa, Mount Lebanon, and North governorates and named Site B, site M, and Site N respectively. This method aimed to determine both ellipsoidal and normal heights, while also investigating the height anomaly in the areas (Al Shouny et al, 2023). Through this research, efforts are being made to improve the understanding and measurement of normal heights in Lebanon.…”

Assessment of some global geopotential models over Egypt and the Kingdom of Saudi Arabia

“…The first study area is in Egypt, and 17 GPS/Levelling HARN points are used. The ellipsoidal heights of these points are known on the WGS84, and the orthometric heights of them are also known as first-order levelling related to the mean sea level, see Figure (2). The second study area comprises 86 points distributed over KSA by a 1° X 1° grid.…”

“…The HARN consists of 30 stations approximately 200 km apart, covering all of Egypt with a standard accuracy of 1:10,000,000 [11]. Figure (2) shows the positions of these points.…”

Evaluating the Impact of the Recent Combined and Satellite-Only Global Geopotential Model on the Gravimetric Geoid Model

“…The determination of a precise gravimetric geoid model is of utmost importance in geodesy and geophysics. Geoid serves as a fundamental benchmark in determining elevations in relation to mean sea level and holds significance in a range of practical contexts, including surveying, mapping, navigation, and geophysical studies [1]. It provides a consistent reference surface for surveying and mapping, enabling elevation measurement, vertical datum establishment, and standardisation of height measurements across different locations.…”