الفهرس 
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Abstract
The Western Desert Oases are one of the most promising areas in Egypt. They have a lot of significant natural features that can take part in logistic projects in Egypt, such as the cultivation of million Acres. Until now, there is no precise local geoid model for Egypt due to the lack of data. Recently, great progress has been achieved on the computation of local geoids based on a new satellite mission and recent geoid computation methodology. Besides the geodetic importance of the local geoid computation at the selected region as an important vertical datum, it would shade more light on the lithospheric thickness and the hotspot pattern. Shallow geologic structures significantly influence heat flow patterns on the surface. The local hybrid geoid model for the Western Desert is computed by recent data, including the global geopotential model, gravimetric measurements, and a highly resolute digital topographic model. The research indicates the importance of accurate local geoid computation as a survey datum and figures out the crustal structure. Detailed crustal structure patterns could reveal the origin of artesian aquifers and geothermal activities of the selected region.
In this research, the recent global geopotential model deduced from a recent satellite mission has been used. The selected region is characterized by a rough topographic pattern, making it an interesting target as a local geoid model. Six recent global geopotential models are evaluated as long and medium wavelength. GGM accuracy for each model has been computed using GPS leveling data. EIGEN-6C model with spherical harmonic degree equal to 250 gives the smallest error with a standard deviation 0.019mGal. Also, a high-resolution digital topographic model with 3arcsec is used for terrain correction. The resulted geoid has been evaluated using GPS leveling within the selected region. The study shows that recent GGMs could overcome irregular terrestrial gravity data.
Also, there is always a need to find renewable energy sources such as geothermal energy. Geothermal energy can be exploited if it shows high thermal gradient than around. Heat may flow to the Earth’s surface either by the thinning lithosphere or through the availability of vertical joints to enable the heat activity to flow upward from the mantle to the crust.
Geoid, which is the vertical surveying datum, represents the equipotential surface of the Earth. It figures out deep-seated gravity variation and inconsequence mass distribution. As there is a correlation between the geoid and deep Earth-mass density and on the other hand, there is a correlation between geoid and mantle convection. However, the poor horizontal resolution of the geoid model limited the deep Earth studies. But, there are significant improvements of the global geoid model based on the recent satellite missions. Moreover, the local geoid model, which includes both geopotential model and ground-based gravity observation, increases its resolution, accuracy, and applications.
The Oases region in the Western Desert shows some locations of high thermal gradient activities, some of which rise to the Earth’s surface. In this region, a local geoid model has been computed. In the current research, the resulting local geoid model over the study region is utilized to evaluate the geothermal activity. The study shows the important location of lithosphere topography related to geothermal activities and would be able to figure out the geothermal pattern of the study region.
GOCE gravity tool for geothermal exploration is also used to display the main geothermal activities through the study area. Most hot springs’ locations are related to the thinning in the lithosphere and less related to structures such as fractures or faults in the crustal layer. The 2D modeling of gravity and aeromagnetic data are applied to determine subsurface geology and the basement relief structure and the determination of density and magnetic sustainability of each section.
The 2D modeling technique helps to understand the irregular pattern of the basement of varying depths reflecting uplifted basement reaching up to 482m and down- faulted basins/sub-basins reaching up to more than 6235 m. In general, the basement depth ranges from 25 m to more than 6412 m below the ground surface but the average depth equal to 2 km. Also, some intrusive bodies were recorded along with the modeling profiles at the surface.The geothermal gradient and heat flow, extracted from the CPDs. The geothermal gradient values in Western Desert range from 15 – 59 oC/km with an average value of around 30 oC/km. The results show that the Oases region of Western Desert has ”after the current study” a precise local geoid model and new exploration and evaluation of geothermal activities.