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Abstract
A NEW GRAVIMETRIC GEOID MODEL FOR THE UNITED ARAB EMIRATES
Adel Khaleefa Alshams
Dr. Geodesy
Military Survey Departement (MSD),
Email: alshamsi@uaesurvey.ae
The first precise gravimetric geoid for the United Arab Emirates (UAE) has been computed using FFT technique. In carrying out the task, substantial gravity data for the entire country has been gathered through land gravity measurement and compilation of the existing marine and land gravity anomalies. A total of nine (9) new absolute gravity stations were established throughout the UAE forming gravity base network to provide control for the detail gravity survey. The land gravity surveys are conducted on a nominal 5 x 5 km grid. The free-air gravity anomalies have been deduced accurate to ±0.2 mGal. Marine gravity data used in this study is the combination of GECO and Mobil ship-borne gravity data. Comparison with altimetry derived marine gravity anomalies shows RMS differences of ±5mGal. Residual terrain correction model (RTM) has been used in the geoid computation. Geopotential geoid derived from EGM96 and PGM2000A models agree with geometric derived geoid heights at ±0.38m level of accuracy. The GRAVSOFT package is used in computing the 1-D and 2-D FFT gravimetric geoids for the UAE (21º N ≤ φ ≤27ºN and 50ºE ≤ λ ≤58ºE). Generally the geoid is having minimum and maximum values of –34m and –24m, respectively. The higher geoid is observed in the north-eastern part with the steep slope of about 10m over the distance of less than 50km over the mountainous areas. Elsewhere the geoid is very gentle over the fairly flat region of the UAE. The new geoid heights that have been computed at selected benchmarks showing agreement with the corresponding geometric geoid heights at ±5cm level of accuracy.
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