Within the last thirty years, the recent development in GPS, satellite tracking techniques and processing strategies has revolutionized development of Earth gravity field models. In addition, the increase of gravity data coverage led to an increase i
n the resolution and accuracy of these models. This in turn led to a noticeable improvement in determination of geoid surfaces which are essential in transformation of the geodetic height to the orthometric height. This study utilizes the normal gravity field for estimating offsets the Syrian leveling network from the EGM2008 geoid defined by its geopotential value W0=62636856.0 m2s-2. This approach uses the average of the gravity potential values at the GPS/levelling points in some areas in Syria. The gravity potential value in the study regionis estimated using the Earth gravity field model EGM2008. The residuals between the actual gravity potentials and the values at the Syrian height reference surface are estimated in the range between [-4.51 m2s-2 ~ 10.62m2s-2] and a mean value of -6.72±0.70 m2s-2 with 95% confidence level. This corresponds to [-46.0 cm ~ 108.4 cm] and a mean value of -63.7±7.1 cm which means that the Syrian height datum is located underneath the global geoid.
The Earth's gravity field is related to the Earth's mass and shape and to the
position, where we apply the measurement.The measured value in any place
depends on the altitude of the place angle and Earth's rotation speed around
itself.
In the pap
er we present a theoretical idea connecting the value of gravity with
the above mentioned amounts. Next we calculated the value of this field in
some Syrian cities.
The paper is ended by important note, that the obtained relations allowing to
calculate the value of the gravity field depends on the place altitude, not on the
one's Longitude.
