The transformation of coordinates between the global coordinate system yield
ellipsoid WGS84 (World Geodetic System 1984) and the local coordinate system yield
ellipsoid Clark1880 in different regions of Syria, is the essential step in the effectiv
e use of
GNSS (Global Navigation Satellite Systems) surveying techniques in Syria, and the
transformation occurs with 3D transformation between one ellipsoid and another, or 2D
transformation directly between two planar. The transformation must be understood,
analyzed and tested. The research is about the accuracy of the 2D transformation in small
area to give coordinates can be directly used in different surveying and engineering works,
and about studying the common points number and their distribution effect on
transformation accuracy, and conclude that the biggest effect on transformation accuracy is
for the common points distribution.
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.
