A Comparative Study between Various Elevation Systems, Accuracy Estimation, Determination of Plumb Line Deflection in Northeastern Syria

Abstract

The Syrian leveling network was established in the first half of the nineteenth century by three different parties (French – Russian – Syrian) and it covers approximately 70% of the area of Syria. 

The lack of development and updating of this network since its establishment, its inconsistency in some areas, the damage it has suffered during the years of war, and the loss of its points in many locations constitute a major challenge that hinders the densification of this network, especially at reconstruction project sites in Syria or in utilizing from modern surveying technologies such as the Global Positioning System (GPS). 

In this research, the basic heights used in surveying were reviewed, and the normal heights (H^N) calculated from the Earth's gravity field were proposed as an alternative to orthometric heights computed by spirit leveling and referenced to mean sea level. A digital elevation model was constructed from the available points in the study area to derive the normal height at any point, and then this study was generalized to a large part of Syria where gravity measurements (g) or gravity anomaly maps are available. Finally, the deflection of the vertical was determined in the study area and its effect on the horizontal positioning of points was assessed.