Transformation of Geodetic Coordinates Between Datums Used in Syria by Multiple Regressing Equations

Abstract

The geodetic network does not cover the entire area of Syria. This network has been damaged in different areas over years; whether in vacant or damaged places, some of its points have become unreliable and inaccurate.  Syria has been utilizing Global Navigation Satellite Systems (GNSS) technology for geodetic applications. In order to apply the GNSS acquired data locally, it is necessary to transform coordinates from the global datum WGS84 to the Syrian local geodetic datum Clarke-1880, but the aforementioned damage to the geodetic network has led to an absence of common transformation parameters in Syria to carry out the transformation from the global to the local reference datums; this further complicates and impedes the use of GNSS measurements and thus necessitates the search for an      appropriate method of transformation between the two reference datums used in Syria. In this study, the Multiple Regression Equations technique was applied in 2 dimensions to a sample of points, whose geodetic coordinates are known on the global and local datums, distributed almost equally over the area of Syria. Transformation parameters were calculated using polynomials of the fifth degree by means of the least squares method; these parameters allow for calculating the differences of the geodetic coordinates between the global and local references for any point in Syria.  The geodetic coordinates of the points on Clarke-1880 were calculated by adding those differences to the geodetic coordinates measured by the global positioning system (GPS) and then calculating the Cartesian coordinates in the Syrian Stereographic system. The resulting linear Positioning Accuracy of the points is about ±3.81m