Estimating Coordinates Transformation Parameters from Global to Local Coordinates Systems in Lebanese Republic Based on Zonal Division

The widespread use of Global Navigation Satellite Systems (GNSS) in geodesy necessitates the transformation of coordinates from global to national systems, a process that can introduce spatial errors. This research focuses on evaluating the accuracy of coordinate transformations to the national coordinate system of Lebanon, which uses the double stereographic projection on the CLARKE 1880 ellipsoid. Specifically, the study examines the horizontal plane accuracy of this transformation process. The Lebanese map was divided into five zones for this study. Transformation parameters were generated for each zone by combining International Terrestrial Reference Frame (ITRF) 2014 coordinates (obtained using an online precise point positioning service) with CLARKE 1880 coordinates calculated from known geodetic coordinates. The newly calculated parameters were then tested against the adopted parameters using 39 check points, and positional errors in the horizontal plane were analyzed. Additionally, the inverse distance weight method was employed to interpolate transformation parameters at the boundaries between zones. The applied method significantly reduced positional errors in projected coordinates at most check points. Furthermore, the successful application of the inverse distance weight method for interpolation proved effective in minimizing positional discrepancies when transforming coordinates in areas located along zone boundaries.