Review on National Geodetic Control Network - Sri Lankan Datum 1999 (SLD_99)

Abstract

Any country in the world has its own geodetic coordinate system and it is very useful in all types of surveying activities. Accuracy of the geodetic control network is very important in every aspect. In Sri Lanka (Early named as Ceylon), the systematic triangulation process began in 1857 and completed in 1885. This network was recomputed with some additional observation done in 1890 due to inconsistencies occurring mainly in the minor triangulation. But later found that, the new introduced fixing values have serious error. A new horizontal control network was established in 1999 with using Global Positioning System (GPS) and there were included thirty two (32) old network points to calculate the transformation parameters between the old local datum (Kandawala Datum) and the new horizontal network. But new system and old system gives different coordinates for same control points. In this study, Kandawala network is compared with new SLD_99 network to find differences between these two networks. Scaled out figure of the ten secondary control points of SLD_99 were observed with GPS observations and analyzed to perform a network adjustment and for comparison.