Accuracy of coordinate transformations in GIS and AIS systems - Example of the Adriatic Sea
Tea Duplančić Leder; Nenad Leder (HHI);
4th International Maritime Science Conference, Book of Proceedings / Rosanda Mulić, Zvonko Gržetić, Pero Vidan, Ivica Kuzmanić (ur.). Split, Croatia : Faculty of Maritime Studies Split,, 2012. 174-178 (predavanje,međunarodna recenzija,objavljeni rad,znanstveni).
Modern GPS equipment for geodetic coordinates position fixing is based upon worldwide used satellite positioning methods and it gives position on the global WGS datum. In the Republic of Croatia topographic maps and nautical charts have been produced on the local Helmannskoegel datum and Bessel rotational ellipsoid. The world market offers a large number of software packages which calculate transformations from the local to the global datum, some of them being free and available on the internet. Reference geodetic coordinates shown on different datums may result in a position error of some hundred metres. Mathematical conversion of a geodetic position from one datum to another is called transformation. Among several models of transformation between the two datums, the following ones are usually used: seven-parameter also called Helmert transformation and three-parameter or Molodensky transformation. All available GIS and AIS systems mainly used two programs for coordinate transformation: PCTrans developed by Netherlands Hydrographic Service, and Geotrans - Geographic Translator, developed by the US Army Topographic Centre and National Geospatial Intelligence Agency. In this article we would estimate accuracy and usability of the programs for transformation of geodetic coordinates between local and global datums, used in GIS and AIS systems.