Transformation parameters between ITRS, WGS84 and ETRS89
Horizontal positions at sea are often expressed in longitudes and latitudes. They are based on coordinate reference systems, also known as geodetic datums. In Europe, the most important geodetic datums for such coordinates are WGS84, ETRS89 and ITRS. These coordinate reference systems have different levels of accuracy. Sometimes coordinates need to be recalculated (transformed) to express a position in a different geodetic datum.