Paper Title
Application of Total Free Station Method (TFS) for Offshore Surveying in Oblique Coordinate System

The article presents accuracy study of the Total Free Station (TFS) method applied to determine the sensors’offsets based on the measurements taken from the unstable platform which is frequently the case in offshore surveying. In the research the measurements were made in the oblique reference system with the application of Total Station. The survey was carried out on board Navigator XXI vessel in unstable conditions (the ship was in flating conditions at the quayside ). Then accuracy analyses were carried out based on the network of the reference points installed and measured on the vessel. Next, i t was researched which of the calculation methods produce the most accurate results. In particular, the TFS transformation method with the center of gravity assumed as the system origin was studied. The results of the surveys indicate achievable accuracy of measurements when the vessel is moving, e.g. to determine the sensors’ offsets from the origin of the vessel coordinate frame. TFS technology can also be used to dimension an object in its own coordinate system, including unstable conditions when the object is in motion. Index Terms - Oblique coordinate system, offshore surveying, similarity transformations, Total Free Station – TFS.