Reliability in positioning of a vessel

The article describes the question of relative and precise positioning. The analysis of various systems of positioning from a robustness point of view is given. It is noted in the work that in the coastal areas of navigation the determination of the location of the vessel by a visual method or using a radar based on objects on the map or distinct landmarks of the coastline gives a fairly reliable absolute position of the vessel. The image of the radar echoes overlaid on the ECDIS map makes this clear and detailed. Finally, he comes to the conclusion that there is a need to improve existing systems as well as the creation of new and reliable positioning systems