A system for assisting docking of a vessel, comprising: - at least one sensor arranged on the vessel to provide measurement data of distinct points from a dock location and its surrounding area; - a data processing unit connected to the at least one sensor for processing a first set of distinct points at the dock location and a second set of distinct points at the surrounding area, the first and second set of distinct points (140, 150) being represented by their 3D coordinates relative to the position of the sensor; - a registration unit connected to the data processing unit registering at least one first point in the first set of distinct points and at least one second point in the second set of distinct points; - a first tracking unit connected to the registration unit tracking the registered at least one first point in the first set of distinct points; - a second tracking unit connected to the registration unit tracking the registered at least one second point in the second set of distinct points, characterized in that - the first and second tracking units (210, 220) are connected to each other and the data processing unit, and when the registered and tracked at least one first point in the first set at distinct points of the dock location no longer can be tracked in a final phase of the docking, the registered and tracked at least one first point in the first set of distinct points is updated in the data processing unit, represented by 3D coordinates relative to the registered and tracked at least one second point in the second set of distinct points; - a distance calculating unit is connected to the first and second tracking units (210,220) which calculates the distance between the vessel and the dock location by using updates of 3D coordinates of both sets of distinct points (140, 150) obtained from the first and second tracking units (210, 220). - at least one sensor arranged on the vessel to provide measurement data of distinct points from a dock location and its surrounding area; - a data processing unit connected to the at least one sensor for processing a first set of distinct points at the dock location and a second set of distinct points at the surrounding area, the first and second set of distinct points (140, 150) being represented by their 3D coordinates relative to the position of the sensor; - a registration unit connected to the data processing unit registering at least one first point in the first set of distinct points and at least one second point in the second set of distinct points; - a first tracking unit connected to the registration unit tracking the registered at least one first point in the first set of distinct points; - a second tracking unit connected to the registration unit tracking the registered at least one second point in the second set of distinct points, - the first and second tracking units (210, 220) are connected to each other and the data processing unit, and when the registered and tracked at least one first point in the first set at distinct points of the dock location no longer can be tracked in a final phase of the docking, the registered and tracked at least one first point in the first set of distinct points is updated in the data processing unit, represented by 3D coordinates relative to the registered and tracked at least one second point in the second set of distinct points; - a distance calculating unit is connected to the first and second tracking units (210,220) which calculates the distance between the vessel and the dock location by using updates of 3D coordinates of both sets of distinct points (140, 150) obtained from the first and second tracking units (210, 220).