DESCRIZIONE
Method for determining the accuracy of information received as a part of an AIS (Automatic Identification System) message.
The invention is characterised in that at least three receivers (320,330,340), respective clocks of which have been previously synchronized, receive one and the same radio signal (520) from a certain sender (310), in that each of the receivers determine the time of receipt of the same predetermined signal element of the received signal, in that a location of the sender is determined by triangulation, based upon the respective location of the three receivers in combination with differences in the respective point in time for the respective receipt of the said signal element, in that the hence determined location for the sender (310), and/or a heading and/or a velocity which has been calculated based upon several consecutive calculations of the location of the sender (310), is compared to a location and/or a heading and/or a velocity for the sender (310) which is stated in an AIS message which is sent out from the sender (310), in that a warning signal is emitted in case the two positions and/or headings and/or velocities are pairwise different by more than a respective predetermined value, and in that the respective time of receipt of said time of receipt is determined, by each respective one of said receivers (320,330,340), by determining a stream of data bits from a digitally stored sampled signal representing the said radio signal, by correlating said sampled signal to a digital comparison signal constructed to simulate the said sampled signal and on the basis of said stream of data bits. [Image Omitted]