There are several reasons a vessel may appear more than once in the search results.
– If a vessel is present in both AIS and VMS datasets, we will show one result per activity layer the vessel is present in. When you select a vessel, the layer it is from will be displayed in the toolbox.
– A vessel may change some of its identifiers and as a result, our algorithm recognizes this as multiple vessels.
– AIS data is noisy and some vessels ‘spoof’ identities, making it difficult to uniquely identify vessels. For example, more than one vessel may transmit the same identifier at the same time (MMSI, ship name, callsign, IMO). Our algorithms try to solve this by splitting these vessels using location, speed and other calculations, resulting in multiple vessels with the same identifier.