was the first mandate for the use of AIS equipment and affected approximately 100,000 vessels. In 2006, the AIS standards committee published the Class B type AIS transceiver specification, designed to enable a simpler and lower-cost AIS device. Low-cost Class B transceivers became available in the same year triggering mandate adoptions by numerous countries and making large-scale installation of AIS devices on vessels of all sizes commercially viable. Since 2006, the AIS technical standard committees have continued to evolve the AIS standard and product types to cover a wide range of applications from the largest vessel to small fishing vessels and life boats. In parallel, governments and authorities have instigated projects to fit varying classes of vessels with an AIS device to improve safety and security. Most mandates are focused on commercial vessels, with leisure vessels selectively choosing to fit. In 2010 most commercial vessels operating on the European Inland Waterways were required to fit an Inland waterway certified Class A, all EU fishing boats over 15m must have a Class A by May 2014, and the US has a long-pending extension to their existing AIS fit rules which is expected to come into force during 2013. It is estimated that as of 2012, some 250,000 vessels have fitted an AIS transceiver of some type, with a further 1 million required to do so in the near future and even larger projects under consideration. 1 Terrestrial-based AIS (T-AIS) AIS was developed in the 1990s as a high intensity, short-range identification and tracking network. Shipboard and land-based AIS transceivers have a horizontal range that is highly variable, but typically only up to about . Approximate line-of-sight propagation limitations mean that terrestrial AIS (T-AIS) is lost beyond coastal waters. In addition to port and maritime authority operated transceivers, there is large network of privately owned ones as well. Satellite-based AIS (S-AIS) In the 1990s AIS was not anticipated to be detectable from space. Nevertheless, since 2005, various entities have been experimenting with detecting AIS transmissions using satellite-based receivers and, since 2008, companies such as exactEarth, ORBCOMM, Spacequest, Spire and also government programs have deployed AIS receivers on satellites. The time-division multiple access (TDMA) radio access scheme used by the AIS system creates significant technical issues for the reliable reception of AIS messages from all types of transceivers: Class A, Class B, Identifier, AtoN and SART. However, the industry is seeking to address