This chart tracks SV TENACIOUS.
Our ship has an AIS transponder on board, which transmits its position, speed and course, among some other information, such as it’s name, dimensions and voyage details.
Whilst the AIS transmits on a frequent basis, the position of the ship can only be shown if within range of an AIS receiving station (usually 15-20 nautical miles), though this can be much further depending on the elevation of the receiving base station.
In addition, they transmit the position regularly via a satellite system for when out of range of land.
AIS