Yes, AIS can show the wrong ship position because connected sensor data may be inaccurate even when equipment integrity tests report no failure. This discrepancy arises from two primary sources: internal sensor errors and external target inaccuracies.
The built-in integrity test on an Automatic Identification System (AIS) unit checks for hardware malfunctions but does not validate the accuracy of the connected sensor data feeding it. Consequently, routine checks and corroboration remain necessary to ensure the data is reliable, as the system cannot distinguish between a functional sensor providing bad data and a fully operational unit.
Furthermore, AIS target position and motion are supplied directly by the target's own equipment, whereas radar provides measurements relative to the observer's ship. These two sources may therefore disagree significantly, requiring cross-checking to identify potential errors. It is also important to note that not all ships carry AIS, fitted units may be switched off in limited safety or security circumstances, and received data may be incomplete, unavailable or wrong.
