Ace the ECDIS Exam 2025 – Navigate Your Path to Success!

The presence of more AIS Class A units in close proximity to a ship can lead to a shorter effective range of AIS target detection due to the phenomenon known as 'AIS congestion.' When many vessels transmit their AIS signals simultaneously, especially in busy waterways, the signals can interfere with one another. This congestion can result in reduced clarity and reliability of the received data, making it more challenging for a ship's AIS receiver to detect and decode signals from nearby vessels effectively.

In heavy traffic situations, the overload of transmissions can cause delays, missed messages, or loss of information about other nearby ships. This means that while you might expect the effective range of detection to increase with more AIS units present, the reality is that the opposite can occur due to this interference, ultimately resulting in a compromised situational awareness for navigators relying on those AIS signals.

Other choices, such as having no effect or longer effective range, do not take into account the challenges posed by signal interference in congested marine environments. Additionally, interference with GPS signals is not directly related to the proximity of AIS units but rather other factors such as physical obstructions or electronic interference from devices not related to AIS operation.