Question 25C6

LRIT (Long-Range Identification and Tracking) requires a satellite system capable of transmitting position data *from* a vessel *to* a shore-based receiving station. GPS (Global Positioning System) is a *receive-only* navigation system. It provides precise location information *to* a receiver on a ship by listening to signals from satellites. However, a standard GPS receiver cannot transmit data back to the satellites or a control center. Therefore, while GPS provides the necessary position coordinates, it does not provide the communication link for LRIT. In contrast, Inmarsat-C, Iridium, and Inmarsat-D+ are all satellite communication systems designed for two-way data transmission (or capable of sending data bursts from the user). They can effectively collect position data (often obtained from an onboard GPS receiver) and transmit it as part of an LRIT report.