Describe AIS — what information it transmits, what the OOW uses it for, and what its limitations are for collision avoidance.

A. AIS — AUTOMATIC IDENTIFICATION SYSTEM: WHAT IT BROADCASTS (Class A — required for SOLAS vessels 300 GT+): (1) DYNAMIC DATA (automatically updated from GPS and sensors): MMSI, position (lat/lon), time (UTC), COG (course over ground), SOG (speed over ground), heading (from gyro/compass), rate of turn, navigational status (underway using engine, at anchor, etc.); (2) STATIC DATA (entered by operator, updated at least every 6 minutes): vessel name, call sign, MMSI, IMO number, type of ship, length and beam, position of GPS antenna; (3) VOYAGE-RELATED DATA (updated by operator): draught, destination, ETA, type of cargo, number of persons on board. OOW USES: (1) TRAFFIC MANAGEMENT: identify vessels by name/type/destination — valuable in complex traffic; (2) COLLISION RISK: obtain course/speed of another vessel to supplement radar — CPA/TCPA calculation; (3) DISTRESS: AIS receivers alert when a vessel transmits AIS in distress mode; (4) VHF COMMUNICATION: identify the vessel to call on Ch 16/Ch 16 by name; LIMITATIONS: (1) NOT ALL VESSELS FIT AIS: vessels under 300 GT, fishing vessels under 15m, recreational craft — do NOT carry AIS. You cannot assume every vessel shows on AIS; (2) AIS DATA CAN BE WRONG: operators entering incorrect voyage data; MMSI conflicts; GPS errors; some vessels transmit wrong navigational status; (3) AIS IS NOT A COLLISION AVOIDANCE SYSTEM: COLREG radar rules apply — do not substitute AIS for radar observation; (4) INTERFERENCE: AIS can be overwhelmed in busy ports where hundreds of vessels transmit simultaneously.

B. AIS transmits only vessel name and MMSI. Course, speed, and position are not transmitted on AIS — these require radar measurement.

C. AIS is a collision avoidance system that supersedes COLREG Rules in vessels fitted with Class A transceivers. When AIS shows a safe CPA, COLREG avoiding action is not required.

D. AIS is mandatory for all vessels over 15 metres in international waters. Vessels under 15m are not required to fit AIS and are therefore not visible to ships.

A. DSC DISTRESS ALERT — VHF PROCEDURE: DSC (Digital Selective Calling) on VHF Channel 70 is the primary GMDSS distress alerting mechanism. PROCEDURE: (1) ENSURE POSITION IS UPDATED: the DSC controller must have a current GPS position input (most modern sets auto-update from GPS). Verify the position shown is current; (2) OPEN THE DSC CONTROLLER: navigate to the distress function — typically a protected button (lift cover or press and hold to prevent accidental activation); (3) SELECT NATURE OF DISTRESS: most DSC controllers allow selection of distress nature — UNDESIGNATED, FIRE, FLOODING, COLLISION, GROUNDING, LISTING, SINKING, DISABLED AND ADRIFT, ABANDONING SHIP. If time permits, select the correct nature; (4) TRANSMIT: press/hold the distress button for the required duration (typically 5 seconds with button confirmation). The controller transmits the DSC distress call on Ch 70 — this broadcasts your MMSI, position, time, nature of distress to all vessels in range and to coast stations; (5) SWITCH TO CH 16: immediately after DSC transmission, switch VHF to Ch 16 and transmit the voice MAYDAY message; (6) MAYDAY VOICE: "MAYDAY MAYDAY MAYDAY — THIS IS [vessel name × 3] — MAYDAY [vessel name] — POSITION [lat/lon] — [NATURE OF DISTRESS] — [POB] — [ANY OTHER RELEVANT INFO] — OVER"; (7) AWAIT ACKNOWLEDGEMENT: coast stations and vessels will acknowledge on Ch 16.

B. The DSC distress alert is transmitted on Ch 16. Tune the VHF to Ch 16, press the distress button, and speak the MAYDAY message directly.

C. Voice MAYDAY on Ch 16 must be transmitted first — then the DSC alert follows. The voice call alerts nearby vessels who may not be monitoring DSC.

D. DSC distress is only for MF/HF radio. VHF uses the traditional voice MAYDAY on Ch 16 only — VHF DSC is not a required GMDSS function.

A. NAVTEX — SYSTEM AND OOW USE: NAVTEX (Navigational Telex) is an automated system that broadcasts maritime safety information (MSI) on 518 kHz (international) and 490 kHz (national language) using NBDP (Narrow Band Direct Printing). WHAT IT PROVIDES: (1) NAVIGATIONAL WARNINGS (B messages): hazards to navigation — wrecks, buoy off station, new obstructions, pilot areas, lights changed; (2) METEOROLOGICAL WARNINGS (W messages): gale warnings, storm warnings, weather bulletins; (3) PILOT SERVICE MESSAGES (P messages); (4) ICE REPORTS (I messages); (5) SAR INFORMATION (D messages): distress messages, SAR operations in the area; (6) SUBFACTS and NAVFACTS: submarine exercise areas and other military notifications. HOW IT WORKS: NAVTEX stations broadcast on a schedule. Each station has a unique letter identifier. The NAVTEX receiver is programmed to receive messages from stations covering your sea area. Messages not relevant to the vessel's area can be filtered. OOW DUTIES: (1) Ensure NAVTEX is switched on and printing; (2) Check the NAVTEX receiver is set to receive messages from stations in the current sea area; (3) READ ALL MESSAGES as they print; (4) Bring significant messages (navigational warnings, gale warnings, SAR in the area) to the master's attention; (5) CHART PLOT: plot navigational warnings on the chart/ECDIS; (6) Do NOT ignore NAVTEX messages — they contain safety-critical information.

B. NAVTEX operates on VHF Ch 68 and provides local port information for vessels within 20nm of the coast. It is only relevant when approaching port.

C. NAVTEX is a backup to weather fax and provides only meteorological information. Navigational warnings are only available through the vessel's AIS.

D. NAVTEX messages should be collected and reviewed once per watch. Urgent messages are highlighted in red and require immediate action; all others can wait.