Module 19 - Electronic Navigation
Yachtmaster Offshore Standard: Electronics
What you will learn
Convert conflicting electronic and physical evidence into a concise command decision that preserves sea room, assigns crew roles and defines what would reopen the route.
The RYA Yachtmaster Offshore practical exam assesses navigation, skippering and safety aboard. This lesson can rehearse evidence control and command language, but it cannot demonstrate practical radar use, equipment fluency or command competence.
A Yachtmaster answer should begin with the vessel, not the screen. State the last position and time the team accepts, identify which data paths now conflict, and explain the immediate action that protects sea room. Do not spend the remaining margin proving that an attractive display is right.
Separate observations, estimates and repeated data. GNSS position and SOG, AIS overlay, DSC position and route-following autopilot can all share one receiver. A radar range, transit or depth trend can offer a different failure path, but only after its own identity, timing, datum and instrument context are checked.
Name the threshold that closes the route: a position discrepancy, cross-track limit, depth trend, time gate, visibility limit, target track or loss of a critical sensor. Then state the conservative option and the evidence required before the original route or automation can be restored.
Brief roles in short, observable terms. One person controls heading and speed, one maintains lookout and radar observations, and one rebuilds position and clearance from the last accepted evidence. The exact allocation depends on vessel and crew; the principle is to prevent one overloaded navigator from troubleshooting, steering and assessing traffic at the same time.
Worked example
At 2310 the main plotter and tablet agree because they share one GNSS receiver and copied route. A verified radar range supports a position 0.4 M towards the shoal, while checked depth is 0.8 m less than the route plan expected.
- 1Count the plotter and tablet as one position path because GNSS and route data are shared.
- 2Treat the radar result as different evidence after confirming range scale, feature identity, timing and charted geometry.
- 3Treat the 0.8 m depth discrepancy as a material challenge after checking transducer offset, tide, squat, seabed and datum; do not convert it into one exact horizontal position.
- 4Keep the shoal-side route closed, reduce exposure and use the briefed sea-room or holding option while position and clearance are rebuilt.
- 5Restore the route only after checked evidence with different failure paths forms a coherent picture and the remaining margin still supports it.
Sense check: Averaging the displayed and radar-supported positions would create a tidy midpoint without resolving which dependency failed or how much clearance remains.
| Evidence | Classification | Command consequence |
|---|---|---|
| Plotter and tablet agree | One shared GNSS/route path | Do not count as independent corroboration |
| Verified radar range | Observation with different failure modes | Use with identity, timing and geometry checks |
| Depth 0.8 m less than expected | Material clearance challenge | Protect the shoal-side case; check offsets and tide |
| Sea-room or holding option open | Controllable fallback | Use it before troubleshooting consumes the margin |
Issue the first command after a common-source conflict
The plotter, tablet and autopilot follow one GNSS route during a night approach. A verified radar range and the depth trend place the yacht closer to a shoal than the displayed track.
1. Break dependence
Disengage route following and use a briefed safe heading, speed and sea-room option.
2. State the evidence
Name the last accepted fix, shared GNSS path, checked radar observation and depth discrepancy.
3. Assign roles
Separate helm, lookout/radar and navigation reconstruction so each critical task remains monitored.
4. Define reopening
Require coherent position and clearance evidence with different failure modes before restoring the route.
Sense check: The crew should be able to repeat the safe heading or area, the suspect source and the next evidence trigger without interpreting a technical lecture.
Common mistake or limitation
- Several agreeing screens are not independent when they share position, chart or route data.
- A depth discrepancy can challenge the plan without proving one exact position or cause.
- Troubleshooting before breaking route-following dependence can continue steering the yacht towards the error.
- A restored signal or rebooted display does not by itself re-establish position integrity.
Recap
- Begin with the last accepted evidence and the action that protects the vessel.
- Classify shared data, independent observations and estimates explicitly.
- Assign helm, lookout/radar and navigation reconstruction roles.
- Reopen a route only when coherent evidence and margin support it.
Optional quick check
Section 17 of 18
Three route-following displays share GNSS and route data while verified radar and depth evidence disagree. What is the strongest first command?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
- RYA Yachtmaster Offshore examination scope
- RYA Coastal Skipper/Yachtmaster Offshore Theory course
- RYA Digital First: the rise of eNavigation
- MCA MGN 610 Amendment 1 — navigation and voyage planning
- MCA MGN 379 Amendment 1 — electronic navigational aids
- MCA MGN 324 Amendment 2 — VHF radio and AIS
- IMO Resolution A.1106(29) — operational use and limits of AIS
- IMO Convention on the International Regulations for Preventing Collisions at Sea
Continue studying Electronic Navigation
This public lesson is part of Revision Module 19. Full revision access adds the guided Learn, Practise and Test flow, flashcards and revision progress.