Module 19 - Electronic Navigation
Electronic Navigation Mindset
What you will learn
Classify what each display is actually showing, distinguish repeated data from independent evidence and choose a safe response when the navigation picture conflicts.
Electronic navigation is a system of sensors, data, software, displays, power and human decisions. A precise screen is useful evidence only when the navigator understands its source, limits and relationship to the physical world.
Electronic navigation is an aid to navigation, not a separate standard of seamanship. A Yachtmaster-level navigator asks which sensor, chart, route, heading source, power supply and network sit behind each displayed value before treating several agreeing screens as corroboration.
Cross-checking means comparing evidence with meaningfully different failure paths. A correctly identified radar range, visual transit, compass heading, log trend or depth contour can challenge a GNSS-derived picture, but each observation still has identification, timing, datum and instrument limits. When important evidence conflicts, protect the vessel first: reduce exposure, create sea room and move to the briefed fallback before troubleshooting the display.
For most leisure craft, the RYA currently identifies paper charts as the viable official chart source because there is not yet an approved digital system suitable for most small craft. A plotter or app may remain extremely useful, but its chart status, coverage, update process and display behaviour must be understood rather than inferred from appearance.
| Display or observation | Likely dependency | What it can establish |
|---|---|---|
| Plotter, tablet and DSC position | Shared GNSS, route or network | One repeated electronic position path |
| Radar range to an identified headland | Radar set-up, target identity and charted feature | A range line with a different failure path |
| Depth trend | Sounder offset, tide, seabed and chart datum | A challenge to clearance or position, not an exact fix |
| Visual transit | Correct feature identity and visibility | One line of position or directional cue |
Challenge an agreeing screen picture
During a night approach, the plotter, tablet and DSC radio show the same GNSS position while a radar range and the depth trend place the yacht closer to danger.
1. Trace the source
Identify the position sensor, chart database, route file, heading input, power and network behind each display.
2. Classify the check
Separate repeated GNSS data from observations with different failure paths, then verify feature identity, time and instrument set-up.
3. Protect the vessel
Disengage suspect route following, reduce exposure and use the pre-briefed sea-room, holding or diversion option.
4. Rebuild the picture
Advance from the last accepted position using checked compass, log, radar, visual and depth evidence until position integrity is coherent again.
Sense check: Three displays using one GNSS solution are one position path, not three independent fixes.
Common mistake or limitation
- Agreement between screens does not prove independence when they share the same sensor, chart or route.
- A paper plot of a GNSS position repeats the GNSS source; it does not independently verify that position.
- A depth or radar discrepancy can challenge the display without identifying one exact position by itself.
- Troubleshooting equipment before protecting sea room can spend the margin needed for a safe fallback.
Recap
- Trace data, power and network dependencies before counting evidence sources.
- Use observations with different failure modes and state their own limitations.
- Protect sea room and a fallback before diagnosing conflicting electronics.
- For most leisure craft, do not mistake a useful digital chart for an approved official replacement for paper charts.
Optional quick check
Section 1 of 18
The plotter, tablet and DSC radio all repeat one GNSS position while a checked radar range disagrees. How many independent own-ship position paths are shown by the three electronic displays?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
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.