Module 19 - Electronic Navigation
Chart Plotter Route Checking
What you will learn
Audit every route leg, turn and cross-track corridor at useful scales and close a route that depends on hidden, stale or unverified data.
An electronic route is user-entered geometry over chart data. It becomes usable only after its source, coverage, update status, scale behaviour, dangers, turns and fallback have been checked.
Audit the whole route at an appropriate larger scale that reveals the available source detail, then compare the display scale with the chart data's compilation or source scale. Zooming in beyond the source does not create new accuracy; zooming out may suppress soundings, isolated dangers, text and layers.
Inspect the corridor between waypoints, not only the points. Check every leg, turn direction, wheel-over or arrival behaviour, cross-track limit, overhead and underwater danger, traffic route, tide, weather exposure and position uncertainty. Avoid placing a waypoint on a buoy, headland or danger where route following could drive the yacht towards the object it should clear.
Imported and previously used routes are unverified until their datum, chart coverage, revision, every leg and safe-water margin have been checked for this passage. A route that was safe on another vessel, tide, chart edition or display profile may not be safe now.
Run a leg-by-leg route audit
A copied route appears clear on an overview, but one turn crosses a drying bank when examined at a useful harbour scale.
1. Verify source
Confirm chart coverage, status, datum, route revision and the display profile in use.
2. Inspect geometry
Check every leg, turn and cross-track corridor at a scale that exposes the available detail.
3. Check the passage
Apply current tide, clearance, weather, traffic and vessel manoeuvring limits.
4. Set a fallback
Name the point at which the route closes and the hold, diversion or manual pilotage plan begins.
Sense check: If the route cannot be explained without saying ‘the line looks clear’, the audit is not complete.
Common mistake or limitation
- Zooming in beyond the chart source scale magnifies the display without adding source accuracy.
- Checking only waypoints can miss a danger on the leg or an unsafe turn between them.
- An imported route is not validated by a successful import or by having been used before.
- A cross-track alarm is a monitoring barrier, not permission to use the whole corridor near danger.
Recap
- Verify chart, route and configuration before checking geometry.
- Inspect every leg, turn and corridor at useful scales without over-scaling the source.
- Keep waypoints and route-following geometry in safe water.
- Close the route when its source, margin or fallback is no longer defensible.
Optional quick check
Section 3 of 18
Why is zooming in until a hazard appears sharply separated from the route not enough to prove safe clearance?
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.