Module 12 - Visual Aids to Navigation
Light Sectors
Many lights show different colours in different directions (sectors). These sectors are designed to guide vessels on safe tracks. A white sector might indicate the safe approach channel, while red and green sectors mark the limits or warn of dangers on either side.
Sector boundaries are shown on the chart as dashed lines radiating from the light. The colours are given as abbreviations: W (white), R (red), G (green). When you see the light change colour, you know you have crossed a sector boundary.
Worked example · plan view
The same light can show three colours
Each boat sees the colour shining into its part of the water.
Red
Left of the plan
White
On the planned track
Green
Right of the plan
How to use the colour
- 1Find your boat relative to the light and its charted sector boundaries.
- 2Match the colour you see to the sector containing your boat.
- 3If it changes, check position, depths and your planned correction before steering.
Example only: sector bearings and the safe route come from the chart, not from a universal red-left/green-right rule.
- White sector often = safe channel
- Red/Green sectors often = warning of danger or channel limits
- Sector boundaries shown as dashed lines on chart
- Colour change = you have crossed a sector boundary
Practice pilotage with visual aids
Sector lights make more sense when combined with leading lines, clearing bearings, buoyage, and safe-water planning.