Module 12 - Visual Aids to Navigation
Sector Lights in Navigation: Red, White and Green Explained
Quick answer
A sector light shows red, white, or green over different bearings. The colour you see tells you whether you are in the planned sector, near a channel edge, or standing into danger.
- White often marks the preferred safe-water sector.
- Red or green sectors usually warn that you have moved out of the intended line.
- Always check the chart: sector colours are guidance, not a replacement for pilotage planning.
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.
A colour change is useful feedback: it tells you that your bearing from the light has moved into a different sector.
Key points
- 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
Common mistakes
- Treating all white sectors as automatically safe without checking the chart.
- Forgetting that the colour depends on where your boat is relative to the light.
Practise pilotage with visual aids
Sector lights make more sense when combined with leading lines, clearing bearings, buoyage, and safe-water planning.