Precision Guidance with Multi-Layered PEL-6 Lead Light System in Durban, South Africa
As part of the Durban Harbour deepening project, engineers faced a unique challenge: how to deliver 6 nautical miles of daytime visibility using PEL lead lights—including oscillating boundaries, never before deployed in a multi-tiered array.
Background & Challenge
The Port of Durban, one of Africa’s busiest ports, required a new lead light system for vessels navigating both a temporary dredged channel and the final deepened entrance channel. The objective was to provide:
- Minimum 6NM of daytime range
- Precise lateral guidance using oscillating boundary technology
- Flexibility to adapt the system for both temporary and final channel alignments
- Visual unity across multiple light sources for safe navigation
Traditionally, a single 5° PEL light delivers around 3NM range for red and green sectors in daylight. Reaching 6NM would require stacking multiple lights—a method previously used with fixed-sector PELs, but never with oscillating boundary lights, which require perfect synchronisation to appear as one cohesive unit.
Solution for High-Range Day Navigation – Synchronized Stack of 6 PEL-6 Lanterns
To achieve the desired range, the project deployed a PEL-6 lead light system with six vertically stacked PEL-6 units, each with a 5° horizontal beam angle. Sabik engineers implemented a 6-axis motion control system to synchronise the oscillating boundaries across all units. This innovation enabled:
- Combined boundary resolution of 1.5 minutes of arc, close to the 1 arc minute of a single high-precision PEL light
- Seamless operation as a single visual signal—essential for mariner confidence
- Flexible channel width adjustments by changing the fixed filter plates only, with no need to replace colour filters
To coordinate day/night transitions, a single Light Dependent Resistor (LDR) was used to control intensity shifts across all six lanterns simultaneously. Each oscillating boundary was powered by a linear actuator driven by a voice coil, achieving positional accuracy within 50 microns, monitored by a Galil 6-axis controller.
The control system also ensured safe operation: if one or more units fall out of synchrony, they are automatically shut off to prevent false guidance. The system then attempts to re-synchronise the inactive units continuously.
Outcome: First-of-Its-Kind PEL-6 Lead Light System Offers New Benchmark in Port Entry Safety
The Durban Harbour PEL-6 lead light system represents a technical milestone: the first deployment of a stacked, synchronised array of oscillating boundary sector lights. The port now benefits from:
- Unprecedented 6NM daytime range with sector guidance
- A fail-safe synchronisation system
- Adaptability between temporary and permanent navigation channels
- Efficient, cost-saving design for future reconfiguration
This innovative solution provides a new standard for precision navigation in complex port entry scenarios.
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