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Marine Pilotage Planning - Clearing Line, Transits and Safe Track

Sections: Safe Track and Clearing Line Transits Pilotage Planning

Marine pilotage involves the use of clearing bearings in a pilotage plan.

The art of pilotage is the navigation by eye, compass, and chart, when in sight of land and to determine a series of safe tracks, confirming at any time that the boat is on or close to these tracks, without plotting a position on the chart. Marine pilotage is used when entering or leaving harbour, when time does not allow plotting of fixes on the chart and where an error of a few boat's lengths can be critical.

Safe Track and Clearing Line or Clearing Bearing

Two types of bearings when piloting are:

  • the bearing of the safe track between hazards which is the course followed through constricted water, and
  • the other is a clearing line which defines the boundaries of a safe zone.

Clearing bearings are a proven method of coastal navigation. They are simple and provide a quick visual reference of the ships position in relation to shoals, isolated dangers or wrecks. Clearing bearings are determined and prepared whilst planning your voyage.

Having been identified on a chart or harbour plan, bearings of a safe track or a clearing line are measured using the hand bearing or steering compasses. When the boat can be pointed at the object, the steering compass is used; otherwise use the hand bearing compass. However using a transit bearing is simpler and can be more accurate.

Navigation Transit Bearing

When two objects are in line, they are known to be in transit. If seeing two objects in transit, the boat is someplace on the extension of the imaginary line or transit bearing that joins them. When the objects are identified on the chart, there is very useful single line of position.

Transits need not be in line to have some use in providing a transit bearing. Two objects not quite in line, said to be open or closed, can be used to define a clearing line or clearing bearing. The boat is steered keeping the objects open or closed avoiding a danger to the side of the safe track.

Choosing Transits

Transits usually are man-made objects such as posts or beacons specifically constructed to mark safe passages into and out of harbours. Rocks or headlands may be used as transits provided they are clearly visible and identifiable on the chart, at a reasonable distance apart and not too close to the boat.

If selecting objects in the water, such as rocks or posts, allow for their changing appearance with tide height. Individual rocks may be difficult to identify in rock-strewn areas, along with man-made leading marks against a background clutter of shore-side buildings.

Pilotage Planning

Before reaching the pilotage area, study the chart and harbour plans then determine the safe tracks finding suitable transits near the course. The prominent transits are marked on charts or described in harbour plans.

Pilotage planning requires identifying all navigation marks that are expect en route then draw in the intended track while checking for close by dangers. Make a note of all the light buoy characteristics of the track when piloting at night and note down the key details for use in a pilotage plan.

During piloting, avoid using the chart on deck because of the difficulty of keeping it under control in a breeze. If the course is from north to south, there can be difficulty in interpreting the chart upside down. Prepare a pilotage plan to use on deck including the bearing of the each leg of the route, with distances between turning points and navigation marks.

Start the pilotage plan from the bottom of the page and work up. Courses, navigation marks, and other important details are presented relative to the direction which is travelled. Note all marks or other significant features that is expected to be seen, together with their distance off the track and the bearings of any clearing lines.

If piloting at night, pilotage planning requires making a note of the characteristics of all the lit marks in the area. Double-check each piece of information avoiding complacency, and aim to move from one known safe location to the next.

Marine pilotage and the use of clearing bearings and a clearing line to navigate.