What navigational aids give you the fastest, easiest method for determining your location along your compass course? Learn to use the most accurate lines of position--called "ranges" or "transits".

Check your navigational chart for man-made ranges

Large harbors often have Coast Guard maintained ranges on each end of deep water channels to help ships keep lined up in the channels. Each range (also called "transit") consists of a structure built on pilings with a dayboard on top. One range structure is built (or positioned) higher than the other.

Each range carries a rectangular or triangular shaped dayboard with a central vertical stripe. As a ship or boat enters the channel, they line up the upper and lower dayboards to form an unbroken vertical line. This indicates that they are in the deepest, central part of the channel.

Know these nighttime range light patterns

At nighttime, some ranges show lights. The lower range will often carry a quick flashing light and the taller range will often show an equal interval light--three seconds of light followed by three seconds of darkness in a continuous sequence (see *Note). Keep both lights stacked one over the other to stay in the center of the channel.

*Note: always check your nautical chart; light characteristics could be different. Those described above are the most common found in U.S. waterways.

How long can you steer on a range?

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Navigational charts with US Coast Guard ranges show a solid line in the middle of the channel. This tells you it's safe to continue to use the range. Near the end of the channel, it turns into a dashed line. At this point, you will have a turn coming up, so you must find another range to use.

Expect deep draft ships to use the center of the channel to stay on range. Rule 9 of the Navigation Rules states, "A vessel of less than 20 meters in length or a sailing vessel shall not impede the passage of a vessel that can safely navigate only within a narrow channel or fairway." If large ships are present, stay to the right of the channel center for safety.

Look for natural ranges

If Coast Guard or Government maintained ranges aren't present, look for natural ranges. Natural ranges are formed when two objects line up with your compass course. A piling and the edge of a roof, a church spire and a radio tower or the left side of an island and a buoy. Highlight charted natural ranges along your course. Indicate that point along the track where you must stop using the range (as described above).

Follow These Steps to Get Back onto Range (Transit).

Wind, seas and current can combine to make steering on a range a challenge. Use these tips to determine how to regain range if one of these natural forces pushes you off your sailing course:

Ranges (Transits) Ahead of the Bow.

1. Concentrate on the lower range.

2. Lower range to the left? Steer left to get back onto the range-line.

3. Lower range to the right? Steer right to get back onto the range-line. 

Ranges (Transits) Astern (also called "over the shoulder" transits).

1. Concentrate on the higher range.

2. Higher range to the left? Steer left to get back onto the range-line.

3. Higher range to the right? Steer right to get back onto the range-line.