When two distinct features line up one behind the other as seen from your vessel, they form a line of position, commonly called a range line. Before GPS and other electronic fixes, mariners relied on ranges to keep centered in a channel and to know when to alter course. Even with modern electronics aboard, using a range line is a simple, reliable way to maintain situational awareness without staring at screens. Watching a range lets you judge the set of current and quickly tell safe water from hazards.
Range markers are often intentionally placed to mark the center of important channels. Onshore structures such as lighthouses, cell towers, water tanks, cupolas and flagpoles make obvious range pairs, and many natural combinations—an offshore rock aligned with a distinctive shoreline feature—work just as well. Be mindful that shoreline features change with tides and that buoys may shift from their charted positions, so fixed objects are generally more dependable than floating marks.
Traditional navigational ranges are elegantly simple: two fixed aids, one nearer and one farther, are aligned to indicate a safe track. These daymarks and beacons are built to be conspicuous and easily identified by mariners in or approaching busy coastal waters. On the Intracoastal Waterway and other confined routes, tow operators and boat pilots routinely steer by ranges. Charts show man-made ranges with solid or broken lines—solid lines indicate the navigational portion of the range, while broken lines point to where the range structures are located. Charts also list distinctive light characteristics for leading lights so they stand out from other aids.
Coming ashore in rough weather or in a crowded channel can be demanding, especially at night. A bold, unmistakable range is a huge comfort: it lets you focus on waves, sails and traffic while keeping a clear reference to the safe track. Using a range in conjunction with your instruments helps prioritize what requires immediate attention instead of becoming fixated on a single screen.
How do ranges work in practice? You are “on the range” when the two markers line up exactly. If you are to the right of the intended centerline, the distant marker will appear to the right of the nearer marker; if you are left of the track, the distant marker will appear left of the nearer one. A useful mental image is “chase the front marker” as you steer. If visualizing is difficult, try lining up two coffee mugs on a table and sway side to side to see how the apparent alignment shifts—then practice the same observation underway.
When a channel jogs and requires a course change, a skilled helmsman can follow one set of range markers to remain mid-channel, then pick up the next pair to make a smooth, gradual turn onto the next leg. Steering by range makes set and drift immediately apparent so you can intuitively compensate for current and wind without over- or undershooting your intended track.
Ranges are also valuable when setting up for docking. Aligning a mast, light pole or building peak with a closer piling or buoy gives you an instant line of position to judge how wind and current are affecting your approach. It’s far easier to correct for set before you enter tight quarters than to recover afterward.
In remote cruising grounds with incomplete charts you’ll often be directed by locals to line up two natural features to find a safe passage: “Line up the square rock on the hill with the small pipe on the cay.” Such local range instructions are time-tested and reflect centuries of seamanship. Conversely, range lines can mark danger: two shore features set in line can indicate which side is safe and which hides rocks or shoals at a glance. Fishermen commonly use two range objects to mark productive spots or known bottom features for longlining or anchoring.
Ranges have traditional uses beyond steering. Mariners historically used fixed ranges to “swing the compass” and determine compass deviation. By noting the charted true bearing of a range, applying variation to get the magnetic bearing, and then observing the compass bearing while crossing the range on different headings, you can derive deviation values. Even now, a quick check of your magnetic compass while steering a range is a sensible redundancy—electronics can fail and a reliable compass remains essential.
I enjoy gunkholing in small sailboats with minimal electronics—it’s intimate, skill-building and rewarding. Some favorite anchorages are hard to spot in daylight and nearly invisible at night. In those cases I’ll enter on a back range formed by a cell tower ahead and a lighthouse astern; when a green blink on the starboard side disappears behind a bold sand bluff I know I’m lined up and can find the opening. Two ranges in that moment provide a dependable fix, just as sailors have done for millennia.
Developing local knowledge by using familiar ranges makes anchoring, fishing and navigating confined waters easier and safer. Learn the prominent ranges where you cruise, practice steering by them, and let them augment your electronic navigation. Ranges heighten situational awareness, help you plan for set of the current and serve as a practical, time-proven tool in the art of navigation.
This article was originally published in the December 2020 issue.