Line 'Em Up: Navigating With Natural Ranges

Among the tricks and techniques in the navigation toolbox, few are as foolproof as the natural range.

- Capt. Daniel S. Parrott

Also known as a transit, a natural range exists when two charted objects — one closer and one farther away — visually align and appear to meet, forming a line of position, or LOP.

Whereas a bearing requires a compass, and raises questions of accuracy and skill, a natural range is indisputable. When the two charted objects visually form a line, you are on that line and nowhere else — end of story. Natural ranges are so reliable that, in an effort to imitate nature, ports around the world for centuries have erected lighted and unlighted ranges to guide vessels. These consist of two navigation aids, one closer and one farther away, the farther one being higher than the nearer one. When the two structures or lights line up, you’re in the channel.

Natural ranges abound. When the shoreline edges of two islands align, it’s a natural range. It’s much the same when an isolated rock lines up with a ledge or a point of land. Natural ranges might include unnatural objects, such as the end of a jetty lining up with a water tank, church spire, lighthouse, radio tower or any combination of distinct, charted features. So long as the features can be identified on the chart and in the real world, they are useful allies in confirming your whereabouts.