How are range markers used in navigating a channel?

• A. Line up for safe navigation
• B. Indicate channel depth
• C. Mark position of lighthouses
• D. Show mariner's preferred route

Answer: (A)

Range markers are a pair of fixed marks, a front range and a back range, set along a safe line through a channel. When you line them up visually—keeping the front and back range in a straight line along your intended path—you know you’re on the proper centerline for safe passage. If they don’t line up, you adjust your course toward where alignment would occur, helping you stay clear of shoals and rocks.

They don’t convey channel depth, so depth gauges or sounding charts are the way to judge that aspect. They aren’t markers for lighthouse locations, and they don’t prescribe a “preferred route”—they indicate the safe line to steer through the channel. In practice, especially in Maine’s Nor’easters and variable currents, using the range markers to maintain alignment keeps you centered in the channel and away from hazards.