Types of Lights and Light Structures, Continued
One purpose of a range is to assist mariners in keeping their vessels on
the centerline of a channel. The range may be lighted or unlighted and
consists of two lights and daymarks located some distance apart with the
front display lower than the rear. When the range markers appear one
over the other as shown in figure 4-6, the vessel will remain within the
limits of the channel. Another purpose of a range is to determine a
ships gyro error.
Figure 4-6. Using range markers.