Marine Glossary

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range

Range has many meaning in navigation, some are similar, others not. It is usually the context of the usage that will determine which of these definitions apply.

n. 1. Two or more objects in line. Such objects are said to be in range. An observer having them in range is said to be on the range. Two beacons are frequently located for the specific purpose of forming a range to indicate a safe route or the center line of a channel. Such an arrangement is called a NAVIGATIONAL RANGE. On a navigational range, the more inland daymark or light is higher than the forward one that is closer to the observer.

When any two charted objects are in alignment, that is called a NATURAL RANGE. Ranges are one of the most accurate lines of position possible for a piloting fix. Often we can use a noted range to maintain a straight course, even if the objects are not identifiable on the chhart.

2. Distance in a single direction or along a great circle. The phrase "range and bearing" means distance and direction in all marine navigation applications.

3. The extreme distance at which an object or light can be seen is called VISUAL RANGE. When the extreme distance is limited by the curvature of the earth and the heights of the object and the observer, this is called geographic range; when the range of a light is limited only by its intensity, clearness of the atmosphere, and sensitiveness of the observer’s eyes, it is called luminous range.

4. The extreme distance at which a signal can be detected or used. The maximum distance at which reliable service is provided is called operating range. The spread of ranges in which there is an element of uncertainty of interpretation is called critical range.

5. The distance a vessel can travel at cruising speed without refueling is called CRUISING RADIUS.

6. The difference in extreme values of a variable quantity. See also RANGE OF TIDE.

7. A predetermined line along which a craft moves while certain data are recorded by instruments usually placed below the line, or the entire station at which such information is determined.

8. In radar applications the full scale setting of the radar screen, or the distance to a target from your vessel, or the distance between two targets.

See also Tricky Terms in Navigation.