Which map indicator provides a fixed and precisely known elevation value?

Which map indicator provides a fixed and precisely known elevation value?

• A. Benchmark
• B. Contour line
• C. Isoline
• D. Grid line

Answer: (A)

A benchmark provides a fixed, precisely known elevation because it is a physical reference point whose exact height above a standard datum (like mean sea level) is recorded and used for accurate surveying. This marker stays in the same spot and has a documented elevation, so land elevations on maps can be tied to an absolute value.

Contour lines, by contrast, connect all points that share the same elevation, but they don’t give you a single exact height at a specific point unless you read a labeled value somewhere along or near the line. Isolines are general lines of equal value for any measured quantity, not specifically tied to a fixed height reference. Grid lines are for locating positions in a coordinate system, not for providing elevation. So the benchmark is the tool that delivers a fixed, precisely known elevation value.