What does the bottom line of an RHI scope display indicate?

The bottom line of an RHI (Range Height Indicator) scope display indicates the line of sight (LOS). This component of the RHI provides critical information about the observer's position relative to the targets being displayed. The line of sight represents the direct path from the operator to a particular point in space, which is essential for accurately interpreting the data shown in the display.

Understanding the line of sight allows operators to assess the elevation of targets and their distance in three-dimensional space, facilitating better decision-making in various operational contexts, such as aviation or battlefield surveillance. Proper interpretation of the line of sight can influence tactical maneuvers and the effectiveness of response actions.

The other options do not accurately describe the function of the bottom line in an RHI display: target range pertains to distance measurements, wind direction is a meteorological concern supplemented by other instruments, and operator altitude refers to the height of the operator relative to sea level, which is not conveyed by the specific feature in question.