What function does a Variable Range Marker (VRM) serve in navigation?

The Variable Range Marker (VRM) is an essential tool in navigation that serves the primary function of providing a controllable range ring on a radar display. This function allows navigators to set specific distances from their vessel to monitor and mark points of interest, such as other vessels, navigational hazards, or predetermined waypoints. By adjusting the VRM, a navigator can clearly see at what distance an object is from their position, helping with turn planning or to visualize the approach to a particular point, facilitating safe navigation.

In the context of navigation, this ability to mark turns and monitor distances is crucial for maintaining a safe course, especially in crowded or potentially hazardous waters. The use of a VRM in conjunction with other navigational aids enhances situational awareness and decision-making on board.