What does a fixed range marker on a radar system indicate?

A fixed range marker on a radar system is used to indicate a specific distance to a target. This marker helps the navigator understand how far away objects are within the radar's range, enabling more accurate navigation and situational awareness. By setting these markers at predetermined distances, mariners can easily gauge the proximity of other vessels, land masses, or navigational aids relative to their own position.

In the context of the other options, the maximum detection range pertains more to the overall capability of the radar system rather than the fixed range markers themselves. The exact speed of a vessel is determined by other measurements, typically involving a speed log or Doppler radar techniques, rather than using range markers. Lastly, the depth of the water is ascertained through soundings or depth sounders, which are distinct from the functions provided by fixed range markers on radar. Thus, the primary role of the fixed range marker is to provide a clear reference for distance to a target, making it crucial for effective navigation.