Abstract: Apparatus for detecting the position of a vessel in a broadcast image of the radar scan in a radar monitored area includes a television monitor for displaying a broadcast image of a radar scan of the area, and a controllable reflector for varying reflection of the radar waves impinging thereon from the monitoring radar to produce identifiable signal components in the broadcast image of the radar scan received on the television monitor. This controllable reflector may be actuated by the vessel operator to vary the reflection of the radar waves and produce variations in the broadcast image to enable the operator to identify the position of the vessel in the radar scan image appearing on the monitor. The monitoring installation includes a monitoring radar transmitter/receiver, and a television transmitter televising an image of the radar scan. Desirably, it includes a scan converter which receives the signals in polar coordinate form and provides rectangular raster signals with X and Y coordinates.