Abstract: For use with a ship's radar having a plan position indicator display, a navigational aid providing a selected output signal for the radar for displaying two selected pairs of a plurality of stored pairs of parallel left and right selected navigational guide lines of different direction and of different ranges-from-ship. It includes a manual direction input switch for inputting a direction for each of the plurality of pairs of guide lines, a manual range-from-ship input switch for inputting a range-from-ship for each of the guide lines, storage for each of the input directions and their associated ranges-from-ship of the pairs of parallel left and right guide lines, a manual selection switch for selecting the output signal for the two selected pairs, and a digital display for displaying the direction and ranges-from-ship of one of the selected pair.

Abstract: Marine surface radar processing equipment provides digitized target range pulses at a plurality of ranges, and includes target evaluation apparatus that comprises target leading edge signal means providing a target leading edge signal pulse at successive azimuths, and target trailing edge signal means providing a target trailing edge signal pulse at successive azimuths and initially separated in range from the target leading edge signal. The edge signal pulses describe a target envelope. The coincidence in range of a leading edge signal pulse and a trailing edge signal pulse provides a target envelope end recognition signal. The target evaluation apparatus further comprises discriminating means responsive to a maximum number of target leading edge signal pulses at successive azimuth intervals. The maximum number decreases at successively increasing ranges.