Sea state

Low (calm) sea state

Multi-path signals can either enhance or reduce signal strength, depending on the target range and characteristics. The detection range for targets at optimum Gain, assuming that the targets are not obscured by the horizon, will depend on a target's characteristics and the propagation (ducting) conditions. In some circumstances, ducting will permit visibility of targets at much longer ranges than could normally be expected. A radar antenna physically located in a higher position will normally increase the range of detection, but may deteriorate performance in adverse clutter conditions.

Raymarine’s Pathfinder radar transmits multiple pulse lengths, which provides enhanced detection.

High (rough) sea state

Rough sea: As sea roughness increases, target detection is less affected by multi-path effects, but more adversely affected by sea clutter. The nature of the signal reflected from a wave is different than the signal reflected from a target. Processing techniques assist in making the target more visible. Clutter signals increase when viewed upwind. Although sea clutter signals can look like actual targets, as most clutter is in the form of sea spikes, they will fail to correlate.

The rapid movement of high speed ships (especially on shorter range scales) may fail to correlate, impacting target detection. Very large waves may also obscure targets, and in these conditions, targets may not be visible to the radar system.

High winds will cause small targets (e.g. buoys and yachts) to heel over, reducing the reflected radar signal and therefore negatively impacting target detection.