North Hoyle Windfarm Report

6 MCA Radar trials

6.7 Bearing Discrimination

6.7.1 Objectives and method

The objectives of these trials are similar to those of range discrimination, but in azimuth rather than down range.

Hoylake lifeboat traversing East and West of turbine 1, with "Lill Cunningham" stationary 3 nautical miles South of turbine 1, its radar set to the 3 nautical mile range and "Lady of Hilbre" very close to the northerly side of turbine 1, the size of the cross-range arc of the returned echo of turbine 1 was measured using the radar’s bearing markers. The course is illustrated in Figure 6-13.

"Lady of Hilbre" could not be visually distinguished from the echo of the turbine therefore proceeded slowly on a westerly course until its echo on "Lill Cunningham"s radar visually separated from that of the turbine. "Lady of Hilbre" then proceeded on a reciprocal easterly course until its echo on the radar on "Lill Cunningham" again separated from that of the turbine. Radar bearings and ranges of "Lady of Hilbre" were recorded at both of these instances. The full procedure was recorded by video camera. It should be noted that the radar beam width, unlike pulse length, will not vary significantly with the range to which the system is set and thus, the bearing discrimination in degrees will be effectively a constant. Cross-range response widths can be calculated for other ranges from the turbines at which the search vessel ("own ship") may lie (see Figure 6-7).

Figure 6-13: MCA bearing discrimination test schematic

6.7.2 Results of the trial

Full separation both west and east of turbine 1 was achieved at an angle of 4 degrees at the observation range of 3 nm. This angle is measured from the centre of the turbine echo to the centre of the target echo and equates to a distance of 388 metres.

It should be noted that the target would only show as a distinct and separate echo when some 385 metres clear of the turbine tower and therefore it would not be detectable for a distance of 770 metres from one side of the turbine to the other. As can be appreciated, the echo of a target travelling through this turbine array would be separate from nearby turbines and trackable by ARPA for only short periods of time and distance.

The results are illustrated in 6-14.

Figure 6-14: Bearing discrimination trials results