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48.


There is a significant difference in path loss between the turbine tip at the LoS height and a point 20m below the tip (-20m), suggesting anything 20m or more below the LoS height can be ignored from the calculation.


49.


156dB path loss is the equivalent to a free space path length of 1,200km and would require an RCS gain at the turbine tip of 45.8dB to meet the earlier sensitivity calculation, equivalent to an RCS of 175m2 at the turbine tip.


50.


Considering the rapid increase in path attenuation below the blade tip, the turbine would not be expected to be detected by the radar at the LoS height.


51. At 20m higher than the LoS height (+20m), the required RCS to produce a detectable signal falls into the region 20m2 to 50m2, which is entering the range where the radar might reasonably be expected to begin to detect the turbines.


52. 53.


If the turbines exceed the LoS height by more than a few metres, then a technical mitigation solution may be required for the MOD Trimingham radar.


In the absence of detailed technical data on the TPS-77 radar, calculations illustrate that Pd and LoS are effectively the same. Radar LoS at the closest point of the East Anglia THREE site is 195m. Turbines of 195m or less would be below the LoS of the Trimingham radar and would require no further mitigation.


16.6 NATS Cromer Radar 54.


55.


The closest point of the East Anglia THREE site is 52.12NM (96.5km) from Cromer radar.


There is no intervening terrain to provide any screening of the East Anglia THREE site, however, earth curvature provides significant screening of the East Anglia THREE site. The absence of terrain screening means that the edge of radar cover follows an arc.


16.6.1 Radar Line of Sight 56.


Initial assessments carried out established the radar Line of Sight (LoS) to various turbine heights across the East Anglia THREE site. These are reproduced in the following diagrams. Radar LoS is indicated by the magenta shading.


Preliminary Environmental Information May 2014


East Anglia THREE Offshore Windfarm


Appendix 0 Example Page 13


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