LIKE most opponents of the Navitus Bay windfarm, Rodney Pattisson needs to brush up on his arithmetic.

He tells us (Letters July 11) that from Sandbanks beach a 200m Navitus turbine ‘would appear three times the height of Old Harry’. This statement Rodney Pattisson terms ‘accurate’ and it was repeated as a picture caption. But is it accurate?

I reckon the shortest bit of Old Harry, the slender stack at the end, is about 22m tall. It is 5.34km from Navitus Viewpoint 15 on Sandbanks beach which would be 21.2km from the nearest turbine.

Viewed from the beach, the horizon would be about 6km away shielding 18m of the turbine’s base from view.

Given these numbers, if the nearest turbine is fully visible, I make the ratio of apparent height to be 2.08 to 1.

Rodney Pattisson’s assessment of 3 to 1 is thus inaccurate enough to be called plain wrong.

DR MARTIN RODGER, Bloxworth Road, Poole