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John Michell lecture
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tiompan
tiompan
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Re: John Michell lecture
May 08, 2016, 08:28
AN said “If you correct John Michell's grid bearing of 66.5 degrees to a true north bearing it comes out as 69.23 degrees which is very close indeed to the 69.36 degrees that I calculated.”

What has confused you is grid convergence ,it’s awkward but if you get it wrong it really messes things up .Simply put “: “It is positive when Grid North lies east of True North”.
“.In this case grid north is west of true north meaning it is negative i.e. you take away the convergence from the bearing to find the azimuth . so it’s 66.5 minus convergence not plus .
The upshot is that the bearing of 66.5 is very close to 5 degrees out from the actual azimuth (68 degrees ) that aligns with the sun on the horizon at May day .
n.b. Bearings are related grid north ,azimuths to true north . hence 2 quite different figures for the same event .

You had earlier said that “John Michell did not make mistakes with measurements.”
Joining up points on a map with a straight edge and pencil does not involve any measurement ,in fact there is little of any measure in book . But we have one here i.e. where Michell says “It may therefore be significant that a line drawn on the map through Men an tol towards the May day sunrise at an angle of 66.5 degrees “
Whichever way you look at it there has been a mistake in measurement .
The May day sunrise of 66.5 degrees is a measurement ,it is also wrong .
The line drawn on the map is on a bearing of approx 66.5 degrees but it does not point to the May day sunrise .The bearing for the sunrise is 63.4 degrees .
Another monument supposedly on the “alignment “ is Bosullow Trehellys ancient settlement This site ,another of the type that doesn’t fit into the three main considered types provides a target a100 yards but it also happens to have yet another grid ref a whopping 1100 plus yards from the correct spot . It’s not as if you can miss it , it’s a settlement not a stone .

Again ,this is new ,or at least I am unaware of anyone having pointed this out previously ,are you ? , and we still haven't covered all the older problems .
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