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Break of Slope

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I'm reading a navigation book which refers to the 'break of slope' and this appears to have something to do with how plateau are shown on OS maps. I've tried looking this up in the index my other books, including UNM, and googling it and can't find any reference to what a break of slope actually is and what it looks like on an OS map.

Any thoughts?

captain paranoia:
My guess would be that it's the rate of change of slope; that would make sense for the transition from plateau to slope.  And can give useful navigation clues.

Hugh Westacott:
Who is the author and what is the title of the book, Ian?

I grow old...I grow old, I shall wear the bottom of my trousers rolled. T.S.Eliot

Thanks for the suggestions.
 It's in Kevin Walker's book Navigation, page 56 there is a picture labelled Pen Allt-mawr and the text says ' The contour pattern reflects the shape of the landscape. Here the plateau and the surrounding steeper slopes are very obvious both on the ground and on the map. The plateau is defined by a marked 'break of slope'. Location SO 214 226.'

Not helped by the fact that as far as I can see either the name or the GR is wrong. Pen Allt-mawr has what I think is the larger plateau but its GR on SatMap Xpedition software is SO 206 242, SO 214 226 is on Pen Cerrig-calch - I was looking on the map for some sort of break in the contour lines but I suspect CP has it nailed.

Hugh Westacott:
Thanks, Ian.

Unfortunately, I don't have a copy of the book in question although I do have another of his books entitled Mountain Navigation Techniques published in 1986 but I cannot find any reference to 'break of slope'. I'm sure that CP's explanation is correct; it means nothing more than a marked change in the steepness of the slope.

And I'm sure that you are right to state that the author gives an incorrect grid reference. This is confirmed by an examination of the two locations. Pen Cerrig-cach has a slope running from the summit so could not reasonably described as a plateau whereas Pen Allt-mawr does. I'd go further and suggest it would be more accurate to describe the latter as a 'level summit'; the term 'plateau' is generally used to describe an extensive area of high, level ground.

I note that Kevin Walker suggests in Mountain Navigation Techniques that small lakes and pools are useful in micro navigation. But he seems unaware that bodies of water have to be at least ten metres wide to be depicted on Explorer maps, and fifty metres wide to be shown on Landrangers. I discovered this many years ago after I complained to the Ordnance Survey that a pool I encountered when navigating in Scotland in limited visibility was not marked on the map which caused me considerable worry and confusion.

I grow old...I grow old, I shall wear the bottom of my trousers rolled. T.S.Eliot


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