Hi All
Came across this whilst doing a bit of research and thought it might be interesting to the UK contingent:
http://www.rhb.org.uk/updates/rhbupdate201404.pdf
73 de Paul G4MD
In reply to G4MD:
And even though only publlised in April 2014, by June 2014 The Tamperers have changed another summit in GM.
Andy
MM0FMF
In reply to MM0FMF:
I’m intrigued Andy tell us which one! And have we gained one, lost one or has it just been shunted sideways a bit 
Paul G4MD
In reply to G4MD:
Shunted SW about 700m along Mica Ridge.
GM/WS-053 Maoile Lunndaidh gets demoted and Creag Toll a’Choin takes its place. One of them is 1005m and the other 1005m and some centimetres.
Apprently Maoile Lunndaidh means “Bare Hill of the Wet Place”. I’m not sure what they mean by Wet Place, Loch Monar, Monar Forest or Scotland in general as all are valid!
It’s a bit remote… enjoy 
http://www.corbetteer.co.uk/munros/tr/maoile_lunndaidh/
Andy
…and the one I said has been lost.
Tom M1EYP
In reply to M1EYP:
Hush Tom I’m hoping Andy hasn’t noticed… It’s on my to-do list when next passing through Fort William…
73 de Paul G4MD
In reply to G4MD:
There are 3 or 4 changes ISTR that are queued up. We have a stack of unactivated summits still so there is no rush to update the list. I would imagine that the updates will take place when the AM has had a chance to bag them!
Andy
MM0FMF
In reply to MM0FMF:
All very interesting, but I would be more impressed if it was made clear that the RHB surveyors could distinguish between accuracy and precision. Quoting the height of a hill to a fraction of a metre is all very well but if you are not told that the newly given figure is accurate to within +/- so many metres or millimetres then you have no idea how trustworthy the new figure is.
A pity about Maoile Lunndaidhe (Mooly Lundy to us iggerant English!)which seems to have lost a couple of metres - we hill walkers should tread more gently on these hallowed hills!
Brian G8ADD
In reply to G8ADD:
You may not be impressed with their accuracy and precision, you may not even be aware of the accuracy and precision they measure to. But I’ll tell you who is, the OS themselves. When the mapping authority uses “The Tamperer’s” work, it should be good enough for anyone.
I guess that’s all that needs to be said.
Andy
MM0FMF
In reply to G8ADD:
Hi Brian
If you track down some of the actual survey reports (sometimes difficult to find but they are out there) you’ll get some idea of the rigour of the surveys. They do seem to know what they’re doing and possible errors are taken into account when deciding on the life or death of a Marilyn…
73 de Paul G4MD
In reply to MM0FMF:
Well, the OS don’t claim an accuracy of better than a few metres, so they would quite likely be impressed by, say, +/- 1 metre. That still makes quoting a height to +/- 0.1 metre a bit over-enthusiastic in my book! I’m not saying that their work isn’t good, I’m saying that we are not provided with the information to judge how good their work is, and yet we are asked on trust to change summit lists. That presumption of trustworthiness might be good enough for you, Andy, but I’ve seen enough OOPS! episodes on construction sites to make me pretty wary, and these mistakes were made by professional surveyors who do such things full time. Sure, its only a hobby, an error won’t lead to a six-figure loss, but I still think it unprofessional to quote such figures without confidence limits (or intervals if you prefer!)
73
Brian G8ADD
In reply to G8ADD:
I’m saying that we are not provided
Don’t say “we” when you mean “I” Brian.
You may not know the figures but that doesn’t mean the accuracy and precision are not known.
Andy
MM0FMF
In reply to MM0FMF:
Don’t say “we” when you mean “I” Brian.
Oh, YOU know the confidence limits, then? You certainly didn’t get them from the RHB Update.
Its quite likely that they have derived these figures, but why keep them obscure? If they are quite small, wouldn’t they trumpet them to gain the confidence of the people that they want to accept them?
73
Brian G8ADD
In reply to G8ADD:
I don’t why you are taking exception to their results Brian, maybe too many paint fumes, but you are overlooking the simple fact that we use the RHB list for the UK. Even if it’s wrong in it’s values or methods to reach those values, we use it. By definition, the RHB list is the absolute list of P150 summits in the UK and their positions and heights are as stated.
And, having read how they go about their measurements, I’m happy to believe Alan “Mr. Marilyn” Dawson measured a repeatable relative difference in the heights of the 2 peaks that gives him the confidence to de-twin the summits.
It’s not like they’ve replaced something as awesome as K2 with Billinge Hill, the summits are on common plateau 700m apart as this map clip shows.
Andy
MM0FMF
In reply to MM0FMF:
You’re missing the point, Andy, I’m not taking exception to their results for the simple reason that they give no data on which to judge their results. In a nutshell, it is the way the figures are presented rather than the figures themselves that disturbs me.
Yep, a relatively uninteresting summit plateau, but some very fine corries and ridges. I presume you still have to do it against the clock?
Brian G8ADD
You are looking at a summary document - an update sheet to the book “Relative Hills of Britain” Brian. You are not looking at the detailed survery results. I am confident that the actual detailed survery results would indeed include the important specifications of accuracy, error and precision, as the RHB survey teams are very highly regarded as Andy intimates. Why not contact RHB directly and ask them if you have any doubt?
Tom M1EYP
In reply to G8ADD:
Hi Brian,
The accuracy, or more correctly the uncertainty of any peak height is something that few people will agree on. A 5 m variation between surveyed heights has been quite normal in the past in VK for larger peaks that are inland. I have seen 10 times this difference in official government maps.
In dealing with surveyors wrt traceability and uncertainty of their measurements I found few understood the difference between precision and accuracy. They are fastidious about getting good consistency in their results and minimizing errors but some error sources are just ignored.
In VK a pragmatic approach has been taken by the Am’s. Use the height on the current Commonwealth Government map or if not available then the current State Government map. That height then becomes THE height and is deemed to be without error for the purpose of peak ordering and point score determination.
If we had the resources to do high grade surveys of all peaks today I’ve no doubt some small differences would be found.
The AM’s and MT can only go by the best available data. Unless a peak height is revised by enough to take it in or out of a scoring band it is hairsplitting to be concerned about changes of less than 1 m in every 1,000 m of height.
I know all SOTA data is wrong (even if only by mm). Bear in mind heights are recorded only to 1 m resolution and Lat and Long to 11 m.
But for the purpose of the activity, ie determining points and the activation zone, I take it as being without error.
Any other way of looking at it will lead to madness or a career in the national standards laboratory or both.
73
Ron
AX3AFW/VK3AFW
In reply to G8ADD:
These guys really know what they are doing and blog extensively about it.
The main blog is at http://mappingmountains.blogspot.co.uk/
Have a look at the spreadsheet data at Trimble Surveys Myrddyn Phillips - Google Sheets to see the accuracy they work to.
Dave - M6DFA
In reply to M6DFA:
In reply to G8ADD:
These guys really know what they are doing and blog extensively about
it.The main blog is at http://mappingmountains.blogspot.co.uk/
Thanks for the link Dave, I was beginning to regret having started this thread but that makes it all worthwhile!
73 de Paul G4MD