Sunday, 30 March 2014

The History of Welsh Hill Lists



The History of Welsh Hill Lists – Part 2

The Early Years
1911-1940

1912 John Rooke Corbett


Only a year after the ‘Twenty-Fives’ had been published an update to the list appeared.  During the intervening year members of the Rucksack Club had scrutinised maps of the time and come across seven omissions from the original list.  Five of these are in England, including the infamous Pillar Rock and The Knowe on Harter Fell, which was believed to be the only twenty-five Mr Minor had not been up.

Although input had been received from a number of club members the update was assigned to John Rooke Corbett with his initials J.R.C. appearing at the end of the article.  The update to the ‘Twenty-Fives’ appeared on page 166 in the 1912 publication of the Rucksack Club Journal Vol II, No. 2 and is entitled ‘Excursions’.

After an introductory paragraph with the lead heading of Twenty-Fives, the mountains are listed.  These are indented from the text of the article and only appear in name, with no height given.  Some have a brief explanation to their whereabouts.  Of the seven listed only two are in Wales, these are Cader Berwyn, on the Berwyn Ridge; and Pen-y-Nantllyn, between Gader Fawr and Waun Fach.  Corbett explains that there is a case for the inclusion of Gallt-y-Gogof, which the Ordnance Surveyors had given a height of 2,499 feet above sea level.  He explains that the mountain could be thought of as being 2,500 feet high at low tide as unsatisfactory, as it is always low tide at some point on the coast of Britain and high tide at some other point.  Other thoughts are also expressed as it was countered this peak should be included if any person more than two feet high was to stand on its summit, then the greater part of their anatomy had attained the required altitude.  The conclusion being that the peak might be counted as a Twenty-Five if when standing on the top, the person should leap at least one foot into the air.

The 1912 one page update to John Rooke Corbett's 'Twenty-Fives'

The 1912 article set a precedent that many a hill list author over subsequent years would follow, as it is the first update to a hill list that ever appeared, it would not be the last to the list known as the ‘Twenty-Fives’, but for that we will have to wait another seventeen years.  After Corbett’s 1912 update to his original list fourteen years were to pass before the next list appeared.


Next installment due on the 30th May 2014


For the Preface please click {here}

For Part 1 please click {here}

For Part 3 please click {here}









Tuesday, 25 March 2014

Guest Contributor - Phil Newby



Introduction

I have approached a number of people to write articles, but if readers would like to contribute an article please contact me. The only two stipulations I make are that the article has to be hill related and that I don't end up in court through its publication! Otherwise the choice of subject matter is down to the Guest Contributor.



 Guest Contributor – Phil Newby

Phil Newby - Website host of Haroldstreet, one of the leading and innovative websites for hill baggers
I started www.haroldstreet.org.uk in January 2001 as a personal project to learn to build a website.  I focused it around my Christmas present for that year which was a basic GPS unit (intended to help me improve my navigation skills), and my ongoing interest in hill bagging and mountain walking in general.

At first, the site was very basic and little more than a collection of GPS files to download.  These included GPS waypoint files for Munros and Wainwrights, and GPS routes of walks that I had recorded while out in the field.  There was also a bit of a photo blog relating to my walking trips in Scotland & the Alps, wild flowers, and my passing thoughts on various bits of walking gear.  These still continue as an aside to the main site. 

Towards the end of 2002 I was approached by John Davis to host a file of GPS waypoints for the OS Triangulation Pillars he was compiling.  This same file went on to become a starting point for Teasel's wonderful trigpointing-UK website.

Over the years, I continued to add more and more lists of various hills from a wide range of web-based sources.  However, the effort of keeping these lists up to date, and cross referenced for accuracy & consistency became massively onerous.  The work increased exponentially in complexity with every new list added.  Eventually, I discovered the brilliant hills database maintained by Chris Crocker and team, and with their permission discarded all my own separate lists in favour of their far superior efforts and capacity for constantly improving the accuracy of the data.

Once I had reconfigured my site to use the Database of British & Irish Hills dataset to generate the GPS waypoint files dynamically, I converted the Trig-point data from John to work as part of my website's underlining database too.  I then connected many of the trig points to their nearest hill.  It was a bit of a revelation to discover that most trig points were not on recognised hills at all, and that many of those that were, were some distance from the true summit.  In the end, I settled on an arbitrary proximity of 200m for lumping a trig point and a hill summit as being the same "bagging entity". 
    

Haroldstreet home page with choices ranging from on-line tick lists to shared GPX files
The use of a database behind the website also opened up the possibility of adding Google mapping to all the pages.  This was a significant steep learning curve for my infantile website skills but also a very enjoyable challenge.  After this, I soon realised I could also use these hill lists as simple tick-lists to track my own hill bagging progress, and with just a bit more work it was easy to extend this functionality for any of the visitors to my site through a simple membership scheme.

Membership also provided opportunities for other people to share their GPS walking routes and waypoints with the virtual world, as well as record comments and photos against the hills, routes and trig points on the site.  This has made the site content much broader and more interesting than I could ever have achieved on my own.

A major coup for the website was when Phil Brady asked me to host his famous Ordnance Survey Frequently Asked Questions pages and his amazing OSGB Excel conversion spreadsheets.  These Excel routines convert latitude and longitude to and from OS references, compute bearings and ranges, compute variations from north, import and export GPX files, show data on Google Earth and convert postcodes.  These pages are held at www.haroldstreet.org.uk/osgb/.

More recently the site has again benefited from collaborations with Rob Woodall, Nick Wakelam and Bernie Hughes in adding some more hill lists. www.haroldstreet.org.uk hosted the Tumps (P30s) and the Synges earlier than the Database of British & Irish Hills, and more recently has added the Yeamens and Dewey Notables.  We are now looking at working on a new collaboration around the Lakes Minor Prominences (LaMPs) for the New Year.   

I'm also always open to adding a new hill list if anyone is motivated enough to do the work of getting me the data in a format that is similar to that used by the Database of British & Irish Hills and ideally cross-referenced to their existing hills.


www.haroldstreet.org.uk statistics for the year 2013:

·         more than 51,000 unique visitors/per annum 

·         more than 347,000 pages viewed/per annum 

·         more than 11,500 GPS Files downloaded/per annum 

·         more than 2000 members have registered (and successfully logged in)

·         more than 138,000 members' hill & trig point bagging ticks are recorded

·         more than 770 walking routes have been submitted by our members


The site will always remain a not for profit venture and relies on a small but consistent stream of donations, and some modest advertising revenue to pay for its ongoing internet hosting costs.

The site has benefited massively from every collaboration with the site users in its continuing evolution; whether this has been a member's feedback on a minor issue, a comment on a missing trig point, submission of each GPS route, or help compiling of an entire new list of hills for the site.  So my thanks go to every contributor and donor who has helped me make www.haroldstreet.org.uk what it is today.


The Welsh Marilyns page on Haroldstreet
When asked why he used Haroldstreet, Rob Woodall said "Haroldstreet has become a key hill bagging tool for me over the last year or so. I had been vaguely aware of it for years, but when a friend started using Haroldstreet as her primary trig bagging resource, I quickly discovered its merits - in my case mainly as a practical tool for use in parallel to the much more detailed and labour-intensive hill-bagging and TrigpointingUK sites. 

The first thing that struck me was how easy it is to tick things off, using either the list interface (for lists already completed) or the map interface for ongoing projects. I had all my several thousand logs ticked off within 2 or 3 evenings! The speed is largely because there is no date logging facility (users wanting to record their visit dates will need a parallel system for this).Then the ability of the main map page to zoom in to 1:25,000 OS mapping is a boon for planning purposes, as is the ability to switch to aerial photography to verify that the forest rides really are where the OS say they are, before doing battle with the sitka spruce! This is extended by easy linking to other related sites for even more detail, such as Geograph.org.uk for 1:10,000 mapping and photos. Another powerful feature is the SQL functionality. Many websites tend to do their data querying in the background. On Haroldstreet it is possible for a non-programmer like me to intuitively customise the URL to view / filter hills e.g. by height band and / or re-ascent, or to combine or contrast lists.

Another plus for me is that Phil as site owner is always open to new ideas and lists. It's fun and quite a privilege to be able to contribute to what is an excellent and very usable website."

Wednesday, 19 March 2014

Corronoher (R 409 310) – New Irish Marilyn



In September 1997 TACit Tables published The Hewitts and Marilyns of Ireland, these two lists were compiled by the late E. D. ‘Clem’ Clements.  As this post relates to a new Irish Marilyn all figures and detail quoted will relate to the Irish Marilyns and not the Irish Hewitts.

The TACit Press publication for the Hewitts and Marilyns of Ireland
In all Clem listed 453 Irish Marilyns with a further 43 SubMarilyns also listed.  A Marilyn is any hill with a minimum of 150m of drop on all sides; a SubMarilyn is any hill that misses out on being a Marilyn by less than 10m of relative height (hills with 140m – 149.9999m of drop).

The SubMarilyn list appears on pages 30-32 of the TACit booklet.  Appearing on page 31 of the Sub list is Corronoher, not a great hill in terms of absolute height as it is given a 273m spot height on Ordnance Survey of Ireland (OSI) maps, but in terms of relative height the hill is quite substantial as Clem listed it with a drop of c 145.  The ‘c’ preceding the 145 figure implies that the drop value was estimated from col contour interpolation.  Adjoining this hill’s detail is a reference number of 277.  This number is part of an extensive Notes section that appears at the back of the booklet and was compiled in conjunction with the TACit series Editor; Dave Hewitt.  The note against Corronoher states ‘Details updated just before publication from the new OS65’.  As the OSI were updating their then current ½ inch to 1 mile series with the 1:50,000 series of maps The Irish Marilyn publication was being compiled during the latter years of these updates. 


Before continuing it is probably best to give the relevant map details for the hill:


Name:  Corronoher

Summit Grid Reference: (R 409 310)

Summit Height: 273m

Map:  Discovery 1:50,000 number 65

Section:  48B

Col Grid Reference:  R 438 334 / R439 333

Col Height:  c 120m - c 130m


Clem had estimated this col to be 128m high, giving a drop value of c 145m.  Interpolation of col contours can sometimes be a tricky business, but independent analysis of Clem’s estimated col height gives a higher drop value.  This is substantiated by Clem himself who later re-evaluated this drop figure.  The details to this will be given in a following paragraph.

Once the list to the Irish Marilyns was published in September 1997 it would only be another 9-10 months before an update appeared.  This update was published in The Angry Corrie number 37, with the article dated June-July 1998.  In all there were 33 changes to the Irish Marilyns listed, much of this related to a tweak in height and / or grid reference.  However, more interestingly was the inclusion of two new Marilyns; both are in Section 54B, they are; Cullenagh Mountain (S 498 895) and Cullahill Mountain (S 379 710).  The former is 317m high and was elevated to Marilyn status with a listed drop of 153m (it had previously been listed as a Sub with c 145 of drop), the latter is 313m high and was included as a Marilyn with 151m of drop, this hill had not previously appeared even as a Sub.  This update increased the total of Irish Marilyns by two to 455 and the Irish SubMarilyns decreased from 43 to 41 with the inclusion of Cullenagh Mountain as a Marilyn from Sub and the exclusion of Dho Bran (S 789 400) with under 140m of drop.

Over subsequent years there have been occasional changes to the list of Irish Marilyns, including Knockalla Mountain NE Top (C 247 355) being twinned with Knockalla Mountain (C 235 342), and the demotion from Marilyn status of Knockiveagh (J 182 378) and Croghan Hill (N 482 331).  But no new Irish Marilyn seems to have appeared since Clem’s Angry Corrie update of 1998.  After these updates it left the total of Irish Marilyns at 453.

Clem passed away in October 2012; he left instruction for his hill lists / card index to be left to David Purchase, myself or Rob Woodall.  The Executor to his estate asked me to be custodian of these, including all of his hill related papers and his photographic slides.  I then invited the other named people; David and Rob, to form a Legacy Committee with the intention to safeguard all of Clem’s hill related papers and eventually make provision for this to be suitably archived.  During this process we invited Mark Trengove to join as he had dealt with Clem on all of his European listings and had communicated with Clem through letter for many years, as had the other Legacy Committee members.  Since formation we have been joined by Barbara Jones, a Marilyn and Trig bagger who knew Clem from his days in Guildford.  We have subsequently invited the DoBIH editors to join the Legacy Committee on a rolling basis, they declined the offer.

Clem, far left, 12th June 1947, on summit of Buchaille Etive Mor
Clem on one of his many cycling adventures


Clem viewing a video of Mark Trengove being interviewed
Part of the responsibility of being in the Legacy Committee is to take over as custodian author for the listings that Clem left for us.  It is David and I who have adopted this role for the Irish Marilyns, whilst Mark deals with Clem’s European listings and Rob the Clem / Yeamans.

Clem’s hill bagging and listing was only one aspect of his life, but it is the subject I know most about so I’ll try not to diverge as I may start to get my facts muddled.  During the latter years of his life Clem was a great letter writer, communicating with many people from the hill bagging community, some of this communication centred around correspondence with Eric Yeaman, Alan Dawson and Dave Hewitt, other letters were to Rob, whilst Jonathan de Ferranti also corresponded with Clem, as did I.  All manner of hill related detail and anecdote was passed from one person to another, with Clem’s letters always being neatly written in small writing.  He built up a lasting friendship with Mark and David through a multitude of letters relating to European hills and all manner of British hill data. 

All correspondence I had from Clem is neatly filed and occasionally read, it is one of my lasting regrets that I never replied to his last letter that I received.  It was during one of these occasional letter readings that I came across two listings adjoined to a letter dated 4th May 2001, one was entitled ‘Suggested drop figures for your possibles list’, whilst the other was entitled ‘Alterations to Marilyn Listing (Ireland)’.  The latter was detailed, as ever, but three listings caught my eye, all are highlighted in red ink, with one of the highlighted parts referring to two hills. 

Two have ‘Promoted from SubMarilyn’ next to them in red ink with one of these also adjoined with another hill with ‘New Marilyns’ in blue ink next to them, whilst the third has ‘Demote to SubMarilyn’ next to it.


The hills Clem had highlighted with their detail from the list in the letter are:

ADD        54B        Cullenagh Mtn.        317m        map 60 at S 498895        drop 152m

ADD        54B        Cullahill Mtn.        c 313m        map 60 at S 379710        drop 151m

Both of these hills have ‘New Marilyns’ in blue ink against them.  With Cullenach Mountain having ‘Promoted from SubMarilyn in red ink against it, the other hills highlighted are:

56B        Croghan Hill        234m at N 481331        drop 142m

This hill has ‘Demote to SubMarilyn’ in red ink against it.  It is the next highlighted detail that is of particular interest:

ADD        48B        Corronoher        273m        map 65 at R 409 310          drop 150

Highlighted in red ink against this hill is ‘Promoted from SubMarilyn’.


The list of data received in Clem's letter dated 4th May 2001
All these alterations were acted upon in 1998 in The Angry Corrie 37: Jun-Jul 98 'The Hewitts and Marilyns of Ireland - an update'.  All except the alteration to Corronoher.

Clem had originally listed Corronoher as a SubMarilyn with 273m summit and c 145m drop, giving the col a height of 128m.  This latter figure seems rather high, especially so when you consider Clem has instructed an alteration based on a col height of 123m, giving 150m of drop.

There seems to be two possibilities why this specified alteration was never acted upon:

1 The alteration to the drop of Corronoher only came about after the 1998 Irish Marilyn update.  If this is so Clem seemingly didn’t recognise the 128m col height in his TACit Irish Marilyn listing as too high until after the 1998 Angry Corrie update.  If this is correct why didn’t the alteration appear in a later Angry Corrie?  Perhaps Clem didn’t notify Dave Hewitt as he was busy with other listings?

2 Clem re-considered the alteration and decided against it.

At least part of number 1 can be answered as this alteration did not come about prior to the updates in the 1998 Angry Corrie, as it did not appear in the infamous Scottish hillzine, and to my knowledge Clem only mentioned this update in the letter he sent me in 2001 as there seems to be no other mention of it in any other correspondence I have seen.

Much to ponder, and David as joint custodian Author of the Irish Marilyns needed to be consulted.  We debated the merits of Clem’s instruction and scrutinised the col contouring, I favoured c 150m of drop based on a col height of 123m, whilst David favoured around c 148m of drop based on an estimated col height of 125m.  Certainly without agreement we would not promote the hill.  We had to dig a little deeper and see if any other detail had been missed.

The first person to contact was Dave Hewitt, who confirmed that there had been no Irish Marilyn update in the Angry Corrie after those published in 1998, although Clem did occasionally send other bits of information to him.

At least with this confirmation from Dave Hewitt we could concentrate on other possibilities.  One being that Clem wanted an update but he either didn't forward the detail to Dave Hewitt, or decided after May 2001 that his col interpolation of 123m col height, giving c 150m drop was incorrect, both of these options seem a little odd as I can't think of any reason why Clem didn't forward the detail to Dave, as he had already proceeded with one update, he could have easily put a paragraph with this update in a future Angry Corrie.  I also think the second option is a little odd, as at this time Clem and I were exchanging all manner of hill related data (this brings back good memories, he is sadly missed) and I'm sure Clem would have sent the detail through to me if he had changed his mind in relation to the c 123m col height and the 150m drop.

I then suggested we should contact John Fitzgerald who operates a Trimble GeoXH 6000 with the results attained from this highly accurate piece of surveying equipment being fed in to MountainViews and the DoBIH.  Over the last few years John has surveyed extensively in Ireland and is re-writing the status of many a hill in some of the more acknowledged Irish hill lists through his perseverance and expertise.  Once contacted I even tried to bribe him with the offer of getting him a new bandana if he surveyed the col, he enthusiastically accepted the bribe and informed me he’d like one coloured black!

John Fitzgerald with the Trimble GeoXH 6000 on a hill in Snowdonia
We now waited for John to venture north from his heartland of Cork.  He did this a few days ago and sent the following email detailing his col survey:


I happened to be passing the col of Corronoher last week and spent an hour or so trying to work out where the col was likely to be.
It is most probably on the land enclosed in the triangle formed by 3 roads with the point you suggested, R438 334, being slightly east of the triangles centre.
The contours do not reflect the terrain and what you would assume from the map is a flat area is in reality like a series of small drumlins.
After a bit of pondering I took the following as the best guess being reflective of the general levels with the proviso that there may in fact be a lower point within the Drumlins. 
R44095 32955 – Height (=/- 0.1 accuracy) 122.015 meters, 333 measurements taken. 
So looks like you have a Marilyn?


When this email popped in to my inbox I wondered where I was going to get a bandana from!?!  I contacted John and thanked him for surveying the col and then informed David.  We discussed the survey result and as the OSI map indicates that the summit has a trig and is in conifer plantation, it seems only the col can be accurately surveyed, and so we accepted Corronoher as a new Irish Marilyn.

Thanks need to be expressed to John Fitzgerald for surveying the col on behalf of MountainViews with his Trimble GeoXH 6000. 

Thanks should also be expressed to Clem as he originated the Irish Marilyn list after being inspired to do so from the listings of Eric Yeaman and Alan Dawson.

It seems rather fitting that the evening David and I discussed the implication of John’s survey and accepted Corronoher in to the ranks of Irish Marilyns was Monday March 17th – St Patrick’s Day.  It is also rather fitting that after almost 13 years Clem’s final instruction for his Irish Marilyn list is being acted upon.

Tuesday, 18 March 2014

Mapping Mountains – Trimble Surveys – Bryniau Clwyd


18.03.14  Moel Ffagnallt (SJ 190 699)


Moel Ffagnallt (SJ 190 699)
Mark wanted to discover one or two ‘new’ P30’s and the first hill on his radar was a few miles outside of Mold near the small hamlets of Moel-y-crio (SJ 195 697) and Rhes-y-cae (SJ 189 707).

The hill is easily accessible from the road that goes between the small communities via a green track that makes its way up the south-eastern flank of the hill.  The forecast for the day was not brilliant as the fine weather of the last couple of weeks had now been replaced by westerly’s blowing in from the Atlantic.  Although the heavier rain of the day proved to be whilst driving from Welshpool to Mold.

Before venturing up to the summit we explored the area of the bwlch, the critical point seemed to be in someone’s back garden, thankfully we were both of the opinion that land at this point had been terra-formed and therefore could not be considered as ‘natural’.  This at least meant that the Trimble could be set up in a field.  But before doing this we visited the summit.

The high point of the hill proved to be a small slab of concrete that was embedded in the ground.  Again we considered this as unnatural and decided to place the Trimble next to it on flattened grass.  Ten minutes of data was collected as the sky to the west turned grey and the wind whipped across the top. 


The Trimble GeoXH 6000 on the summit of Moel Ffagnallt with Moel Fama in the background
Away to the south the Clwyd hills were on grand display with the Jubilee Tower atop Moel Fama (SJ 161 626) standing out on the horizon.  As the Trimble edged nearer its allocated ten minutes of data collection showers were breaking out around the hills.  Thankfully only a few spots fell our way so no wet deluge descended upon us.

Next stop was the bwlch and having decided that a manicured lawn was not appropriate as being considered as ‘natural’ ground I crept in to an adjacent field and placed the Trimble on the low point of the hill to hill traverse which proved to be near to a hedge.  Another ten minutes of data was collected before we went driving off to explore the critical bwlch of another prospective ‘new’ P30 that would have to await another surveying day.

Trimbles like the outdoors and fields.  Much safer than urban environments and pavements!



Survey Result:


Moel Ffagnallt

Summit Height:  288.5m (converted to OSGM15)

Summit Grid Reference:  SJ 18999 70001

Bwlch Height:  261.3m (converted to OSGM15)

Bwlch Grid Reference:  SJ 19347 69850

Drop:  27.2m (200m Sub-Twmpau status confirmed)

Dominance:  9.44%



For further details please consult the Trimble survey spreadsheet click {here}

Sunday, 16 March 2014

Basic Levelling Survey - Comparison Spreadsheet



Introduction

Between January 1998 – January 2009 I surveyed over 420 hills in Wales using a staff with a fixed spirit level to sight from one point to another.  This procedure was repeated from bwlch to summit until the hill’s drop value was ascertained.  The best description for such a method is a Basic Levelling Survey (BLS).  For an introduction to this surveying method please click {here}.

These basic levelling surveys promoted a number of hills including four to the Nuttalls list, 18 to the Deweys list and 24 to the list now known as Y Pedwarau.

Since September 2008 G&J Surveys, and from December 2013 Mapping Mountains, have had access to survey grade GPS / GNSS equipment that can produce accurate absolute height measurements.

Since September 2008 a number of hills that were promoted to the lists mentioned above through BLS have had their drop values accurately surveyed, either by the Leica 530, Leica GS15, Timble GeoXH 6000 or by level and staff.  To date (March 2014) this has resulted in two demotions of hills from the Deweys list, both originally promoted due a BLS: Iwerddon (SH 688 482) and Cerrig yr Ieirch (SH 758 425).  Another 13 hills have been confirmed as being a Nuttall, Dewey or Pedwar and a further 13 hills have had an accurate survey comparison to the original BLS.  In all there are 28 hills out of the 420 whose drop was attained by a BLS that have now been surveyed by either level and staff and / or GPS / GNSS receiver, as time progresses this figure will increase.

As there is now a comparison of the survey results between 28 hills a statistical analysis can be made to determine the level of uncertainty applied to the surveys conducted with the staff and fixed spirit level.  It is hoped that this statistical analysis will appear on the Mapping Mountains blog in the near future.  But for now the details of the hills surveyed by the basic levelling technique that have also been accurately surveyed appear in a spreadsheet.

To see the Basic Levelling Survey Comparison spreadsheet click {here}


The spreadsheet consists of the following:

Date Accurately Surveyed:  This is the date when each hill was surveyed either by GPS / GNSS receiver or by line survey.

Date (BLS):  This is the date of each basic levelling survey.

Name:  This is considered the most appropriate name of the hill.  Sometimes the name used does not correspond to current Ordnance Survey map spelling or the name may not appear on any map.  Where no appropriate name has been discovered for the hill from any source, the Pt. (for example; Pt. 688m) notation is used rather than making up a name that has no local or historical evidence of use.

Height (m):  This gives the map height in metres of the hill above Ordnance Datum Newlyn (ODN), often referred to as sea level.  Where a height is quoted to a decimal place it implies that the hill has been surveyed by GPS / GNSS receiver (these heights may not match current Ordnance Survey map heights).  Where a ‘c’ (contour) appears preceding the height it means there is no known spot height available.

1:50,000 Map: This column gives the number of the 1:50,000 Ordnance Survey Landranger map that the point surveyed appears on.

1:25,000 Map:    This column gives the number of the 1:25,000 Ordnance Survey Explorer map that the point surveyed appears on.

Grid Reference:  This is the six figure grid reference produced by the GPS / GNSS receiver for the point surveyed or for those hills that have only been accurately surveyed by a level and staff this will be from a hand-held GPS unit.

Drop (Basic Levelling Survey) (ft):  This column details the drop in imperial measurement attained from the BLS.  This value is the relative height of the hill; this is commonly referred to as ‘drop’, ‘prominence’ or ‘reascent’.  The drop is the height difference between the summit and bwlch connecting the hill to next higher ground along the watershed. 

Drop (Basic Levelling Survey) (m):  This column details the drop in metric measurement attained by the BLS.

Drop (spot heights on OS maps) (m):  This column details the hill’s drop if a spot height for both summit and bwlch appear on an Ordnance Survey map.  The appearance of a spot height does not mean that it is placed at the uppermost part of the hill or at the critical bwlch. 

Drop (Line Survey) (m):  This column details the drop value in metric attained from a line survey (if one has taken place).  This form of survey gives the most accurate method to determine the height gain from bwlch to summit. 

Drop (GPS / GNSS Receiver) (m):  This column details the drop value in metric attained from a survey conducted by the Leica 530, Leica GS15 or the Trimble GeoXH 6000 (if one has taken place).  

Leica Disto (m):  The Leica Disto A8 is capable of measuring distance and angle.  To date it has only been used on one hill; Castell y Gwynt (SH 654 581) that has also been surveyed by a BLS.  

Distance from Bwlch to Summit (m):  As the BLS is easier to conduct over shorter horizontal distances (less margin for error in vertical alignment), the distance between the bwlch and summit is important to document.  Distances quoted are approximate.

Status (surveyed for):  This gives the class of hill applied to each survey.  For now the details in the spreadsheet only apply to the class of Nuttall, Dewey and Pedwar. 

Comments:  The last column is used to document if the hill has had more than one BLS, or if the hill appears in the relevant list by another name when compared to the one deemed the most appropriate by the blog author and details of the GPS / GNSS receiver used for the survey is also given in this column.




To see the Basic Levelling Survey Comparison spreadsheet click {here}

Friday, 14 March 2014

Mapping Mountains - Hill Reclassifications – Y Pedwarau


Cefn Perfa (SO 173 579) - 400m Sub-Pedwar reclassified to Pedwar

There has been a reclassification of a 400m Sub-Pedwar to a Pedwar which has recently been confirmed by a line survey conducted by John Barnard and Myrddyn Phillips.  This survey was prompted by a basic levelling survey conducted in 2003 which gave the hill 97ft / 29.6m of drop.  Subsequently the hill has been surveyed using the Trimble GeoXH 6000 resulting in 30.04m of drop, and now it has been surveyed using the Leica GS15 and a second survey by the Trimble GeoXH 6000 resulting in 30.06m and 30.09m of drop respectively.  The line survey, which is the most accurate for ascertaining the drop value, determined that the hill has 30.06m of drop and therefore its reclassification to a Pedwar is confirmed.  Few 400m hills could have seen so much surveying activity paid to them!  
The hill is named Cefn Perfa (SO 173 579) and it is situated in the Fforest Glud range of hills and is positioned on the outskirts of Llanfihangel Nant Melan.

The hill will be added to the Y Pedwarau list in the 2nd edition that will hopefully be published by Europeaklist.  The list of Pedwar hills is also available from the Haroldstreet website.


The full details for the hill are:


Cardinal Hill:  Gwaun Ceste

Summit Height:  411.2m (converted to OSGM15)

Name:  Cefn Perfa

OS 1:50,000 map:  148

Summit Grid Reference:  SO 173 579

Drop:  30.1m (line survey)


Cefn Perfa (SO 173 579) has now been confirmed as a Pedwar

For details on the survey that reclassified this hill to Pedwar status please click {here}


Myrddyn Phillips and Aled Williams (March 2014)