Thursday, 3 December 2015

Y Trechol - The Dominant Hills of Wales - Ynys Môn


Hill Lists – Cymru / Wales

Y Trechol - The Dominant Hills of Wales

Introduction

To access Y Trechol - The Dominant Hills of Wales list please click {here}

Dinas Gynfor (SH 391 950) is situated in the Ynys Môn Group of hills and is listed as one of The Dominant Hills of Wales

Listings of hills in Britain have progressed since Sir Hugh Munro first compiled a list to the Scottish 3,000ft mountains that eponymously now bear his name of the Munros.  Since Sir Hugh’s list was first published in the 1891 Scottish Mountaineering Club Journal the concept of how to differentiate one hill from another has developed with this association now mainly relying upon what is referred to as prominence.  This term is also known as reascent and drop, with this being the height gain between summit and connecting bwlch to the higher parent peak via the watershed.

Although differentiating one hill from another mainly relies upon prominence, it is not the only tool used to do so, as such criterion as distance, and height and prominence combined have also been used.  But prominence is now the main criterion used to differentiate one hill from another.

The concept of prominence was first investigated by the early hill list authors such as Corbett and Moss who employed the use of a single ring contour in their listings.  This system for cataloguing hills relied upon maps of the day that were based on ring contours at 50ft intervals, therefore a hill may be included that had a 5ft prominence or less because it had a separate ring contour, this is an obvious failing in this system.

However, Corbett had initialised the concept of objective judgment in how to make this all important differentiation between one hill and another, whereas Munro relied upon subjective judgment when he differentiated between his Separate Mountains (Munros) and their Subsidiary Tops (Munro Tops).

This objective judgement took its next stage forward when Carr and Lister used a 100ft criterion to differentiate one hill from another in their book to ‘The Mountains of Snowdonia’ which was published in 1925 by John Lane The Bodley Head Limited of London.  This use of 100ft by Carr and Lister can be considered as the first objective height differentiation and therefore the first use of how we now view the term prominence.

Although, as mentioned previously, there have been other use of criterion to differentiate one hill from another, there is a definite line between how the use of prominence has evolved, this line can be viewed as a link, but this link does not have many connecting parts to it, and up until the Dominant listing that this Introduction details, that connecting part only involved one link, and that is Relative Height, and now the second connecting link of Dominance has been added.

The difference between Prominence and Relative Height can be summarised as the following, with the explanation of Dominance then following:


Prominence is applied to hills whose qualification also depends upon minimum height.


Relative Height is applied to hills whose qualification is just dependent upon a minimum prominence.


Dominance is applied to hills whose prominence equal or exceed half that of their absolute height.


For those that are not initiated with the intricacies of hill list criteria the above explanation can sometimes be a difficult concept to understand, but the essence being is that Prominence is used as part of a criteria in conjunction with another criterion which is usually Minimum Height, whereas Relative Height is normally used as a singular criterion that is not dependent upon any form of minimum height except for that stipulated for its relative height, whereas Dominance relies upon the relationship between the hill’s prominence and its absolute height and is part of a criteria in conjunction with another criterion which is Minimum Height.

The first use of what we now refer to as Relative Height in a published hill list was by Eric Yeaman in his ‘Handbook of the Scottish Hills’ which was published in 1989 by Wafaida.  However, the term Relative Height was coined by Alan Dawson for the Marilyns which were first published in ‘The Relative Hills of Britain’ book by Cicerone Press in 1992.

These two publications dispensed with the concept of Prominence with Eric Yeaman using 100m of Relative Height as the main part of his Scottish list and Alan Dawson using 150m for his British list.

The next link in this small chain that takes in Prominence and Relative Height is Dominance, and therefore Dominance can be viewed as the next step in the evolutionary process of Prominence.

Dominance is a new concept for a published list to hills within Britain and to the knowledge of the author was first used for hills within Britain in early 2009 under the working title of ‘The Ultra Prominent Summits of Wales’, this title was shortened to the UPPs and was later changed to ‘The Dominant Hills of Wales.’  The change of name was instigated after a discussion with Mark Trengove who pointed out that the same concept of Dominance had been used by Eberhard Jurgalski in written format in 2001 and in published format in 2004, and as the 5,000ft prominence world peaks are known as the Ultras, their title having been shortened from the Ultra Prominent Peaks, it was sensible not to use a working title that was similar to another list that used different criteria.  Therefore, the title of Y Trechol - The Dominant Hills of Wales became the norm and the term of Dominance used to describe it, with the term Y Trechol being the Welsh for ‘The Dominants.’

The concept of Dominance was independently conceived by the author and was not copied from Eberhard as until discussing the concept of this list with Mark Trengove, I had not heard of Eberhard Jurgalski, but the term ‘Dominance’ follows Eberhard’s lead, as this is the norm when dealing with terms such as Prominence and Relative Height, each in turn were coined by someone and then they have become terms used by many.

To fulfil the qualification of a hill being Dominant its prominence has to be first known.  Therefore a Dominant list cannot be compiled unless the Prominence of each hill is known beforehand, and for a country such as Wales there are many hills that qualify under a stipulated minimum prominence of 30m.  I thought it wise to follow this minimum prominence figure as this had been previously used in a number of listings, these are briefly detailed below.

For Wales these 30m minimum prominence based lists were first published over a period of 20 years from 1984–2004.  These listings were reliant upon data produced by Terry Marsh, Michael Dewey and Myrddyn Phillips.  However, although all the lists produced by these people specified a minimum drop of 30m none of them listed the actual drop figure; this was added at a later date.  During this time listings to the majority of these hills were also independently produced by E. D. ‘Clem’ Clements whose work appeared on the RHB Yahoo Group database.

The theory of Dominance was conceptualized shortly after all the drop values were added to my hand written Master Lists and the 100m height bands expanded upward to include all P30 summits in Wales.  This Dominance criterion was conceptualized at approximately the same time as that of Remoteness, with both taking form from the same question – ‘what else can be considered once prominence values are given to all hills?’  Once this question was asked the theory of Dominance sprung in to my mind and that of Remoteness soon followed.

The Remoteness list was later published on Geoff Crowder’s v-g.me website in 2011, and updated and co-authored with Aled Williams and published by Europeaklist, Haroldstreet and Mapping Mountains in April 2015.  But until now the Dominance list has never been published.


Before detailing what Y Trechol - The Dominant Hills of Wales list consists of it may be prudent to detail the qualification for the main list:

Those P30 hills whose prominence equal or exceed half that of their absolute height.

Also included is a list to the Lesser Welsh Dominants, these are the additional P30 summits whose prominence is between one third and half that of their absolute height.



To access Y Trechol - The Dominant Hills of Wales list please click {here}



The list consists of the following:

Group:  Each hill appears under their Group, this is the group / range that the hill is a part of.  For example; Carnedd Llywelyn (SH 683 643) is part of the hill group known as the Carneddau.  The Groups are arranged from north to south on a west to east orientation.  The names of the Groups used in this list have received extensive input from Aled Williams.

Name:  This is considered the most appropriate name for the hill with respect to the information available to the author.  Sometimes the name used does not correspond to current Ordnance Survey map spelling and composition or the name may not appear on any map.  Where no appropriate name has been discovered for the hill from any source, the Point (for example; Pt. 78m) notation is used rather than making up a name that has no local or historical evidence of use.  The Welsh place-names that appear in this list and that were sourced from Ordnance Survey mapping are reproduced as simple compositions, with hyphenated and compound names reduced to the component elements.  It must be noted that this process will on occasion result in loss of pronunciation information and as such, is not ideal.  However, this protocol has been implemented in order to simplify the composition due to the inappropriate and inconsistent hyphen use that Ordnance Survey maps are prone to.

Dominance:  This is the Dominance of the hill’s height between bwlch and summit (its prominence) over that of its height from sea level (Ordnance Datum Newlyn) to its bwlch.  The Dominance is given as a percentage.

Region:  There are three Regions in Wales; North Wales, Mid and West Wales, and South Wales.  The Regional split of Wales used in this list has received extensive input from Aled Williams and will be detailed on the Mapping Mountains blog at a later date.

Sub-Region:  There are a number of Sub-Regions in Wales and those used in this list have received extensive input from Aled Williams and they will be detailed on the Mapping Mountains blog at a later date.

1:50,000 Map:  This column gives the number or numbers of the 1:50,000 Ordnance Survey Landranger map that the summit of the hill appears on.

1:25,000 Map:  This column gives the number or numbers of the 1:25,000 Ordnance Survey Explorer map that the summit of the hill appears on.

Grid Reference Summit:  This is the ten figure grid reference (10FGR) for the summit of the hill.  This has either been produced by an accurate survey, a map spot height or when neither is available by a centralised position in an uppermost contour ring.  When the accurate survey has been conducted independent of the Ordnance Survey a (S) for ‘survey’ will appear adjacent to the 10FGR, a (TP) if the 10FGR is taken to a ‘trig pillar’, a (B) if the 10FGR is taken to a ‘bolt’ or a ‘block’, a (L) if the 10FGR is taken to the position of a ‘levelled’ height on old maps, a (HH) if the 10FGR is taken from a ‘hand-held’ GPS unit, a (SH) if the 10FGR is taken to a ‘spot height’ either on current or old maps and an (I) if the summit position has been ‘interpolated’ from contours.

Height (m) Summit:  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’ (circa) appears preceding the height it means there is no known spot height available and the height has been estimated from contour interpolation.

Grid Reference Bwlch:  This is the ten figure grid reference (10FGR) for the bwlch of the hill.  This has either been produced by an accurate survey, a map spot height or when neither is available by a centralised position between converging hill to hill and valley to valley contours.  When the accurate survey has been conducted independent of the Ordnance Survey a (S) for ‘survey’ will appear adjacent to the 10FGR, a (L) if the 10FGR is taken to the position of a ‘levelled’ height on old maps, a (HH) if the 10FGR is taken from a ‘hand-held’ GPS unit, a (SH) is the 10FGR is taken to a ‘spot height’ either on current or old maps and an (I) if the bwlch position has been ‘interpolated’ from contours.

Drop (m) Summit to Bwlch:  This column details the prominence of the hill; this is commonly referred to as ‘drop’ or ‘reascent’.  The drop is the height difference between the summit and connecting bwlch to the higher parent peak along the watershed.  The letter ‘c’ before the drop figure signifies there is no spot height or surveyed height known for either summit or more usually, the bwlch, therefore a part of the drop figure has been estimated from contour interpolation.

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

Notes:  This column gives details relevant to the hill.


With special thanks to Aled Williams and Mark Trengove for their continued support and to Eberhard Jurgalski for taking Dominance to the masses.  Thanks are also due to the people who submit 10 figure grid references to the Database of British and Irish Hills (DoBIH) and for DoBIH making these available for public use.


This list will appear in biweekly or monthly instalments with the first Group listed being Ynys Môn.  The Dominant Hills of the Carneddau will appear on the 17th December 2015.

To access Y Trechol - The Dominant Hills of Wales list please click {here}






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