Change Register - Y Trechol - The Dominant Hills of Wales

Change Register

Y Trechol – The Dominant Hills of Wales

Y Trechol  – The Dominant Hills of Wales are the Welsh P30 hills whose prominence equal or exceed half that of their absolute height, with the minimum qualifying mark given as a percentage (50%).  The list was conceptualized after adding drop values to the hand written Master Lists that took in the P30 hills of Wales that were published on Geoff Crowder’s v-g.me website, this was during 2006 and 2007 and the compilation of what was to become Y Trechol – The Dominant Hills of Wales followed soon afterward.

The original title for the list was the UPP’s, an abbreviation for the Ultra Prominent Peaks of Wales; this title was later changed to The Dominant Hills of Wales.  The change of name was instigated after a discussion with Mark Trengove who informed me that the same concept of Dominance had been used by Eberhard Jurgalski in written format in 2001 and in published format in 2004.  I also realised that the original title could be confused with the listing of 5,000ft prominence world peaks that are known as the Ultras, their title having been shortened from the Ultra Prominent Peaks, as it was sensible not to use a working title that was similar to another that used different criteria I opted for the title of Y Trechol - The Dominant Hills of Wales, with the term of Dominance used to describe it, and the words Y Trechol being the Welsh for The Dominants.  Accompanying the main list is a sub list entitled The Lesser Dominant Hills of Wales, these are the additional P30 Welsh hills whose prominence is 33% or more and below 50% of their absolute height.

Although Y Trechol – The Dominant Hills of Wales was originally compiled in 2006 – 2007 after drop values were added to the Welsh P30 lists, the listing did not commence publication until 3^rd December 2015, with ‘commence’ being the operative word as this is ongoing with bi-weekly, monthly, bi-monthly or quarterly instalments of hill groups being published on Mapping Mountains.

Although the criteria has remained the same in the Dominant and Lesser Dominant list, the listing has benefited greatly since its first compilation with the advent of independent surveyors using GPS / GNSS receivers,  the analysis of LIDAR data and the availability of an expanded range of online Ordnance Survey maps all adding greater accuracy to the numerical data.  However, it is not just numerical data that has seen this list develop since its first inception, as local enquiry and historical research are enhancing the place-name data used for the listed hill names.

It seems fitting that the list of Y Trechol – The Dominant Hills of Wales should now benefit from a detailed Change Register, and although the changes to this list have been catalogued on the Mapping Mountains site it will be useful to list all status changes to the list since first compilation and present them in a Change Register.

The Change Register to Y Trechol – The Dominant Hills of Wales appears below with the reclassifications to the Dominant list being detailed chronologically in receding order.

Change Register

Y Trechol – The Dominant Hills of Wales

Carreg Rhoson    28m at SM 67228 25658 

Carreg Rhoson (SM 672 256) is the island on the right of this photo

This hill was deleted from Dominant status on the 22.03.24, with it previously listed as a Dominant hill with 100.00% dominance due to a small uppermost 30m ring contour on the Ordnance Survey 1:25,000 Explorer map.  Its deletion is due to detail on the DataMapWales with a 28m spot height appearing on this mapping.  Dominant total decreases by one and confirmed as 268.

The Rookery    102.6m at SN 61191 22707

LIDAR image of The Rookery (SN 611 227)

The reclassification of this hill to Dominant status was announced when the Hill Reclassifications post was published on Mapping Mountains on the 20.04.22.  The hill was previously listed with an estimated c 49m of drop and 48.04% dominance, based on the 102m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 53m bwlch height based on interpolation of 10m contouring between 50m – 60m.  Its reclassification to Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips, resulting in a 102.6m summit height and a 50.3m bwlch height, with these values giving this hill 52.2m drop and 50.94% dominance.  Dominant total increases by one and confirmed as 269.

Dinas Fach    30.45m at SM 82559 22659 

LIDAR image of Dinas Fach (SM 825 226)

The addition of this hill to Dominant status was incorporated in to the list on the 09.12.20 and announced when the Hill Reclassifications post was published on Mapping Mountains on the 17.10.21.  The hill was previously not classified due to inconsistency between contours on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.  Its addition to Dominant status is due to Joe Nuttall who produced a summit analysis programme using LIDAR, and then by LIDAR analysis initially conducted by Jim Bloomer and subsequently by Myrddyn Phillips, resulting in a 30.45m summit height and a 0.3m bwlch height, with these values giving this hill 30.15m of drop and 99.01% dominance.  Dominant total increases by one and confirmed as 268.

Ynys Dafydd    52.8m at SH 64636 17484 

LIDAR image of Ynys Dafydd (SH 646 174)

The addition of this hill to Dominant status was announced when the Hill Reclassifications post was published on Mapping Mountains on the 07.09.21.  The hill was previously listed with an estimated c 27m of drop based on an estimated c 42m summit height and an estimated c 15m bwlch height, with both values based on interpolation of 10m contouring that appears on the Ordnance Survey 1:25,000 Explorer map.  Its addition to Dominant status is due to Joe Nuttall who produced a summit analysis programme using LIDAR, and then by LIDAR analysis initially conducted by Jim Bloomer and subsequently by Myrddyn Phillips, resulting in a 52.8m summit height and a 17.1m bwlch height, with these values giving this hill 35.7m of drop and 67.61% dominance.  Dominant total increases by one and confirmed as 267.

The Park    85.6m at SN 66441 93678 

LIDAR image of The Park (SN 664 936) 

The reclassification of this hill to Dominant status was announced when the Hill Reclassifications post was published on Mapping Mountains on the 28.07.21.  The hill was previously listed with an estimated c 41m of drop and 49.40% dominance, based on an estimated c 83m summit height and the 42m bwlch spot height that appears on the Ordnance Survey 1:25,000 Explorer map.  Its reclassification to Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips, resulting in an 85.6m summit height and a 42.7m bwlch height, with these values giving this hill 42.9m drop and 50.09% dominance.  Dominant total increases by one and confirmed as 266.

Ynys Fach    43.5m at SN 66845 95141

LIDAR image of Ynys Fach (SN 668 951)

This hill’s addition to Dominant status was announced when the Hill Reclassifications post was published on Mapping Mountains on the 26.03.21.  The hill was previously listed with an estimated c 27m of drop based on an estimated c 34m summit height and an estimated c 7m bwlch height, with both values based on interpolation of 10m contouring that appears on the Ordnance Survey 1:25,000 Explorer map.  Its addition to Dominant status is due to Joe Nuttall who produced a summit analysis programme using LIDAR, and then by LIDAR analysis initially conducted by Jim Bloomer and subsequently by Myrddyn Phillips resulting in a 43.5m summit height and a 2.1m bwlch height, with these values giving this hill 41.3m of drop and 95.10% dominance.  Dominant total increases by one and confirmed as 265.

Glan y Morfa    59.2m at SH 43819 67923 

LIDAR image of Glan y Morfa (SH 438 679)

This hill’s addition to Dominant status was announced when the Hill Reclassifications post was published on Mapping Mountains on the 10.03.21.  The hill was previously listed with 27m of drop based on twin tops both with a 59m summit spot height (59m at SH 43811 67899 on the Ordnance Survey 1:25,000 Explorer map and 59m at SH 45087 68972 on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map) and a bwlch height of 32m that appears as a spot height on the Ordnance Survey 1:25,000 Explorer map.  Its addition to Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips resulting in a 59.2m summit height and a 27.9m bwlch height, with these values giving this hill 31.3m of drop and 52.85% dominance, with the bwlch height taken to a railway cutting.  Dominant total increases by one and confirmed as 264.

Pen y Foel    122.5m at SH 42575 84415 

The Trimble GeoXH 6000 gathering data at the summit of Pen y Foel (SH 425 844)

This hill’s reclassification to Dominant status was announced when the Hill Reclassifications post was published on Mapping Mountains on the 04.03.21.  The hill was previously listed with 49.40% dominance based on the 122.5m summit height derived from a Trimble GeoXH 6000 survey and a 62m bwlch height based on the spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map.  Its reclassification to Dominant status is due to partial LIDAR coverage of its bwlch, resulting in a more accurate interpolation of its bwlch height to an estimated c 61m, with these values giving this hill an estimated c 62m of drop and 50.21% dominance.  Dominant total increases by one and confirmed as 263.

Wilcrick Hill    69.8m at ST 41128 87829

LIDAR image of Wilcrick Hill (ST 411 878)

This hill’s reclassification to Dominant status was announced when the Gwent Is Coed group of hills was published on Mapping Mountains on the 03.07.19, with a subsequent Hill Reclassifications post being published on Mapping Mountains on the 10.09.20.  The hill was originally listed with 49.28% dominance based on the 69m summit and 35m bwlch spot heights that appear on the Ordnance Survey 1:25,000 Explorer map.  However, as the 35m spot height appears between 30m – 35m contouring the drop value for this hill was re-assessed, resulting in an estimated c 33m bwlch height being used, giving c 36m of drop and 52.17% dominance.  The confirmation of its reclassification to a Dominant hill is due to LIDAR analysis conducted by Myrddyn Phillips, resulting in a 69.8m summit height and a 33.3m bwlch height, with these values giving this hill 36.4m of drop and 52.21% dominance.  Dominant total increases by one and confirmed as 262.

Cae Rosser    72.7m at SO 38857 00521

LIDAR image of Cae Rosser (SO 388 005)

This hill’s reclassification to Dominant status was announced when the Gwent Is Coed group of hills was published on Mapping Mountains on the 03.07.19, with a subsequent Hill Reclassifications post being published on Mapping Mountains on the 21.07.20.  The hill was originally listed with 49.32% dominance based on a 73m summit height and an estimated c 37m bwlch height, with these values giving this hill c 36m of drop.  Its reclassification to a Dominant hill is due to LIDAR analysis conducted by Myrddyn Phillips, resulting in a 72.7m summit height and a 32.2m bwlch height, with these values giving this hill 40.5m of drop and 55.68% dominance.  Dominant total increases by one and confirmed as 261.

Trostrey Hill    199.3m at SO 36920 05188

LIDAR image of Trostrey Hill (SO 369 051)

The reclassification of this hill from Dominant status was announced when the Mynyddoedd Duon group was published on Mapping Mountains on the 03.07.19, with a subsequent Hill Reclassifications post being published on Mapping Mountains on the 12.03.20.  The hill was originally listed with 68.84% dominance based on a 199m summit height and a 62m bwlch height, with these values giving this hill 137m of drop.  Its reclassification to Lesser Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips, resulting in this hill being lower than the adjacent hill of Coed y Bwnydd (SO 36613 06919) and therefore their bylchau swapped.  LIDAR analysis gives this hill a 199.3m summit height and a 129.1m bwlch height, with the former taken to remaining natural ground with LIDAR also giving a 199.5m height positioned at SO 36920 05184 to a raised field boundary that is excluded from the height of this hill as it is considered a relatively recent man-made construct, with these values giving this hill 70.2m of drop and 35.23% dominance.  Dominant total decreases by one and confirmed as 260.

Coed y Bwnydd    201.4m at SO 36613 06919

LIDAR image of Coed y Bwnydd (SO 366 069)

The reclassification of this hill to Dominant status was announced when the Mynyddoedd Duon group was published on Mapping Mountains on the 03.07.19, with a subsequent Hill Reclassifications post being published on Mapping Mountains on the 01.02.20.  The hill was originally listed with 34.69% dominance based on a 196m summit height and an estimated c 128m bwlch height, with these values giving this hill c 68m of drop.  Its reclassification to Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips, resulting in this hill being higher than the adjacent Trostrey Hill (SO 36920 05188) and therefore their bylchau swapped.  LIDAR analysis gives this hill a 201.4m summit height and a 59.4m bwlch height, with the former taken to an earthen embankment that forms a part of an ancient hill fort and the latter taken to a road cutting, both of which conform with the criteria used within this list, with these values giving this hill 142.0m of drop and 70.50% dominance.  Dominant total increases by one and confirmed as 261.

Ash Wood    206.4m at SO 48011 12229

LIDAR image of Ash Wood (SO 480 122)

This hill’s reclassification to Dominant status was announced when the Mynyddoedd Duon group was published on Mapping Mountains on the 03.07.19, with a subsequent Hill Reclassifications post being published on Mapping Mountains on the 22.01.20.  The hill was originally listed with 49.03% dominance based on an estimated c 206m summit height and an estimated c 105m bwlch height, with these values giving this hill c 101m of drop.  Its reclassification to a Dominant hill is due to LIDAR analysis conducted by Myrddyn Phillips, resulting in a 206.4m summit height and a 97.6m bwlch height, with the latter taken to a track cutting which conforms with the criteria used within this list, with these values giving this hill 108.8m of drop and 52.69% dominance.  Dominant total increases by one and confirmed as 260.

Dinas Powys    69.4m at ST 14823 72225

LIDAR image of Dinas Powys (ST 148 722)

The addition of this hill to Dominant status was announced when the Bro Morgannwg group was published on Mapping Mountains on the 03.06.19, with a subsequent Hill Reclassifications post being published on Mapping Mountains on the 10.11.19.  The hill was not included in the original 30-99m height band of Welsh P30 hills and its addition as a Dominant hill was confirmed by LIDAR analysis conducted by Myrddyn Phillips, resulting in a 69.4m summit height and a 33.6m bwlch height, with these values giving this hill 35.8m of drop and 51.57% dominance.  Dominant total increases by one and confirmed as 259.

Ash Tip    50.0m at ST 03170 66338

LIDAR image of Ash Tip (ST 031 663)

This hill’s addition to Dominant status was announced when the Bro Morgannwg group was published on Mapping Mountains on the 03.06.19, with a subsequent Hill Reclassifications post being published on Mapping Mountains on the 27.10.19.  The hill was not included in the original 30-99m height band of Welsh P30 hills as there were no contours of note taking in what is now a man-made hill on contemporary Ordnance Survey maps of the day.  Its addition as a Dominant hill was confirmed by LIDAR analysis conducted by Myrddyn Phillips, resulting in a 50.0m summit height and a 12.4m bwlch height, with these values giving this hill 37.6m of drop and 75.20% dominance.  Dominant total increases by one and confirmed as 258.

Pt. 65.9m    65.9m at ST 35225 94717

LIDAR image of Pt. 65.9m (ST 352 947)

The reclassification of this hill to Lesser Dominant status was announced when the Cymoedd Gwent group of hills was published on Mapping Mountains on the 03.05.19, with a subsequent Hill Reclassifications post being published on Mapping Mountains on the 14.09.19.  The hill was originally listed with 50.00% dominance based on the 66m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 33m bwlch spot height that appears on the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map.  The reclassification of this hill is due to LIDAR analysis conducted by Myrddyn Phillips resulting in a 65.9m summit height and a 34.3m bwlch height, with these values giving this hill 31.6m of drop and 47.93% dominance.  Dominant total decreases by one and confirmed as 257.

Mynydd Machen    363.2m at ST 22381 90013

LIDAR image of Mynydd Machen (ST 223 900)

This hill was excluded when the Cymoedd Gwent group was published on Mapping Mountains on the 03.05.19, with a subsequent Hill Reclassifications post being published on Mapping Mountains on the 18.07.19.  The hill was originally listed with 53.31% dominance based on the 362m summit spot height and an estimated bwlch height of c 169m, with these values giving this hill c 193m of drop.  The status of this hill was re-assessed as the Ordnance Survey Vector Map gave a 375m summit spot height to Mynydd y Grug (ST 177 906); an adjoining and connected hill.  The latter summit height is the product of mine spoil and as the summit is considered solid and stable the respective bylchau for each hill was swapped resulting in the drop of Mynydd Machen decreasing.  The confirmation of this hill’s deletion from Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips resulting in a 363.2m summit height and a 250.6m bwlch height, with these values giving this hill 112.7m of drop and 31.01% dominance.  Dominant total decreases by one and confirmed as 258.

Warren Hill    44.5m at SS 73667 94066

LIDAR image of Warren Hill (SS 736 940)

This hill’s addition to Dominant status was announced when the Cymoedd Morgannwg group was published on Mapping Mountains on the 03.04.19, with a subsequent Hill Reclassifications post being published on MappingMountains on the 24.06.19.  The hill was not included in the original 30-99m height band of Welsh P30 hills, which was an oversight on my part as it met the criteria then used for the sub list.  However, it was included as a P30 based on detail from the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map.  Its addition as a Dominant hill was confirmed by LIDAR analysis conducted by Myrddyn Phillips, resulting in a 44.5m summit height and a 13.2m bwlch height, with these values giving this hill 31.3m of drop and 70.35% dominance.  Dominant total increases by one and confirmed as 259.

Mynydd y Glyn    377m at ST 03193 89647

This hill’s status as a Dominant hill was announced when the Cymoedd Morgannwg group was published on Mapping Mountains on the 03.04.19, with a subsequent Hill Reclassifications post being published on Mapping Mountains on the 14.05.19.  The hill was originally listed with 48.28% dominance based on the 377m summit spot height and an estimated bwlch height of c 195m, with these values giving this hill c 182m of drop.  The reclassification of this hill is due to LIDAR bwlch analysis conducted by Myrddyn Phillips resulting in a bwlch height of 187.7m, which when coupled with its 377m summit height gives this hill 189m of drop and 50.20% dominance.  Dominant total increases by one and confirmed as 258.

Bryn    36.7m at SH 42656 36173

LIDAR summit image of Bryn

This hill’s addition to Dominant status was accepted shortly after Chris Pearson suggested the hill as a P30 initialising LIDAR analysis conducted by Chris Crocker which confirmed its status, with a retrospective Hill Reclassifications post being published on Mapping Mountains on the 05.02.19.  The hill was originally listed with an estimated c 28m of drop, which was amended to c 29m of drop when the Ordnance Survey Interactive Coverage Map became available online via the Geograph website.  It was subsequently analysed by LIDAR and surveyed using the Trimble GeoXH 6000 by Myrddyn Phillips, with the former showing that this hill is not a natural P30 and only now accepted as one as a railway cutting has destroyed the natural bwlch and reduced its height and therefore increased the drop value of this hill.  The confirmation of this hill’s addition to Dominant status is due to a Trimble GeoXH 6000 summit survey and LIDAR analysis of its bwlch, resulting in a 36.7m summit height and a 6.6m bwlch height, with these values giving this hill 30.0m of drop and 81.88% dominance.  Dominant total increases by one and confirmed as 257.

Cae Ffwyn Uchaf    66.6m at SN 58825 00532

LIDAR image of Cae Ffwyn Uchaf

This hill’s reclassification from Dominant to Lesser Dominant status was announced when the Mynydd Penlle’rcastell group of hills were published on Mapping Mountains on the 03.12.18, with a Hill Reclassifications post being published on the 04.02.19.  The hill was initially classified as a Dominant based on a 67m summit spot height and an estimated bwlch height of c 33m, with these values giving this hill c 34m of drop and 50.75% dominance.  This hill’s reclassification to Lesser Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips resulting in a 66.6m summit height and a 36.0m bwlch height, giving this hill 30.6m of drop and 45.90% dominance.  Dominant total decreases by one and confirmed as 256.

Hidden Slabs Stack    6.5m at SS 11902 98247

This hill was not included as a Dominant hill when the Brandy Hill group of hills was published on Mapping Mountains on the 03.09.18, and a Hill Reclassifications post was then published on the 06.10.18.  The hill was listed as a Dominant based on information received from Dave Viggers who is now one of the Vice Presidents of the Climber’s Club, the approximate height had been given as c 30m, but site visits by a number of people including Jon Glew, Douglas Law, Rob Woodall and Adrian Rayner brought in to doubt the existence of a prominent sea stack at this position.  The confirmation of this hill’s deletion from Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips resulting in a 6.5m summit height, and with the same drop value this hill does not have sufficient prominence to be considered for Dominant status.  Dominant total decreases by one and confirmed as 257.

No Name Stack    31.1m at SR 97567 93273

This hill was not included as a Dominant hill when the Brandy Hill group of hills was published on MappingMountains on the 03.09.18, and a Hill Reclassifications post was then published on the 30.09.18.  The hill was listed as a Dominant based on information received from Dave Viggers who is now one of the Vice Presidents of the Climber’s Club, the approximate height was then revised based on the 30m spot height that appears on Ordnance Survey 1:25,000 Explorer maps, however this hill is adjoined to the mainland and is not tidal which meant that its P30 status was always debatable.  This hill’s deletion from Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips resulting in a 31.1m summit height of a 2.6m bwlch height, with these values giving this hill 28.5m of drop, which is insufficient for Dominant status.  Dominant total decreases by one and confirmed as 258.

Pen Twmp    217m at SM 98820 32984

This hill’s reclassification from Lesser Dominant to Dominant status was announced when the Mynydd Preseli group of hills were published on Mapping Mountains on the 03.07.18, with a Hill Reclassifications post being published on the 14.08.18.  The hill was initially classified as a Dominant based on interpolation of bwlch contours and later reclassified to a Lesser Dominant (see below) based on the 109m spot height that appears on the area of this hill’s bwlch on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website.  This hill’s reclassification back to Dominant status is due to LIDAR bwlch analysis conducted by Myrddyn Phillips resulting in a bwlch height of 108.3m, giving this hill 109m of drop and 50.09% Dominance.  Dominant total increases by one and confirmed as 259.

Fegla Fach    31.5m at SH 63818 15311

Fegla Fach (SH 638 153) is now listed as a Dominant hill

The addition of this hill to Dominant status was announced on Mapping Mountains on the 25.07.18 when the Hill Reclassification post was published, however its addition as a 30-99m Twmpau and it having 30m of drop had been announced on Mapping Mountains on the 05.07.18.  Prior to LIDAR analysis, an on-site visit and a survey with the Trimble GeoXH 6000 this hill was listed with 25m of drop based on the 28m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 3m spot height that appears on the area of this hill’s bwlch on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website.  The summit height produced by 1m DTM LIDAR analysis is 31.5m, however as the high point of this hill consists of a large rock it is likely that the LIDAR technique did not model the very highest part of this rock, whilst the bwlch height produced by the Trimble GeoXH 6000 survey is 1.5m, with these values giving this hill 30.0m of drop and 95.37% Dominance.  Dominant total increases by one and confirmed as 258.

Ynys Ddu    31.9m at SM 88673 38869

The announcement of this hill’s addition to Dominant status was made on Mapping Mountains when the Mynydd Preseli group of hills were published on the 03.07.18, with a Hill Reclassification post being published on the 04.08.18.  This hill’s status as a P30 was brought to the attention of the hill bagging community by Mick Moore, and prior to LIDAR analysis, this hill was listed with an estimated c 32m summit height based on the small 30m uppermost contour ring on Ordnance Survey 1:25,000 Explorer maps.  The summit height produced by 2m DSM LIDAR analysis is 31.9m and the bwlch height is 0.5m, with these values giving this hill 31.3m of drop and 98.28% Dominance which is sufficient for Dominant status.  Dominant total increases by one and confirmed as 257.

Rhos Ymryson    324m at SN 46038 50017

The Lesser Dominant status of this hill was announced on Mapping Mountains on the 03.06.18 when the Rhos Ymryson group of hills was published, with a Hill Reclassification post appearing on Mapping Mountains on the 04.06.18.  The hill was previously listed as a Dominant hill with 50.15% dominance based on the 327m summit and 163m bwlch spot heights that appear on the Ordnance Survey 1:25,000 Explorer map.  However, as this summit height is given to the top of a covered reservoir, and as these constructions are not accepted as being a part of a hill’s height in this list, the summit height was re-evaluated.  As the position of the highest natural ground at the base of the covered reservoir is given as SN 46038 50017 and as this is extremely close to where a 1062ft (323.7m) levelled height appears on the Ordnance Survey series of Six-Inch maps which matches the rounded up 324m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger map, it is this height that is being used for that of this hill’s summit, and when coupled with the 162.5m bwlch height derived from LIDAR analysis, these values give this hill 161m of drop and 49.83% dominance which is insufficient for its continued status as a Dominant hill.  Dominant total decreases by one and confirmed as 256.

Bryn y Gwynt    58.2m at SH 59949 44915

The addition of this hill to Dominant status was announced on the Mapping Mountains site on the 30.01.18, the hill was previously listed with c 29m of drop based on the 56m spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 27m based on 10m contour intervals between 20m – 30m.  This hill’s addition is due to analysis conducted by Aled Williams of data produced via LIDAR resulting in a 58.2m summit height and a 28.0m bwlch height, with these values giving this hill 30.2m of drop and 51.89% Dominance.  Dominant total increases by one and confirmed as 257.

Carn Ysgubor    102.4m at SM 69953 24603 

Carn Ysgubor (SM 699 246) has now been reclassified back into the ranks of Lesser Dominant hills

This hill was originally listed as a Lesser Dominant and subsequently reclassified to a Dominant hill based on the result of a survey conducted with the Trimble GeoXH 6000 (see below), the adoption of OSGM15 has resulted in accurately known heights in Wales increasing by approximately 2-4cm and this has resulted in Carn Ysgubor being reclassified back to Lesser Dominant status.  The announcement of this hill’s reclassification back to a Lesser Dominant hill was made on the Mapping Mountains site on 05.07.17, the hill was previously listed with 50.00% Dominance based on the 102.4m summit and 51.2m bwlch heights produced by a survey with the Trimble GeoXH 6000 conducted by Myrddyn Phillips on the 15.05.16, these values when converted to OSGM15 are 102.395m summit and 51.208m bwlch heights, with these values giving 51.187m drop and 49.99% Dominance.  Dominant total decreases by one and confirmed as 256.

Carn Ysgubor    102.4m at SM 69953 24603 

Prior to OSGM15 conversion the Trimble GeoXH 6000 survey of Carn Ysgubor (SM 699 246) reclassified it from a Lesser Dominant to a Dominant hill

The announcement of this hill’s reclassification from a Lesser Dominant to a Dominant hill was made on the Mapping Mountains site on 09.06.16 with the Hill Reclassifications post being published on the 10.06.16, the hill was previously listed with 49.50% Dominance based on the 101m summit spot height on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 51m based on interpolation of  bwlch contouring between 50m – 55m, with these values giving this hill c 50m of drop.  This hill was subsequently surveyed with the Trimble GeoXH 6000 by Myrddyn Phillips on 15.05.16, resulting in the summit height being 102.4m and the bwlch height being 51.2m, giving a drop value of 51.2m and a Dominance value of 50.00%.  The survey data for this hill has subsequently been converted to OSGM15 resulting in the hill being reclassified back to Lesser Dominant status (see above).  Dominant total increases by one and confirmed as 257.

Cefn    118.2m at SH 72126 00402 

Cefn (SH 721 004)

The details relating to this hill were re-evaluated on the 06.06.16, resulting in it being reclassified from a Lesser Dominant to a Dominant hill, with this being announced on Mapping Mountains on the 03.12.16 when the Tarren y Gesail group of hills were published, with a retrospective Hill Reclassifications post published on Mapping Mountains on the 28.05.17.  The hill was previously listed with 48.25% dominance based on an estimated c 114m summit height taken from interpolation of its uppermost 110m ring contour, and the 59m bwlch spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.  Its reclassification is due to the 119m summit spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map and when coupled with the 59m bwlch spot height, these values gave this hill 50.42% dominance.  Its reclassification has subsequently been confirmed by LIDAR analysis conducted by Myrddyn Phillips, resulting in a 118.2m summit height and a 59.0m bwlch height, with these values giving this hill 59.2m of drop and 50.08% dominance.  Dominant total increases by one and confirmed as 256.

Ynys Fach    30.8m at SM 82209 32743 

Ynys Fach (SM 822 327) a marvelous hill whatever its Dominance

The deletion of this hill from Dominant status was announced on Mapping Mountains on the 06.06.16, with the survey that resulted in this hill’s deletion being conducted on the 14.05.16, and the Hill Reclassifications post being published on Mapping Mountains on the 08.06.16, the hill was previously listed with 100.00% Dominance based on an estimated c 31m summit height and the same drop value.  The hill has subsequently been surveyed using a Trimble GeoXH 6000 by Myrddyn Phillips, resulting in a 30.8m (converted to OSGM15) summit height and a 1.2m (converted to OSGM15) bwlch height, with these values giving this hill 29.6m of drop, which is insufficient for it to be considered for Dominant status.  Dominant total decreases by one and confirmed as 255.

Moelfre    74.1m at SH 55830 37553 

Moelfre (SH 558 375) is now reclassified from a Dominant to a Lesser Dominant hill

The announcement of this hill’s reclassification from a Dominant to a Lesser Dominant was made on the Mapping Mountains site on 03.03.16 with the Hill Reclassifications post being published on the 04.03.16, the hill was previously listed with 50.00% Dominance based on the 74m summit spot height on the Ordnance Survey enlarged mapping hosted on the Geograph website and an estimated bwlch height of c 37m based on bwlch contouring between 35m – 40m.  This hill was subsequently surveyed with the Trimble GeoXH 6000 by Myrddyn Phillips on 23.02.16, resulting in the summit height being 74.1m (converted to OSGM15) and the bwlch height being 37.8m (converted to OSGM15), giving a drop value of 36.3m and a Dominance of only 49.00%, which is insufficient for it to retain its Dominant status.  Dominant total decreases by one and confirmed as 256.

Pt. 66m    66m at SH 29957 27041 

This hill’s reclassification to a Dominant hill was announced on the 11.02.16 when the Pen Llŷn group of hills was published on Mapping Mountains, with a retrospective Hill Reclassifications post appearing on Mapping Mountains on 19.03.17, the hill was previously listed with 48.44% Dominance based on a 64m map heighted summit at SH 295 266.  In recent times the Ordnance Survey larger scaled mapping has become available on the Geograph website and this more detailed map shows a 66m summit spot height at SH 299 270 and a connecting 32m bwlch spot height, with the subsequent drop of 34m sufficient for this hill to qualify as a Dominant hill with 51.52% Dominance.  Dominant total increases by one and confirmed as 257.

Bodlondeb Wood    c 57m at SH 77923 78114 

The inclusion of this hill in the listing of Y Trechol – The Dominant Hills of Wales was on the 17.12 15 via the publication on Mapping Mountains of the hill grouping it is a part of, with a retrospective Hill Reclassifications post appearing on the 18.02.17.  The hill had previously been unclassified due to lack of detail on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps giving only a 50m uppermost ring contour and bwlch contouring between 20m – 30m,  however with the advent of 5m contour intervals on the Ordnance Survey enlarged mapping hosted on the Geograph website a more detailed estimation of its drop value and therefore its Dominance could be given, and with a drop value of c 34m based on an estimated summit height of c 57m and an estimated bwlch height of c 23m, the hill is now listed with a Dominance of 59.65%.  Dominant total increases by one and confirmed as 256. 

3^rd December 2015 – Mapping Mountains starts publication of Y Trechol – The Dominant Hills of Wales. 

Dominant total confirmed as 255.

Bryn Mawr    178.1m at SJ 25117 19054 

The wooded summit of Bryn Mawr (SJ 251 190)

The reclassification of this hill from a Lesser Dominant to a Dominant hill was due to a survey conducted by Myrddyn Phillips with the Trimble GeoXH 6000 on the 08.08.15, with its details appearing in the Carnedd Wen group of hills when published on Mapping Mountains on the 03.06.17, with a retrospective Hill Reclassifications post appearing on Mapping Mountains on 16.07.17, the hill was previously listed with 49.13% Dominance based on an estimated c 173m summit height and an estimated c 88m bwlch height, with the latter height later confirmed via an 88m spot height appearing on the Ordnance Survey enlarged mapping hosted on the Geograph website.  The subsequent survey with the Trimble produced a 178.1m (converted to OSGM15) summit height, giving this hill 90m of drop and 50.53% Dominance.  Dominant total increases by one and confirmed as 255.

Carreglefain    260.7m at SH 32421 41054 

Carreglefain (SH 324 410) is now listed as a Dominant hill after a survey with the Trimble GeoXH 6000

The announcement of this hill’s reclassification from a Lesser Dominant to a Dominant hill was made on the Mapping Mountains site on 01.12.14 with the Hill Reclassifications post being published on the 20.03.17, the hill was previously listed with 48.66% Dominance based on the 261m summit spot height on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 134m based on bwlch contouring between 130m – 140m.  This hill was subsequently surveyed with the Trimble GeoXH 6000 by Myrddyn Phillips on 24.11.14, resulting in the summit height being 260.7m (converted to OSGM15) and the bwlch height being 130.1m (converted to OSGM15), giving a drop value of 130.6m and a Dominance value of 50.08%.  Dominant total increases by one and confirmed as 254.

Castell Cricieth    49.6m at SH 50003 37733 

Castell Cricieth (SH 500 377) was accepted as a Dominant hill after its introduction into the P30 ranks

This hill was included as a Dominant hill shortly after Alex Cameron first proposed its inclusion as a new P30 in September 2014, with the hill appearing in its respective hill grouping of Moel Hebog when published on Mapping Mountains on 28.01.16 and a retrospective Hill Reclassifications post appearing on Mapping Mountains on 07.03.17.  The hill had previously been unclassified as with an uppermost 30m ring contour on Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps and bwlch contouring between 10m – 20m it was deemed not to have the minimum 3om of drop required for consideration as a Dominant hill.  However, the Ordnance Survey enlarged mapping hosted on the Geograph website has contour intervals at 5m and with a 48m summit spot height and an estimated bwlch height of c 18m, these values gave this hill c 30m of drop and 62.50% of Dominance.  The hill has subsequently been surveyed with the Trimble GeoXH 6000 by Myrddyn Phillips on the 15.06.15 with the details relating to this survey being published on Mapping Mountains on the 27.06.15, resulting in a 49.6m (converted to OSGM15) summit height and a 19.3m (converted to OSGM15) bwlch height, giving 30.3m drop and 61.02% Dominance.  Dominant total increases by one and confirmed as 253.

Llanlleiana Park    68.2m at SH 38337 94993 

Llanlleiana Park (SH 383 949) is now listed as a Lesser Dominant hill

The reclassification of this hill to a Lesser Dominant was announced on the Mapping Mountains site on 13.09.14 with the Hill Reclassifications post appearing on the 07.12.15, the hill was previously listed with 50.75% Dominance based on the 67m spot height that appears on the Ordnance Survey enlarged mapping hosted on the Geograph website and an estimated bwlch height of c 33m, with these values giving this hill c 34m of drop.  This hill was subsequently surveyed with the Trimble GeoXH 6000 by Myrddyn Phillips and Alex Cameron on 07.09.14, resulting in the summit height being 68.2m (converted to OSGM15) and the bwlch height being 34.2m (converted to OSGM15), giving a drop value of 34.0m and a Dominance of only 49.85%, which is insufficient for it to retain its Dominant status.  Dominant total decreases by one and confirmed as 252.

Ynys Glog    40.6m at SH 59647 39826 

Ynys Glog (SH 596 398) is now listed as a Dominant hill

The inclusion of this hill in the Dominant list took place shortly after Aled Williams first proposed it as a new P30 in early 2014, with a Hill Reclassifications post detailing its new status as a P30 appearing on the Mapping Mountains site on 05.02.14, the hill was subsequently listed in the Moelwynion group of Dominant hills when published on Mapping Mountains on 25.02.16, with a retrospective Hill Reclassifications post for its status as a Dominant hill appearing on the 07.04.17.  Prior to this hill being listed as a P30 it had not been classified as contouring on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps implied that it did not have the required minimum 30m of drop to be included as a P30 and therefore be considered for Dominant status.  With the advent of on-line mapping and especially the Ordnance Survey enlarged mapping hosted on the Geograph website there is now greater opportunity to analyse numerical data and with a 42m summit spot height and an estimated c 8m bwlch height on this enlarged map it gave this hill c 34m of drop and 80.95% Dominance.  The hill has subsequently been surveyed using a Trimble GeoXH 6000 by Myrddyn Phillips and Aled Williams on the 21.11.14 resulting in a 40.6m (converted to OSGM15) summit height and a 7.9m (converted to OSGM15) bwlch height, giving 32.7m of drop and 80.44% Dominance.  Dominant total increases by one and confirmed as 253.

Ynys Berfedd    42.9m at SH 59943 39865 

The wooded and rocky slopes of Ynys Berfedd (SH 599 398)

This hill was included in the Dominant list shortly after Aled Williams first proposed its inclusion as a new P30 in early 2014, with a Hill Reclassifications post detailing its new P30 status appearing on Mapping Mountains on 05.02.14, the hill then appeared in the Moelwynion group of Dominant hills when published on Mapping Mountains on 25.02.16, with a retrospective Hill Reclassifications post for its status as a Dominant hill appearing on the 06.04.17.  The hill had previously appeared in the sub list that accompanied the original Welsh P30 lists when published on Geoff Crowder’s v-g.me website, with map contouring on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps implying that it did not have the required minimum 30m of drop to be included in the main list.  However, the Ordnance Survey enlarged mapping hosted on the Geograph website has a 43m summit spot height, and with an estimated c 6m bwlch height this gave the hill c 37m of drop and sufficient Dominance to be included in Y Trechol – The Dominant Hills of Wales.  The hill has subsequently been surveyed using a Trimble GeoXH 6000 by Myrddyn Phillips and Aled Williams on the 21.11.14 resulting in a 42.9m (converted to OSGM15) summit height and a 6.8m (converted to OSGM15) bwlch height, giving 36.1m of drop and 84.06% Dominance.  Dominant total increases by one and confirmed as 252.

Ynys Hir    37.3m at SH 56695 39693 

The wooded surrounds of Ynys Hir (SH 566 396)

This hill’s inclusion as a new P30 and Dominant hill was announced on Mapping Mountains on 02.02.14 with the Hill Reclassifications post being published on the 26.02.17, the hill was previously unclassified as detail on a variety of different scaled Ordnance Survey maps implied that it did not have the minimum 30m of drop required to be considered for Dominant status.  This hill was subsequently surveyed with the Trimble GeoXH 6000 by Myrddyn Phillips and Aled Williams on the 01.02.14, and it was Aled who suggested visiting the hill and its potential as a new P30, resulting in a survey height of 37.3m (converted to OSGM15) for the summit and with an estimated bwlch height of c 3m, these values give this hill c 34m of drop and 91.21% of Dominance.  Dominant total increases by one and confirmed as 251.

Ynys Deullyn    32.6m at SM 84479 34095

This hill was added to the Dominant list shortly after its initial completion in November 2012, prior to this it was unclassified and did not appear in the P30 list on Geoff Crowder’s v-g.me website as it was thought not to have the minimum 30m of drop required for Dominant consideration, the advent of the Ordnance Survey Interactive Coverage Map hosted on the Geograph website with its greater scale and definition and importantly a 30m summit spot height meant that this hill, which is an island, qualifies for P30 status as well as Dominant status, with a retrospective Hill Reclassifications post appearing on Mapping Mountains on the 08.09.18.  The hill has since been analysed via LIDAR resulting in a 32.6m summit and 2.1m bwlch height, with these values giving this hill 30.5m of drop and 93.51% dominance.  Dominant total increases by one and confirmed as 250.

Gewni    35.7m at SM 79696 23606

Gewni (SM 796 236) from the north

This hill was added to the Dominant list shortly after its initial completion in November 2012, prior to this it was unclassified and did not appear in the P30 list on Geoff Crowder’s v-g.me website as it was thought not to have the minimum 30m of drop required for Dominant consideration, the advent of the Ordnance Survey Interactive Coverage Map hosted on the Geograph website with its greater scale and definition and importantly a 35m summit spot height meant that this hill, which is an island, qualifies for P30 status as well as Dominant status, with a retrospective Hill Reclassifications post appearing on Mapping Mountains on the 29.08.18.  The hill has since been analysed via LIDAR resulting in a 35.65m summit and 0.3m bwlch height, with these values giving this hill 35.3m of drop and 99.11% dominance.  Dominant total increases by one and confirmed as 249.

31^st November 2012 – Compilation of hand written list completed of Y Trechol – The Dominant Hills of Wales.

Dominant total confirmed as 248.

Carreg Rhoson    c 30m at SM 67235 25678

THIS HILL HAS SUBSEQUENTLY BEEN DELETED FROM DOMINANT STATUS

 

The islets making up Carreg Rhoson (SM 672 256) with the highest island now listed as a Dominant hill

This hill was the second of two added to the Dominant list shortly after its initial compilation was completed with the date of 31.10.12 recorded against the two additions, prior to this it was unclassified and did not appear in the P30 list on Geoff Crowder’s v-g.me website as its uppermost 30m ring contour on the Ordnance Survey 1:25,000 Explorer map had not been spotted, the advent of the enlarged mapping hosted on the Geograph website with its greater scale and definition meant that the small 30m ring contour was easier to see and therefore this hill, which is an island, qualifies for P30 status as well as Dominant status, with a retrospective Hill Reclassifications post appearing on the Mapping Mountains site on 09.03.17.  Dominant total increases by one and confirmed as 248.

Dinas Dinlle    34.7m at SH 43676 56438 

Dinas Dinlle (SH 436 564) is now listed in the ranks of Dominant hills

This hill was one of two added to the Dominant list shortly after its initial compilation with the date of 31.10.12 recorded against the two additions, prior to this its potential inclusion as a P30 was first spotted by Chris Watson, with the hill appearing in its respective hill grouping when published on Mapping Mountains on 28.01.16 and a retrospective Hill Reclassifications post appearing on Mapping Mountains on 24.02.17.  The hill had previously been unclassified with a 31m summit spot height on the Ordnance Survey 1:50,000 Landranger and bwlch contouring between 0m – 10m on this and the 1:25,000 Explorer map, these details implied that the hill did not have 30m of drop which is the minimum required for consideration to Dominant status.  However, the Ordnance Survey enlarged mapping hosted on the Geograph website has contour intervals at 5m and with an uppermost ring contour of 35m and bwlch contouring between 0m – 5m it meant that this hill had sufficient prominence and dominance to be included in this list.  The hill’s summit was subsequently surveyed with the Trimble GeoXH 6000 by Myrddyn Phillips and Bryn Phillips on the 26.12.13 with the details relating to this survey being published on Mapping Mountains on the 03.01.14, with the 34.7m (converted to OSGM15) summit height and a 4.1m bwlch height, with the latter ascertained from LIDAR analysis, these values give this hill 30.6m of drop and 88.22% dominance.  Dominant total increases by one and confirmed as 247.

Pen Twmp    217m at SM 988 329

This hill’s reclassification from Dominant to Lesser Dominant status took place after 22.03.12 and was retrospectively reported on Mapping Mountains with a Hill Reclassifications post on the 09.08.18.  The hill had previously been classified with 50.69% Dominance based on the 217m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 107m based on interpolation of bwlch contouring between 105m – 110m, this drop value was amended when the Ordnance Survey Interactive Coverage Map hosted on the Geograph website became available online, and as this scale of mapping shows a 109m spot height on the area of this hill’s bwlch this amended the drop value of the hill to 108m and its Dominance to 49.77% and it was therefore reclassified from a Dominant to a Lesser Dominant hill.  This hill has subsequently been analysed via LIDAR resulting in a 108.3m bwlch height and its reinstatement as a Dominant hill (see above).  Dominant total decreases by one and confirmed as 246.

Cae Quarry    70.9m at SN 50644 20918

LIDAR image of Cae Quarry (SN 506 209)

The reclassification of this hill from Dominant to Lesser Dominant status took place after 22.03.12 and was retrospectively reported on Mapping Mountains with a Hill Reclassifications post on the 04.03.18.  The hill had previously been classified with 50.00% Dominance based on the 68m summit spot height and an estimated bwlch height of c 34m, with the latter based on 10m contour intervals on the Ordnance Survey 1:25,000 Explorer map, this drop value was amended when the Ordnance Survey Interactive Coverage Map hosted on the Geograph website became available and was examined, and as this scale of mapping has 5m contour intervals for the area surrounding this hill it altered its drop value to an estimated c 31m, and its Dominance to 45.59%.  The hill was subsequently analysed via LIDAR, resulting in a 70.9m summit height and a 36.1m bwlch height, with these values giving this hill 34.8m of drop and 49.04% dominance.  Dominant total decreases by one and confirmed as 247.

Ynys Gron    69.4m at SH 59653 39268 

The Trimble GeoXH 6000 gathering data at the highest point of what remains of Ynys Gron (SH 596 392)

This hill was deleted from the Dominant list after 22.03.12 and was retrospectively reported on Mapping Mountains with a Hill Reclassifications post on the 05.04.17, with the hill having been excluded from the Moelwynion group of hills when these were published on Mapping Mountains on the 25.02.16.  The hill had previously been classified with 52.08% Dominance based on the Ordnance Survey 96m summit spot height on the 1:25,000 Outdoor Leisure map and an estimated drop of c 50m, this was reassessed when more up-to-date on-line mapping became available that showed this hill’s summit to have been quarried.  The hill has subsequently been surveyed using a Trimble GeoXH 6000 by Myrddyn Phillips on the 25.11.14, resulting in a 69.4m (converted to OSGM15) summit height and a 44.3m (converted to OSGM15) bwlch height, with these values giving this hill 25.1m of drop, which is insufficient for it to be considered for Dominant status.  Dominant total decreases by one and confirmed as 248.

Geirth Mawr    57.4m at SH 53511 39363 

LIDAR image of Geirth Mawr (SH 535 393)

The deletion of this hill from Dominant status took place after 22.03.12 and was reported on Mapping Mountains with a Hill Reclassifications post published on the 21.02.17, with the hill having been excluded from the Moel Hebog group when these were published on the 28.01.16.  When the original 30-99m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 category.  When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with an estimated c 30m of drop, based on an estimated c 58m summit height, based on interpolation of 10m contouring and the 28m bwlch spot height that appears on the Ordnance Survey 1:25,000 Explorer map, resulting in a dominance value of 51.72%, which was sufficient for Dominant status.  The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had a 56m summit spot height, resulting in its drop value being amended to 28m, which is insufficient for continued Dominant status.  The hill has now been analysed via LIDAR, resulting in a 57.4m summit height and a 27.9m bwlch height, with these values giving this hill 29.5m of drop.  Dominant total decreases by one and confirmed as 249.

11^th April 2011 – Started compilation of hand written list of Y Trechol – The Dominant Hills of Wales.

Dominant total confirmed as 250.

23^rd April 2009 – Criteria established and first hill purposely bagged that met the criteria of Y Trechol – The Dominant Hills of Wales.

Dominant total confirmed as 250.

Myrddyn Phillips (August 2017)