Mapping Mountains – Hill Reclassifications – Y Trechol – The Dominant Hills of Wales

Y Trechol – The Dominant Hills of Wales – Hill Reclassifications

Y Trechol –The Dominant Hills of Wales are the Welsh P30 hills whose prominence equal or exceed half that of their absolute height, accompanying the Dominant list is a sub list entitled The Lesser Dominant Hills of Wales with the criteria for this sub category being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list commenced publication on Mapping Mountains on 03.012.15 with its initial Introduction giving details to its compilation and criteria.  

The list is authored by Myrddyn Phillips and the posts that have appeared on Mapping Mountains detailing the additions, reclassifications and deletions to the Dominant and Lesser Dominant list appear below presented chronologically in receding order.

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Allt Dan Tŷ Mawr (SN 520 228) – Lesser Dominant addition (35th reclassification)

Significant Height Revisions post for Allt Dan Tŷ Mawr

 

There has been confirmation of an addition to the listing of Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Allt Dan Tŷ Mawr (SN 520 228)

The criteria for the list that this addition applies to are: 

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format. 

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Allt Dan Tŷ Mawr and it is adjoined to the Mynydd Mallaen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north, west and south, and the A40 road to its south-west, and has the town of Llandeilo towards the east. 

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 in 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 29m of drop, based on an estimated c 67m summit height and the 38m bwlch spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

Extract from the Ordnance Survey 1:25,000 Explorer map

Since the original publication of the Welsh P30 lists on Geoff Crowder’s v-g.me website there have been a number of maps made available online.  Some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website.  Whilst others were digitally updated such as the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map, whilst others are current and digitally updated such as the interactive mapping on the Magic Maps and WalkLakes websites. 

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 69m summit spot height positioned at SN 51824 22804, and when coupled with the 38m bwlch spot height these values gave this hill 31m of drop and 44.93% dominance. 

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

Therefore, the confirmation of the addition of this hill to Lesser Dominant status is due to LIDAR analysis, resulting in a 72.65m summit height and a 39.0m bwlch height, with these values giving this hill 33.7m of drop and 46.32% dominance, which is sufficient for it to be classified as a Lesser Dominant hill.

 

The full details for the hill are:

Group:  Mynydd Mallaen

Name:  Allt Dan Tŷ Mawr

OS 1:50,000 map:  159

Summit Grid Reference:  SN 52004 22867 (LIDAR)

Summit Height:  72.65m (LIDAR)

Bwlch Grid Reference:  SN 52223 22857 (LIDAR)

Drop Summit to Bwlch:  33.7m (LIDAR)

Drop Bwlch to ODN:  39.0m (LIDAR)

Dominance:  46.32% (LIDAR)

Myrddyn Phillips (March 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Cae Cwarre (SN 506 209) – Dominant reclassified to Lesser Dominant (34th reclassification)

Significant Height Revisions post for Cae Cwarre

Significant Name Changes post for Cae Cwarre

There has been a reclassification to the listing of Y Trechol – The Dominant Hills of Wales which has resulted in this hill being reclassified to the Lesser Dominant list due to its drop value being amended.

LIDAR image of Cae Cwarre (SN 506 209)

The details relating to this hill’s reclassification as a Lesser Dominant are retrospective as it was originally included in the Dominant list with the date of 24.01.12 given to the completion of this segment of the list, but it was soon noted that it should be transferred to the Lesser Dominant list.

The criteria for inclusion to the Dominant list being those Welsh P30 hills whose prominence equal or exceed half that of their absolute height, whilst the criteria for the Lesser Dominant list are those additional Welsh P30s whose prominence is 33% or more and below 50% of their absolute height.

During 2006 and 2007 the sub category of hills accompanying the Welsh P30 lists published on Geoff Crowder’s v-g.me website were standardised and interpolated drop values also added, this hill was then listed with an estimated c 34m of drop based on its 68m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 34m, based on 10m bwlch contouring between 30m – 40m, with these values giving this hill 50.00% Dominance.

Within two months of this segment of the list being completed I was informed about the Ordnance Survey Interactive Coverage map hosted on the Geograph website, and as this map has 5m contour intervals for the area of this hill it meant that the hill’s drop value now altered, whereas it had been listed as c 34m based on an estimated bwlch height of c 34m, the bwlch contouring was now between 35m – 40m and the bwlch height estimated as c 37m, giving this hill c 31m of drop and 45.59% Dominance.

The name the hill is listed by is Cae Cwarre, with this name derived from the Tithe map and it is adjoined to the Mynydd Mallaen group of hills which are situated in the Region of Mid and West Wales (Region B, Sub-Region B2).  The hill is positioned above the Afon Cothi to its west and the Afon Tywi (River Towy) to its south, and has the small community of Llanegwad to its east north-east.

As the hill is not a part of designated open access land permission to visit should be sought, for those wishing to do so the nearest public footpath leaves a minor lane just to the south of the summit.

The reclassification of Cae Cwarre to Lesser Dominant status was initially dependent upon the 5m contour intervals given on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website, and subsequently confirmed via LIDAR analysis, resulting in a summit height of 70.9m and a bwlch height of 36.1m, with these values giving this hill 34.8m of drop and 49.04% dominance, which is sufficient for Lesser Dominant status.

The full details for the hill are: 

Group:  Mynydd Mallaen 

Name:  Cae Cwarre 

Dominance:  49.04% (LIDAR) 

OS 1:50,000 map:  159 

Summit Grid Reference:  SN 50644 20918 (LIDAR) 

Summit Height:  70.9m (LIDAR) 

Drop Summit to Bwlch:  34.8m (LIDAR)

Drop Bwlch to ODN:  36.1m (LIDAR) 

Myrddyn Phillips (March 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Bryn y Gwynt (SH 599 449) – Dominant addition (33rd reclassification)

Significant Name Changes post for Bryn y Gwynt

Significant Height Revisions post for Bryn y Gwynt

Summit Relocations post for Bryn y Gwynt

There has been an addition to a hill that is now listed in the Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height, their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Aled Williams and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and Aled Williams.

LIDAR image of Bryn y Gwynt (SH 599 449)

The criteria for the list that this addition applies to are:

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height, with the Introduction to the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format.

The name the hill is listed by is Bryn y Gwynt and this was derived from local enquiry and the series of Ordnance Survey Six-Inch maps and it is situated in the Moelwynion range of hills in the Region of North Wales (Region A, Sub-Region A1), and is positioned with the A 4085 road to its north-east and has the Welsh Highland Railway to its immediate west and overlooks the Afon Glaslyn also to its west, and has the village of Beddgelert to its north north-west and the town of Porthmadog to its south south-west.

The hill is a part of Coed Hafod y Llyn, and as this name implies its summit is placed in woodland which is deciduous, and as the summit of the hill is not a part of designated open access land permission to visit should be sought, however paths are indicated on the map to the north, east and south of this hill’s summit and therefore gaining access to its lower slopes has probably been accepted for many years.

Prior to LIDAR analysis this hill was listed in the Hills to be surveyed sub list that accompanied the Welsh P30 lists published on Geoff Crowder’s v-g.me website.  When these sub lists were standardised and also drop values added, this hill was listed with an estimated c 29m of drop based on the 56m spot height that appears on the Ordnance Survey 1:25,000 Explorer map at SH 59881 44828 and an estimated bwlch height of c 27m based on contouring at 10m intervals between 20m – 30m, with the caveat that the 27m spot height that appears on a road at SH 60168 45293 on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website is judged not to be positioned at the critical bwlch.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

LIDAR analysis confirms Bryn y Gwynt to be a Dominant hill, and as the summit has now been surveyed with the Trimble GeoXH 6000, it is this result that is being prioritised for listing purposes.

The Trimble GeoXH 6000 gathering data at the summit of Bryn y Gwynt

Therefore, the addition of this hill to the Y Trechol - The Dominant Hills of Wales list is due to LIDAR analysis and a subsequent Trimble GeoXH 6000 survey, resulting in a 59.9m summit height and a 28.0m bwlch height, with these values giving this hill 31.9m of drop and 53.21% dominance, which is sufficient for it to be classified as a Dominant hill.

The full details for the hill are:

Group:  Moelwynion

Name:  Bryn y Gwynt

OS 1:50,000 map:  124

Summit Height:  59.9m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 59949 44919 (Trimble GeoXH 6000) 

  

Bwlch Height:  28.0m (LIDAR)

Bwlch Grid Reference:  SH 60224 45248 & SH 60226 45258 & SH 60227 45259 (LIDAR)

Drop:  31.9m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  53.21% (Trimble GeoXH 6000 summit and LIDAR bwlch)

My thanks to Aled Williams for sending the details of this hill to me.

Myrddyn Phillips (January 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Castell (SN 585 790) – Lesser Dominant addition (32nd reclassification)

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales, resulting in this hill being added to the Lesser Dominant list due to its drop value being amended.

With the criteria for inclusion to the Dominant list being those Welsh P30 hills whose prominence equal or exceed half that of their absolute height, whilst the criteria for the Lesser Dominant list are those additional Welsh P30s whose prominence is 33% or more and below 50% of their absolute height.

During 2006 and 2007 the sub category of hills accompanying the Welsh P30 lists published on Geoff Crowder’s v-g.me website were standardised and interpolated drop values also added, this hill was then listed with an estimated c 29m of drop based on its 73m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 44m, therefore as the drop value was under 30m it was insufficient for this hill to qualify for either the Dominant or Lesser Dominant list.  The drop value was subsequently altered to 31m due to a 41m bwlch spot height appearing on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website.

The name of the hill is Castell and it is adjoined to the Elenydd group of hills which are situated in the Region of Mid and West Wales (Region B, Sub-Region B2).  The hill is positioned above the Afon Ystwyth which encircles it on its eastern side, and has the town of Aberystwyth to its north.

As the hill is not a part of designated open access land permission to visit should be sought, for those wishing to do so the nearest public footpath leaves a minor lane to the hill’s south-east and contours around the northern base of the hill.

The qualification of Castell to Lesser Dominant status is dependent upon Ordnance Survey spot heights, with a summit spot height of 73m and a bwlch spot height of 42m given on the Interactive Coverage map hosted on the Geograph website, with these values giving this hill 31m of drop and 42.47% Dominance, which is sufficient for this hill to be listed as a Lesser Dominant hill.

The full details for the hill are:

Group:  Elenydd

Name:  Castell

Dominance:  42.47%

OS 1:50,000 map:  135

Summit Grid Reference:  SN 58519 79005

Summit Height:  73m

Drop Summit to Bwlch:  31m

Drop Bwlch to ODN:  42m  

Myrddyn Phillips (January 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Copa Shon (SN 781 993) – Lesser Dominant addition (31st reclassification)

Survey post for Copa Shon

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales initiated by a survey with the Trimble GeoXH 6000, resulting in this hill being added to the Lesser Dominant list. 

The criteria for this listing are:

Y Trechol – The Dominant Hills of Wales - Welsh P30s whose prominence equal or exceed half that of their absolute height, with the criteria for Lesser Dominant status being those additional Welsh P30s whose prominence is 33% or more and below 50% of their absolute height.

This hill’s addition to Lesser Dominant status was dependent upon a survey with the Trimble GeoXH 6000 which was conducted by Myrddyn Phillips on the 29^th October 2017, with the relevant post giving the survey details appearing on Mapping Mountains on the 31^st December 2017.

Prior to the survey with the Trimble GeoXH 6000 this hill’s twin 217m map heighted summit of Pen y Graig Fawr which is positioned at SN 77352 99601 was prioritised as being listed as a Lesser Dominant.  The survey with the Trimble separated these twin map heighted tops and resulted in the deletion of Pen y Graig Fawr and the addition of Copa Shon to Lesser Dominant status.

The name of the hill is Copa Shon and it is adjoined to the Pumlumon range of hills which are situated in Mid and West Wales (Region B, Sub-Region B2).  The hill overlooks the A 489 road to the north and the Afon Dulas which is to the south, with the town of Machynlleth to the west north-west. 

As the summit of the hill is not on designated open access land permission to visit should be sought, however the land to the south of the summit is a part of open access land and comes very close to the high point of the hill, because of this common sense should prevail for those wishing to visit its summit.

The addition of Copa Shon to Lesser Dominant status was confirmed by a survey with the Trimble GeoXH 6000, resulting in a summit height of 217.3m (converted to OSGM15) and a bwlch height of 127.9m (converted to OSGM15), and as this hill is 0.50m higher than Pen y Graig Fawr (SN 773 996) it gives Copa Shon 89.5m of drop and 41.16% Dominance, which is sufficient for it to be listed as a Lesser Dominant hill.

The full details for the hill are:

Group:  Pumlumon

Name:  Copa Shon

Dominance:  41.16%

OS 1:50,000 map:  135

Summit Grid Reference:  SN 78108 99347

Summit Height:  217.3m (converted to OSGM15)

Drop Summit to Bwlch:  89.5m

Drop Bwlch to ODN:  217.3m (converted to OSGM15) 

Copa Shon (SN 781 993) is now added to the ranks of Lesser Dominant hills

For details on the survey that resulted in the addition of this hill to Lesser Dominant status

Myrddyn Phillips (January 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Pen y Graig Fawr (SN 773 996) – Lesser Dominant deletion (30th reclassification)

Survey post for Pen y Graig Fawr

There has been a deletion from the listing of Y Trechol – The Dominant Hills of Wales initiated by a survey with the Trimble GeoXH 6000, resulting in this hill being deleted from the Lesser Dominant list. 

The criteria for this listing are:

Y Trechol – The Dominant Hills of Wales - Welsh P30s whose prominence equal or exceed half that of their absolute height, with the criteria for Lesser Dominant status being those additional Welsh P30s whose prominence is 33% or more and below 50% of their absolute height.

This hill’s deletion from Lesser Dominant status was dependent upon a survey with the Trimble GeoXH 6000 which was conducted by Myrddyn Phillips on the 29^th October 2017, with the relevant post giving the survey details appearing on Mapping Mountains on the 31^st December 2017.

Prior to the survey with the Trimble GeoXH 6000 this hill was prioritised as being listed as a Lesser Dominant over its twin 217m map heighted summit of Copa Shon which is positioned at SN 78108 99347.  The survey with the Trimble separated these twin map heighted tops and resulted in the deletion of Pen y Graig Fawr and the addition of Copa Shon to Lesser Dominant status.

The name of the hill is Pen y Graig Fawr and it is adjoined to the Pumlumon range of hills which are situated in Mid and West Wales (Region B, Sub-Region B2).  The hill overlooks the A 489 road to the north and the Afon Dulas which is to the south, with the town of Machynlleth to the west north-west. 

As the summit of the hill is not on designated open access land permission to visit should be sought, however the land to the south of the summit is a part of open access land and comes very close to the high point of the hill, because of this common sense should prevail for those wishing to visit its summit.

The deletion of Pen y Graig Fawr from Lesser Dominant status was confirmed by a survey with the Trimble GeoXH 6000, resulting in a summit height of 216.8m (converted to OSGM15) and a bwlch height of 182.4m (converted to OSGM15), and as this hill is 0.50m lower than Copa Shon (SN 781 993) it gives Pen y Graig Fawr 34.4m of drop and 15.88% Dominance, which is insufficient for its continued inclusion in the Lesser Dominant list.

The full details for the hill are:

Group:  Pumlumon

Name:  Pen y Graig Fawr

Dominance:  15.88%

OS 1:50,000 map:  135

Summit Grid Reference:  SN 77352 99601

Summit Height:  216.8m (converted to OSGM15)

Drop Summit to Bwlch:  34.4m

Drop Bwlch to ODN:  182.4m (converted to OSGM15) 

Pen y Graig Fawr (SN 773 996) is now deleted from the ranks of Lesser Dominant hills

For details on the survey that resulted in the deletion of this hill from Lesser Dominant status

Myrddyn Phillips (January 2018)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Gelli Hir (SN 999 883) – Lesser Dominant addition (29th reclassification)

1st survey post for Gelli Hir

2nd survey post for Gelli Hir

Significant Name Changes post for Gelli Hir

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales with the summit height confirmed by a survey with the Trimble GeoXH 6000 and later substantiated by a survey with the Leica GS15, and the bwlch height later ascertained from LIDAR analysis conducted by Myrccyn Phillips, resulting in this hill being added to the Lesser  Dominant list.  

The criteria for this listing are:

Y Trechol – The Dominant Hills of Wales - Welsh P30s whose prominence equal or exceed half that of their absolute height, with the criteria for Lesser Dominant status being those additional Welsh P30s whose prominence is 33% or more and below 50% of their absolute height.

The details relating to this hill’s addition to the Lesser Dominant list are retrospective as the confirmation was dependent upon a survey with the Trimble GeoXH 6000 which was conducted by Myrddyn Phillips on the 7^th February 2014, the result was later substantiated by a survey with the Leica GS15 which was conducted by John Barnard, Graham Jackson and Myrddyn Phillips on the 2^nd May 2014.

Prior to the survey with the Trimble GeoXH 6000 this hill’s twin 308m map heighted summit of Y Gaer which is positioned at SO 01350 87380 was prioritised as being listed as a Lesser Dominant.  The survey with the Trimble separated these twin map heighted tops and resulted in the deletion of Y Gaer, and the addition of Gelli Hir to Lesser Dominant status.

The name of the hill is Gelli Hir and it is adjoined to the Pumlumon range of hills which are situated in Mid and West Wales (Region B, Sub-Region B2).  The hill has the A 470 road and the Afon Hafren (River Severn) to its east, and is positioned between the small community of Caersws to the north-east and the town of Llanidloes towards the south-west. 

As the summit of the hill is not on designated open access land permission to visit should be sought, however as a public footpath traverses this hill’s elongated and broad summit ridge in a north – south direction and passes close to the high point of the hill, common sense should prevail as a diversion to the summit is only a short distance away.

The addition of Gelli Hir to Lesser Dominant status was confirmed by a survey with the Trimble GeoXH 6000 and then substantiated by a survey with the Leica GS15, resulting in a summit height of 307.2m (converted to OSGM15) which is 0.1m higher than its twin map heighted summit of Y Gaer (SO 013 873), with LIDAR analysis giving the height of the bwlch as 182.5m, resulting in 124.7m of drop and 40.60% dominance this hill is added to the Lesser Dominant list.

The full details for the hill are:

Group:  Pumlumon

Name:  Gelli Hir

Dominance:  40.60% (Leica GS15 summit and LIDAR bwlch)

OS 1:50,000 map:  136

Summit Grid Reference:  SN 99903 88383 (Leica GS15)

Summit Height:  307.2m (converted to OSGM15, Leica GS15)

Drop Summit to Bwlch:  124.7m (Leica GS15 summit and LIDAR bwlch)

Drop Bwlch to ODN:  182.5m (LIDAR) 

Gelli Hir (SN 999 883) is now added to the ranks of Lesser Dominant hills

For details on the survey that resulted in the addition of this hill to Lesser Dominant status

Myrddyn Phillips (December 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Y Gaer (SO 013 873) – Lesser Dominant deletion (28th reclassification)

1st survey post for Y Gaer

2nd survey post for Y Gaer

Significant Name Changes post for Y Gaer

There has been a deletion from the listing of Y Trechol – The Dominant Hills of Wales confirmed by a survey with the Trimble GeoXH 6000 and later substantiated by a survey with the Leica GS15, resulting in this hill being deleted from the Lesser  Dominant list. 

The criteria for this listing are:

Y Trechol – The Dominant Hills of Wales - Welsh P30s whose prominence equal or exceed half that of their absolute height, with the criteria for Lesser Dominant status being those additional Welsh P30s whose prominence is 33% or more and below 50% of their absolute height.

The details relating to this hill’s deletion from the Lesser Dominant list are retrospective as the confirmation was dependent upon a survey with the Trimble GeoXH 6000 which was conducted by Myrddyn Phillips on the 7^th February 2014, the summit result was later substantiated by a survey with the Leica GS15 which was conducted by John Barnard, Graham Jackson and Myrddyn Phillips on the 2^nd May 2014.

Prior to the survey with the Trimble GeoXH 6000 this hill was prioritised as being listed as a Lesser Dominant over its twin 308m map heighted summit of Gelli Hir which is positioned at SN 99903 88383.  The survey with the Trimble separated these twin map heighted tops and resulted in the deletion of Y Gaer, and the addition of Gelli Hir to Lesser Dominant status.

The name of the hill is Y Gaer and it is adjoined to the Pumlumon range of hills which are situated in Mid and West Wales (Region B, Sub-Region B2).  The hill overlooks the A 470 road and the Afon Hafren (River Severn) which is to its east, with the small community of Llandinam at the base and to the north-east of the hill and the town of Llanidloes towards the west south-west.  

As the summit of the hill is not on designated open access land permission to visit should be sought, however as a public footpath traverses this hill’s elongated and broad summit ridge in a north-east to south-west orientation and passes close to the high point of the hill, common sense should prevail and a diversion to the summit is only a short distance away.

The deletion of Y Gaer from Lesser Dominant status was confirmed by a survey with the Trimble GeoXH 6000 and the summit result was later substantiated by a survey with the Leica GS15, resulting in a summit height of 307.1m (converted to OSGM15) and a bwlch height of 215.8m (converted to OSGM15), which gives this hill 91.4m of drop and 29.74% Dominance, which is insufficient for its continued inclusion in the Lesser Dominant list.

The full details for the hill are:

Group:  Pumlumon

Name:  Y Gaer

Dominance:  29.74%

OS 1:50,000 map:  136

Summit Grid Reference:  SO 01350 87380

Summit Height:  307.1m (converted to OSGM15)

Drop Summit to Bwlch:  91.3m (converted to OSGM15)

Drop Bwlch to ODN:  215.8m 

Y Gaer (SO 013 873) is now deleted from the ranks of Lesser Dominant hills

For details on the survey that resulted in the deletion of this hill from Lesser Dominant status 

Myrddyn Phillips (December 2017) 

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Coed y Gaer (SO 004 843) – Lesser Dominant addition (27th reclassification)

Survey post for Coed y Gaer

Significant Height Revisions post for Coed y Gaer

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales prompted by a survey with the Trimble GeoXH 6000 and confirmed by subsequent LIDAR analysis; resulting in this hill being included in the Lesser Dominant sub list.

With the criteria for inclusion to the Dominant list being those Welsh P30 hills whose prominence equal or exceed half that of their absolute height, whilst the criteria for the Lesser Dominant list are those additional Welsh P30s whose prominence is 33% or more and below 50% of their absolute height.

The details relating to the inclusion of this hill in the Lesser Dominant category are retrospective as the confirmation of its addition is dependent upon a survey with the Trimble GeoXH 6000 which was conducted on the 9^th February 2014, with the relevant post giving the survey details appearing on Mapping Mountains on the 11^th February 2014.

When the sub category of hills accompanying the Welsh P30 lists published on Geoff Crowder’s v-g.me website were standardised with interpolated drop values, this hill was listed with an estimated c 119m of drop based on its 362m summit spot height and an estimated bwlch height of c 243m, these values gave this hill 32.87% dominance, which was insufficient for it to be classified as a Lesser Dominant hill.  The drop value was subsequently altered due to a 241m bwlch spot height appearing on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map, this resulted in the dominance of the hill also being amended.

The name the hill is listed by is Coed y Gaer and it is adjoined to the Hirddywel group and is placed in the Region of Mid and West Wales (Region B, Sub-Region B1) with its Cardinal Hill being Pegwn Mawr (SO 023 812), and is situated above the A 470 road and the Afon Hafren (River Severn) which are to its north, and it is positioned between the small community of Llandinam to the north north-east and the town of Llanidloes to the west.

As the hill is not a part of designated open access land permission to visit should be sought, for those wishing to do so a minor lane to the south of the hill gives access to steep slopes leading to the summit.

Therefore, the addition of Coed y Gaer to Lesser Dominant status was prompted by a Trimble GeoXH 6000 survey and subsequently confirmed by LIDAR analysis, resulting in a 361.0m summit height and a 239.5m bwlch height, with these values giving this hill 121.5m of drop and 33.65% of dominance.

LIDAR image of Coed y Gaer (SO 004 843)

  

The full details for the hill are:

Group:  Hirddywel

Name:  Coed y Gaer

Dominance:  33.65% (LIDAR)

OS 1:50,000 map:  136

Summit Grid Reference:  SO 00491 84393 (LIDAR)

Summit Height:  361.0m (LIDAR)

Drop Summit to Bwlch:  121.5m (LIDAR)

Drop Bwlch to ODN:  239.5m (LIDAR)

For details on the survey that confirmed the addition of this hill to Lesser Dominant status

Myrddyn Phillips (August 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Bryn Mawr (SJ 251 190) – Lesser Dominant reclassified to Dominant (26th reclassification)

Survey post for Bryn Mawr

Significant Height Revisions post for Bryn Mawr

There has been a reclassification to the listing of Y Trechol – The Dominant Hills of Wales; resulting in this hill being reclassified from a Lesser Welsh Dominant to a Dominant hill.  With the criteria for inclusion to the Dominant list being those Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

The details relating to this hill’s inclusion as a Dominant hill are retrospective as its reclassification was dependent upon a survey with the Trimble GeoXH 6000 which was conducted on the 8^th August 2015, with its details appearing in the Carnedd Wen group of hills when published on the Mapping Mountains site on the 3rd June 2017.

Prior to this hill’s inclusion as a Dominant hill it was listed as a Lesser Welsh Dominant hill with 49.13% Dominance based on an estimated c 173m summit height and an estimated bwlch height of c 88m, which gave this hill c 85m of drop.  The bwlch height was later revised to 88m based on the spot height that appears on the Ordnance Survey enlarged mapping hosted on the Geograph website; this revision did not alter this hill’s Dominance value.

The hill is listed in the Carnedd Wen group and is placed in the Region of North Wales (Region A, Sub-Region A4) with its Cardinal Hill being Y Golfa (SJ 182 070), and is situated above the B 4393 road which is to its north and east and the A 483 road to its south-east, and has the Montgomery Canal to its east and the Afon Efyrnwy (River Vyrnwy) to its north, and is positioned between the small communities of Llansantffraid-ym-Mechain to the west north-west, Llanymynech to the north-east, Four Crosses to the east south-east and Ardllin (Arddleen) towards the south.

As the hill is not a part of designated open access land permission to visit should be sought, with the nearest public footpath situated to the north-east of the summit, which consists of overgrown undergrowth and trees.

The name of the hill is Bryn Mawr and it qualifies for Dominant status based on the survey with the Trimble GeoXH 6000 resulting in a summit height of 178.1m (converted to OSGM15) which when coupled with its 88m bwlch spot height gives this hill 90m of drop and 50.53% Dominance.

  

The full details for the hill are:

Group:  Carnedd Wen

Name:  Bryn Mawr

Dominance:  50.53%

OS 1:50,000 map:  126

Summit Grid Reference:  SJ 25117 19054

Summit Height:  178.1m (converted to OSGM15)

Drop Summit to Bwlch:  90m

Drop Bwlch to ODN:  88m 

Bryn Mawr (SJ 251 190) now reclassified to a Dominant hill

For details on the survey that reclassified this hill to Dominant status

Myrddyn Phillips (July 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Carn Ysgubor (SM 699 246) – Dominant reclassified to Lesser Dominant (25th reclassification)

Survey post for Carn Ysgubor

Please note; Carn Ysgubor was originally listed as a Lesser Dominant based on map detail, it was then reclassified to a Dominant based on a survey with the Trimble GeoXH 6000, since this survey the Ordnance Survey have adopted OSGM15, this remodelling has altered the known accurate height of Welsh hills by approximately 2-4cm, and the conversion to OSGM15 of data produced by the Trimble for Carn Ysgubor has resulted in this hill being reclassified back to the ranks of Lesser Dominant hills.

There has been a reclassification to the listing of Y Trechol – The Dominant Hills of Wales which has resulted in this hill being reinstated to The Lesser Dominant Hills of Wales list due to a survey with the Trimble GeoXH 6000 and the subsequent conversion of these data to OSGM15. 

The details relating to this hill’s reclassification and reinstatement as a Lesser Welsh Dominant are retrospective as the survey with the Trimble GeoXH 6000 took place on the 15^th May 2016 and the conversion of data to OSGM15 was instigated on Mapping Mountains shortly after 30^th August 2016.

The criteria for Dominant status are those Welsh P30s whose prominence equal or exceed 50% of their absolute height, whilst the criteria for Lesser Dominant status are those additional Welsh P30s whose prominence is 33% or more and below 50% of their absolute height.

The hill was originally listed as a Lesser Dominant with 49.50% Dominance based on the 101m summit spot height that appears on Ordnance Survey 1:25,000 Explorer maps and an estimated bwlch height of c 51m, with these values giving the hill c 50m of drop. 

The hill was subsequently reclassified to a Dominant with 50.00% Dominance based on a survey with the Trimble GeoXH 6000 resulting in a 102.4m (102.369m) summit height and a 51.2m (51.182m) bwlch height, with these values giving this hill 51.2m (51.187m) of drop and 50.00244% of Dominance.

The hill is listed in the Pembrokeshire Islands group and is placed in the Region of Mid and West Wales (Region B, Sub-Region B4) with its Cardinal Island being Ynys Dewi, the hill is positioned on the northern part of Ynys Dewi, this island is also commonly known as Ramsey, and is situated to the west of St David’s in the south-west of Wales.

As the hill is situated on an island the only way to approach is via boat and the only company with permission to land on Ynys Dewi is Thousand Island Adventures (tel: 01437-721721).  The hill can be easily accessed from where the boat docks as a gravelled track leads up to The Farmhouse from where a vehicle path heads toward The Bungalow, which is a house on the eastern slopes of the hill.  A narrower path leaves this main route and heads toward the summit of the hill.

The name of the hill is Carn Ysgubor, with its composition presented as Carnysgubor on current Ordnance Survey maps, and it has been reclassified and reinstated to The Lesser Dominant Hills of Wales list as the conversion using OSGM15 has resulted in an increase of 0.026m in both its summit and bwlch heights as surveyed using the Trimble GeoXH 6000, with the summit height amended from 102.369m to 102.395m and the bwlch height amended from 51.182m to 51.208m.  The increase in heights has also affected the Dominance of the hill from 50.00% to 49.99% and therefore Carn Ysgubor is reclassified from a Dominant to a Lesser Dominant hill.  

Carn Ysgubor is only the third hill that I know of whose status has been altered due to the Ordnance Survey remodelling known as OSGM15.  This remodelling has increased the accurately known height of hills in Wales by approximately 2-4cm, and the other two hills whose status has been altered through the conversion to OSGM15 are Calf Top (SD 664 856) and Pen y Gaer (SO 139 976).

The full details for the hill are:

Group:  Pembrokeshire Islands

Name:  Carn Ysgubor

Dominance:  49.99%

OS 1:50,000 map:  157

Summit Grid Reference:  SM 69953 24603

Summit Height:  102.4m (converted to OSGM15)

Drop Summit to Bwlch:  51.2m

Drop Bwlch to ODN:  51.2m (converted to OSGM15) 

Carn Ysgubor (SM 699 246) has now been reclassified and reinstated to the Lesser Dominant list due to a survey with the Trimble GeoXH 6000 and the conversion of data to OSGM15

For details on the survey that resulted in this hill being reclassified from a Dominant to a Lesser Dominant hill

Myrddyn Phillips (July 2017)






Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Pt. 259m (SJ 181 438) – Lesser Dominant addition (24th reclassification)

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales which has resulted in this hill being added to the Lesser Welsh Dominant list.  The criteria for inclusion in this category of sub list is those P30 hills whose prominence is 33% or more and below 50% of their absolute height.

The details relating to this hill’s inclusion as a Lesser Welsh Dominant are retrospective as it appeared in the Y Berwyn group of hills when published on the Mapping Mountains site on the 3rd March 2017.

The hill did not appear in the original listing of Y Trechol – The Dominant Hills of Wales as it was listed with an estimated c 86m of drop, and when coupled with its 259m summit spot height that appeared on the Ordnance Survey 1:25,000 Explorer map it gave this hill 33.20% Dominance, which was just under the minimum required to be classified as a Lesser Welsh Dominant hill.

The hill is listed in the Y Berwyn group and is placed in the Region of North Wales (Region A, Sub-Region A4) with its Cardinal Hill being Moel Fferna (SJ 116 397), and is almost encircled by the Afon Dyfrdwy (River Dee) and is situated with the town of Llangollen to the east south-east.

If wanting to visit the hill the upper section is a part of designated open access land and it can be easily accessed from a track that leaves the A5 road which is positioned to the south of the summit.

The hill is being listed under the point (Pt. 259m) notation as I do not know an appropriate name for it either from local enquiry or historical research, and it qualifies for Lesser Welsh Dominant status based on a re-interpolation of its bwlch height which gives the hill a drop of 87m and a Dominance of 33.59%.

The full details for the hill are:

Group:  Y Berwyn

Name:  Pt. 259m

Dominance:  33.59%

OS 1:50,000 map:  125

Summit Grid Reference:  SJ 18114 43816

Summit Height:  259m

Drop Summit to Bwlch:  87m

Drop Bwlch to ODN:  172m 

Myrddyn Phillips (June 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Pt. 258m (SH 647 065) – Lesser Dominant addition (23rd reclassification)

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales which has resulted in this hill being added to the Lesser Welsh Dominant list.  The criteria for inclusion in this category of sub list is those Welsh P30 hills whose prominence is 33% or more and below 50% of their absolute height.

The details relating to this hill’s inclusion as a Lesser Welsh Dominant hill are retrospective as it appeared in the Tarennydd group of hills when published on the Mapping Mountains site on the 3rd December 2016.

The hill did not appear in the original listing of Y Trechol – The Dominant Hills of Wales as bwlch contours on Ordnance Survey maps of the day implied that the drop for the hill was only c 81m, with this based on the 258m summit spot height and an estimated bwlch height of 177m based on interpolation of bwlch contouring between 170m – 180m, these values would give the hill 31.40% Dominance which is insufficient for it to qualify for this sub list.

The hill is listed in the Tarennydd group and is placed in the Region of North Wales (Region A, Sub-Region A3) with its Cardinal Hill being Foel Wyllt (SH 624 042), and it is situated with the village of Abergynolwyn to its east and it rises above Dyffryn Dysynni and the Afon Dysynni which are to its north-west.

The hill is adjacent to Craig yr Aderyn (Bird’s Rock) and makes a good small circuit with its lower heighted neighbour, with both summits situated on designated open access land and public footpaths connecting with their summits from the valleys towards the north, west and east.

The hill is being listed under the point (Pt. 258m) notation as I do not know an appropriate name for it either from local enquiry or historical research, and it qualifies for Lesser Welsh Dominant status based on the 171m bwlch spot height that appears on the Ordnance Survey enlarged mapping hosted on the Geograph website, this when coupled with its 258m summit spot height gives the hill 87m of drop and 33.72% Dominance.

The full details for the hill are:

Group:  Tarennydd

Name:  Pt. 258m

Dominance:  33.72%

OS 1:50,000 map:  124

Summit Grid Reference:  SH 64705 06587

Summit Height:  258m

Drop Summit to Bwlch:  87m

Drop Bwlch to ODN:  171m 

Myrddyn Phillips (May 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Cefn (SH 721 004) – Lesser Dominant reclassified to Dominant (22nd reclassification)

Significant Height Revisions post for Cefn

Significant Name Changes post for Cefn

There has been a reclassification to the list of the Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill derived from detail on contemporary maps derived from Ordnance Survey data and subsequently confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Cefn (SH 721 004)

The criteria for the list that this reclassification applies to are:

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format.

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Cefn and this was derived from the Tithe map, and it is adjoined to the Tarren y Gesail group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and it is positioned with the A493 road to its north and the A487 road to its south, and has the town of Machynlleth towards the east.

After the original 100m height band of Welsh P30 hills published on Geoff Crowder’s v-g.me website were standardised and interpolated heights and drop values also included, this hill was listed with an estimated c 114m summit height, based on 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, with these values giving this hill an estimated c 55m of drop and 48.25% dominance.

Extract from the Ordnance Survey 1:25,000 Explorer map

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 119m summit spot height and when coupled with its 59m bwlch spot height, these values gave this hill 60m of drop and 50.42% dominance.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the confirmation of the reclassification of this hill from Lesser Dominant status is due to LIDAR analysis, 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, which is sufficient for Dominant status.    

The full details for the hill are:

Group:  Tarren y Gesail

Name:  Cefn

OS 1:50,000 map:  135

Summit Height:  118.2m (LIDAR)

Summit Grid Reference:  SH 72126 00402 (LIDAR)

Bwlch Height:  59.0m (LIDAR)

Bwlch Grid Reference:  SH 72569 00795 (LIDAR)

Drop:  59.2m (LIDAR)

Dominance:  50.08% (LIDAR)

Myrddyn Phillips (May 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Coed y Garth (SH 661 165) – Lesser Dominant addition (subsequently deleted) (21st reclassification)

Due to LIDAR analysis initially conducted by Chris Crocker and George Gradwell, and subsequently by Myrddyn Phillips, this hill has been deleted from the Lesser Dominant list as with 27.1m of drop it does not qualify.

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales which has resulted in the hill being added to the Lesser Welsh Dominant list.  The criteria for inclusion in this category of sub list is those P30 hills whose prominence is 33% or more and below 50% of their absolute height.

The details relating to this hill’s inclusion as a Lesser Welsh Dominant hill are retrospective as it appeared in the Cadair Idris group of hills when published on the Mapping Mountains site on the 3^rd November 2016.

The hill did not appear in the original listing of Y Trechol – The Dominant Hills of Wales as Ordnance Survey maps only gave the summit of the hill as having an uppermost ring contour of 80m, and with bwlch contouring between 50m – 60m the drop had been estimated as being below the minimum of 30m required for consideration for this list.

Since this list’s inception online mapping has improved and it is details on the Ordnance Survey enlarged mapping hosted on the Geograph website combined with the Harvey 1:25,000 Cadair Idris Superwalker map that has both bwlch and summit spot heights for this hill, with the former being 56m and the latter 87m, with these values giving 31m of drop and 35.63% Dominance.

The hill is listed in the Cadair Idris group and is placed in the Region of North Wales (Region A, Sub-Region A3) with its Cardinal Hill being Cadair Idris (SH 711 130), and it is situated between the small communities of Arthog to the south-west and Abergwynant to the east north-east.

As the hill is situated in conifer plantation a route to its summit may prove problematic, with access from the track that crosses its bwlch to the north-east possibly offering the quickest approach.

The name of the hill is Coed y Garth and it qualifies for Lesser Welsh Dominant status based on the 87m summit spot height on the Harvey 1:25,000 Cadair Idris Superwalker map and the 56m bwlch spot height on the Ordnance Survey enlarged mapping hosted on the Geograph website, with these values giving this hill 31m of drop and 35.63% Dominance.

   

The full details for the hill are:

Group:  Cadair Idris

Name:  Coed y Garth

Dominance:  35.63%

OS 1:50,000 map:  124

Summit Grid Reference:  SH 66100 16583

Summit Height:  87m

Drop Summit to Bwlch:  31m

Drop Bwlch to ODN:  56m

Myrddyn Phillips (May 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Ynys Glog (SH 596 398) - Dominant addition (20th reclassification)

Survey post for Ynys Glog

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales due to detail included on the Ordnance Survey enlarged mapping hosted on the Geograph website and which was first spotted by Aled Williams.  This has resulted in the hill being added to the Dominant list.  With the criteria for inclusion to this list being those Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

The details relating to this hill’s inclusion as a Dominant hill are retrospective as it was added to the list shortly after Aled first proposed it as a new P30 in February 2014, and later appeared in the Moelwynion group of Dominant hills when published on Mapping Mountains on the 25^th February 2016.

Prior to Aled proposing this hill as a new P30 and its subsequent inclusion as a Dominant hill, it was not classified as contouring on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map implied that the hill did not have the required minimum 30m of drop to be considered for P30 and Dominant status.

The hill is in the Moelwynion group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) and is situated between the towns of Porthmadog to the west south-west and Penrhyndeudraeth to the east south-east.

The hill is not on open access land and therefore permission to visit should be sought.  For those wishing to do so the ascent is through undergrowth next to stunted deciduous trees to a summit which is slightly laid back from a large drop to fields below.

The name of the hill is Ynys Glog, and it was included as a Dominant hill based on detail from the Ordnance Survey enlarged mapping hosted on the Geograph website which gives the hill a 42m summit spot height and bwlch contouring between 5 – 10m, with an estimated bwlch height of c 8m, these values gave the hill c 34m of drop and 80.95% Dominance.  The hill has subsequently been surveyed using the Trimble GeoXH 6000 resulting in a 40.6m (converted to OSGM15) summit height and a 7.9m (converted to OSGM15) bwlch height, giving this hill 32.7m of drop and 80.44% Dominance.

The full details for the hill are:

Group:  Moelwynion

Name:  Ynys Glog

Dominance:  80.44%

OS 1:50,000 map:  124

Summit Grid Reference:  SH 59647 39826

Summit Height:  40.6m (converted to OSGM15)

Drop Summit to Bwlch:  32.7m

Drop Bwlch to ODN:  7.9m (converted to OSGM15) 

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

For details on the survey that confirmed this hill’s Dominance

Myrddyn Phillips (April 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Ynys Berfedd (SH 599 398) - Dominant addition (19th reclassification)

Survey post for Ynys Berfedd

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales due to detail included on the Ordnance Survey enlarged mapping hosted on the Geograph website and which was first spotted by Aled Williams.  This has resulted in the hill being added to the Dominant list.  With the criteria for inclusion to this list being those Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

The details relating to this hill’s inclusion as a Dominant hill are retrospective as it was added to the list shortly after Aled first proposed it as a new P30 in February 2014, and later appeared in the Moelwynion group of Dominant hills when published on Mapping Mountains on the 25^th February 2016.

Prior to Aled proposing this hill as a new P30 and its subsequent inclusion as a Dominant hill, it was listed in the sub list that accompanied the Welsh P30 lists that were published on Geoff Crowder’s v-g.me website with a c 30m summit height, and not in the main P30 list as the contouring on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map implied that the hill did not have the required minimum 30m of drop to be considered for Dominant status.

The hill is in the Moelwynion group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) and is situated between the towns of Porthmadog to the west south-west and Penrhyndeudraeth to the south-east.

The hill is not on open access land and therefore permission to visit should be sought.  For those wishing to do so the ascent is next to stunted deciduous trees and on moss covered rocks to a summit overlooking a vertical drop to the north.

The name of the hill is Ynys Berfedd, and it was included as a Dominant hill based on detail from the Ordnance Survey enlarged mapping hosted on the Geograph website which gives the hill a 43m summit spot height and bwlch contouring between 0 – 10m, with an estimated bwlch height of c 6m, these values gave the hill c 37m of drop and 86.05% Dominance.  The hill has subsequently been surveyed using a Trimble GeoXH 6000 resulting in a 42.9m (converted to OSGM15) summit height and a 6.8m (converted to OSGM15) bwlch height, giving this hill 36.1m of drop and 84.06% Dominance.

The full details for the hill are:

Group:  Moelwynion

Name:  Ynys Berfedd

Dominance:  84.06%

OS 1:50,000 map:  124

Summit Grid Reference:  SH 59943 39865

Summit Height:  42.9 (converted to OSGM15)

Drop Summit to Bwlch:  36.1m

Drop Bwlch to ODN:  6.8m (converted to OSGM15) 

The Trimble GeoXH 6000 gathering data at the summit of Ynys Berfedd

For details on the survey that confirmed this hill’s Dominance

Myrddyn Phillips (April 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Ynys Gron (SH 596 392) - Dominant deletion (18th reclassification)

Survey post for Ynys Gron

There has been a deletion to the listing of Y Trechol – The Dominant Hills of Wales due to detail included on current Ordnance Survey maps.  This has resulted in the hill being taken out of the Dominant list.  With the criteria for inclusion to this list being those Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

The details relating to this hill’s deletion as a Dominant hill are retrospective as it did not appear in the Moelwynion group of hills when published on Mapping Mountains on the 25^th February 2016.

The hill had been listed in the original Welsh P30 lists when published on Geoff Crowder’s v-g.me website with a 96m summit height based on the Ordnance Survey 1:25,000 Outdoor Leisure spot height, with an accompanying note stating ‘98m on 1984 1:50,000 map.  Summit being reduced due to quarrying’.  When drop values were added to the P30 Master Lists this hill was given an estimated drop of c 50m which gave the hill 52.08% Dominance, and therefore it was included in the original listing of Y Trechol – The Dominant Hills of Wales.

The hill is in the Moelwynion group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) and is situated between the towns of Porthmadog to the west and Penrhyndeudraeth to the east, and immediately above the busy A 487 road which is to its south.

The hill is not on open access land and its whole south-western part forms the Garth Quarry, which is operational, because of this permission to visit should be sought.  However, the approach from the east is through woodland and would take a visitor direct to the remaining high point of the hill.

The name of the hill is Ynys Gron, which is a locally known name and it has been deleted from the Dominant list as the quarry has now obliterated the upper 30m of the hill and reduced it in height to 69.4m (converted to OSGM15), and as its bwlch has been surveyed as 44.3m (converted to OSGM15) in height, it gives this hill only 25.1m of drop, which is insufficient for it to be considered for Dominant status.

The full details for the hill are:

Group:  Moelwynion

Name:  Ynys Gron

Dominance:  N/A

OS 1:50,000 map:  124

Summit Grid Reference:  SH 59653 39268

Summit Height:  69.4m (converted to OSGM15)

Drop Summit to Bwlch:  25.1m

Drop Bwlch to ODN:  44.3m (converted to OSGM15) 

The view west from the summit of Ynys Gron

 For details on the survey that confirmed this hill’s lack of Dominance

Myrddyn Phillips (April 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Moel y Penmaen (SH 338 386) - Lesser Dominant addition (17th reclassification)

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales which has resulted in the hill being added to the Lesser Welsh Dominant list.  The criteria for inclusion in this category of sub list is those Welsh P30 hills whose prominence is 33% or more and below 50% of their absolute height.

The details relating to this hill’s inclusion as a Lesser Welsh Dominant hill are retrospective as it appeared in the Pen Llŷn group of hills when published on the Mapping Mountains site on the 11^th February 2016.

The hill did not appear in the original listing of Y Trechol – The Dominant Hills of Wales even though the details on the then current Ordnance Survey maps showed a 153m summit spot height and bwlch contours between 90m – 100m, with an estimated bwlch height of c 92m giving a drop of c 61m and a Dominance of 39.87% which is sufficient for inclusion into the Lesser Welsh Dominant list.

The hill is listed in the Pen Llŷn group and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Garn Ganol (SH 364 447), and it is situated between the small communities of Boduan to the south-west and Llannor to the south-east.

If wanting to visit the hill a track to the south-east which makes its way toward a small reservoir gives easy access to the upper part of the hill which is on open access land.

The name of the hill is Moel y Penmaen and it qualifies for Lesser Welsh Dominant status based on a 153m summit and a c 92m bwlch height, with these values giving this hill c 61m of drop and 39.87% of Dominance.

The full details for the hill are:

Group:  Pen Llŷn

Name:  Moel y Penmaen

Dominance:  39.87%

OS 1:50,000 map:  123

Summit Grid Reference:  SH 33810 38687

Summit Height:  153m

Drop Summit to Bwlch:  c 61m

Drop Bwlch to ODN:  c 92m 

Myrddyn Phillips (March 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Pt. c 71m (SH 310 297) - Lesser Dominant addition (subsequently deleted)(16th reclassification)

Due to LIDAR analysis reported by Chris Crocker, and subsequently conducted by Myrddyn Phillips, this hill has been deleted from the Lesser Dominant list as with 29.6m of drop it does not qualify.

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales due to detail included on the Ordnance Survey enlarged mapping hosted on the Geograph website.  This has resulted in the hill being added to the Lesser Welsh Dominant list.  The criteria for Lesser Welsh Dominant status is those P30 hills whose prominence is 33% or more and below 50% of their absolute height.

The details relating to this hill’s inclusion as a Lesser Welsh Dominant hill are retrospective as it appeared in the Pen Llŷn group of hills when published on the Mapping Mountains site on the 11^th February 2016.

Prior to this hill’s inclusion as a Lesser Welsh Dominant hill it was listed with c 25m of drop which is insufficient for consideration to this sub category of hill, with this drop value based on an estimated summit height of c 71m based on the size of the uppermost 70m ring contour on Ordnance Survey maps in comparison to the size of contours below it, and an estimated bwlch height of c 46m based on bwlch contouring between 40m – 50m that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps.   

The hill is listed in the Pen Llŷn group and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Garn Fadrun (SH 278 351), and it is situated between the small communities of Llanbedrog to the north-east, Mynytho to the north-west and Abersoch to the south.

If wanting to visit the hill permission to do so should be sought as the summit area is not a part of open access land, however the hill has a number of public footpaths encircling it that start from the A 499 road to its east and the network of minor roads to its north and west.

The hill is being listed by the point (Pt. c 71m) notation as an appropriate name either known locally or from historical research has not been found by the author, although when the hill was first included in the P30 Welsh lists that appeared on Geoff Crowder’s v-g.me website it was by an invented name of Castellmarch, this name was taken from buildings situated to the east of the summit.

It is included as a Lesser Welsh Dominant hill as the Ordnance Survey enlarged mapping hosted on the Geograph website has contours at 5m intervals giving the hill a 41m bwlch spot height with bwlch contouring between 40m – 45m, as opposed to the previously estimated bwlch height of c 46m based on the 40m – 50m bwlch contouring on the 1:25,000 Explorer map.  With an estimated c 71m summit height and a 41m bwlch height it gives this hill c 30m of drop which is sufficient for consideration to the Dominant list, and as these values give this hill 42.25% Dominance it is now listed as a Lesser Welsh Dominant hill.

The full details for the hill are:

Group:  Pen Llŷn

Name:  Pt. c 71m

Dominance:  42.25%

OS 1:50,000 map:  123

Summit Grid Reference:  SH 31034 29730

Summit Height:  c 71m

Drop Summit to Bwlch:  c 30m

Drop Bwlch to ODN:  41m 

Myrddyn Phillips (March 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Carreglefain (SH 324 410) - Lesser Dominant reclassified to Dominant (15th reclassification)

Survey post for Carreglefain

There has been a reclassification to the listing of Y Trechol – The Dominant Hills of Wales due to a survey with the Trimble GeoXH 6000.  This has resulted in the hill being reclassified from a Lesser Welsh Dominant to a Dominant hill.  With the criteria for inclusion to this list being those Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

The details relating to this hill’s inclusion as a Dominant hill are retrospective as it appeared in the Pen Llŷn group of hills when published on the Mapping Mountains site on the 11^th February 2016.

Prior to this hill’s inclusion as a Dominant hill it was listed as a Lesser Welsh Dominant hill with 48.66% Dominance based on its 261m summit spot height that appears on Ordnance Survey 1:25,000 Explorer maps and a c 127m drop based on bwlch contouring between 130m – 140m with an estimated bwlch height of c 134m.

The hill is listed in the Pen Llŷn group and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Garn Ganol (SH 278 351), and it is situated between the small communities of Nefyn towards the west and Llithfaen to the north-east.

If wanting to visit the hill it can be accessed from a number of directions via public footpaths that lead to open access land that takes in the supper section of the hill.

The name of the hill is Carreglefain and the Trimble survey that resulted in its reclassification was conducted by Myrddyn Phillips on the 24^th November 2014 resulting in a 260.7m (converted to OSGM15) summit height and a 130.1m (converted to OSGM15) bwlch height, with these values giving this hill 130.6m of drop and 50.08% of Dominance.

The full details for the hill are:

Group:  Pen Llŷn

Name:  Carreglefain

Dominance:  50.08%

OS 1:50,000 map:  123

Summit Grid Reference:  SH 32421 41054

Summit Height:  260.7m (converted to OSGM15)

Drop Summit to Bwlch:  130.6m

Drop Bwlch to ODN:  130.1m (converted to OSGM15) 

Carreglefain (SH 324 410) now reclassified from a Lesser Welsh Dominant to a Dominant hill

For details on the survey that reclassified this hill to Dominant status

Myrddyn Phillips (March 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Pt. 66m (SH 299 270) - Lesser Dominant reclassified to Dominant (14th reclassification)

There has been a reclassification to the listing of Y Trechol – The Dominant Hills of Wales due to detail included on the Ordnance Survey enlarged mapping hosted on the Geograph website.  This has resulted in the hill being reclassified from a Lesser Welsh Dominant to a Dominant hill.  With the criteria for inclusion to this list being those Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

The details relating to this hill’s inclusion as a Dominant hill are retrospective as it appeared in the Pen Llŷn group of hills when published on the Mapping Mountains site on the 11^th February 2016.

Prior to this hill’s inclusion as a Dominant hill it was included as a Lesser Welsh Dominant hill based on its summit position being at SH 295 266 where the 64m spot height appears on Ordnance Survey 1:25,000 Explorer maps, with its listed drop being c 31m based on an estimated bwlch height of c 33 and a Dominance of 48.44%, importantly this map showed a 60m ring contour to the north-east of this summit, but with no spot height the 64m map heighted summit was listed as the Lesser Welsh Dominant hill.

In more recent years the Ordnance Survey enlarged mapping hosted on the Geograph website has been made publicly available and this scale of mapping shows many spot heights not on any other publicly available map, and the 60m ring contour to the north-east of the 64m map heighted summit is given a 66m summit spot height on this more detailed and larger scaled map, and therefore the summit position of this hill has changed to the higher map heighted hill and because of this the drop value and Dominance of the hill has also altered, and it is now listed with a 66m summit and 32m bwlch height, with both spot heights taken from the enlarged map on the Geograph website.  These values give the hill 34m of drop and 51.52% Dominance.

The hill is in the Pen Llŷn group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Garn Fadrun (SH 278 351), and it is situated with the small community of Llanengan to the west and the small town of Abersoch to the north-east.

If wanting to visit the hill it can be easily ascended as it is near a number of minor roads, however its summit is not a part of open access land so permission to visit should be sought.

The hill is being listed by the point (Pt. 66m) notation as an appropriate name either known locally or from historical research has not been found by the author, although when the old summit was first listed in the sub list that accompanied the P30 Welsh lists that appeared on Geoff Crowder’s v-g.me website it was listed by an invented name of Bryn Llanengan, named after the village to the north-west of the old summit.

The hill is now listed with a 66m summit and 32m bwlch height, with both spot heights taken from the Ordnance Survey enlarged mapping hosted on the Geograph website.  These values give the hill 34m of drop and 51.52% Dominance.

The full details for the hill are:

Group:  Pen Llŷn

Name:  Pt. 66m

Dominance:  51.52%

OS 1:50,000 map:  123

Summit Grid Reference:  SH 29957 27041

Summit Height:  66m

Drop Summit to Bwlch:  34m

Drop Bwlch to ODN:  32m 

Myrddyn Phillips (March 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Carreg Rhoson (SM 672 256) - Dominant addition (13th reclassification)

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales due to detail included on the Ordnance Survey enlarged mapping hosted on the Geograph website.  This has resulted in the hill being added to the Dominant list.  With the criteria for inclusion to this list being those Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

The details relating to this hill’s inclusion as a Dominant hill are retrospective as it was added to the list shortly after its initial compilation was completed with the date of 31^st October 2012 given against its details.

Prior to this hill being listed as a P30 and its inclusion as a Dominant hill it had remained unclassified, as the uppermost 30m ring contour on the Ordnance Survey 1:25,000 Explorer map had not been spotted.

The hill is in the Pembrokeshire Islands group of hills and is placed in the Region of Mid and West Wales (Region B, Sub-Region B4) and is situated 5.175km from the nearest paved public road off the Pembrokeshire coast, and is positioned in the island chain of the Bishops and Clerks.

The name of the hill is Carreg Rhoson and this is also the name given to a number of adjacent islets, it is included as a Dominant hill as the Ordnance Survey enlarged mapping hosted on the Geograph website has greater scale and definition when compared to the smaller scaled and publicly available Ordnance Survey maps, and therefore its uppermost 30m ring contour is easier to see, and as this hill is also an island its c 30m summit height also gives it 100.00% Dominance.

The full details for the hill are:

Group:  Pembrokeshire Islands

Name:  Carreg Rhoson

Dominance:  100.00%

OS 1:50,000 map:  157

Summit Grid Reference:  SM 67235 25678

Summit Height:  c 30m

Drop Summit to Bwlch:  N/A

Drop Bwlch to ODN:  N/A 

The island chain of Carreg Rhoson with the new Dominant hill (SM 672 256) being the highest point on the right of this photograph

Myrddyn Phillips (March 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Castell Cricieth (SH 500 377) - Dominant addition (12th reclassification)

Survey post for Castell Cricieth

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales due to detail included on the Ordnance Survey enlarged mapping hosted on the Geograph website and which was first spotted by Alex Cameron.  This has resulted in the hill being added to the Dominant list.  With the criteria for inclusion to this list being those Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

The details relating to this hill’s inclusion as a Dominant hill are retrospective as it was added to the list shortly after Alex first proposed it as a new P30 in September 2014, and later appeared in the Moel Hebog group of hills when published on Mapping Mountains on the 28^th January 2016.

Prior to Alex Cameron proposing this hill as a new P30 and its subsequent inclusion as a Dominant hill it had remained unclassified, as the Ordnance Survey 1:50,000 Landranger map and 1:25,000 Explorer map has an uppermost contour of 30m and bwlch contouring between 10m – 20m, which implied that this hill did not have the required 30m of drop to be considered for Dominant status.

The hill is in the Moel Hebog group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) and is situated in the heartland of the town of Cricieth overlooking the sea, which is to its immediate east and south.

The name of the hill is taken from the castle at its top; Castell Cricieth,  and there is an admittance fee for those wishing to visit, it was included as a Dominant hill as the Ordnance Survey enlarged map hosted on the Geograph website has contours at 5m intervals giving the hill an uppermost contour of 45m and a summit spot height of 48m, with bwlch contouring between 15m – 20m, with an estimated bwlch of c 18m, giving the hill an estimated drop of c 30m and 62.5% Dominance.  The hill has subsequently been surveyed with the Trimble GeoXH 6000 with a summit height of 49.6m (converted to OSGM15) and a bwlch height of 19.3m (converted to OSGM15), with these values giving the hill 30.3m of drop and 61.02% Dominance.

The full details for the hill are:

Group:  Moel Hebog

Name:  Castell Cricieth

Dominance:  61.02%

OS 1:50,000 map:  123

Summit Grid Reference:  SH 50003 37733

Summit Height:  49.6m (converted to OSGM15)

Drop Summit to Bwlch:  30.3m

Drop Bwlch to ODN:  19.3m (converted to OSGM15) 

Castell Cricieth (SH 500 377) confirmed as a Dominant hill

For details on the survey that confirmed this hill’s Dominant status

Myrddyn Phillips (March 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Ynys Hir (SH 566 396) - Dominant addition (11th reclassification)

Survey post for Ynys Hir

Significant Height Revisions post for Ynys Hir

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales due to a survey with the Trimble GeoXH 6000.  This has resulted in the hill being added to the Dominant list.  With the criteria for inclusion to this list being those Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

The details relating to this hill’s inclusion as a Dominant hill are retrospective as it was surveyed on the 1^st February 2014 and later appeared in the Moel Hebog group of Dominant hills when published on the Mappingn Mountains site on the 28^th January 2016.

Prior to the survey with the Trimble this hill was unclassified as the Ordnance Survey 1:50,000 Landranger map, 1:25,000 Explorer map and the enlarged mapping hosted on the Geograph website all give the hill an uppermost 20m ring contour, implying that its height is not sufficient for P30 status and consideration as a Dominant hill.  However, it was Aled Williams who first proposed that this hill may attain P30 status and it was subsequently surveyed in his company.

The hill is in the Moel Hebog group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) and is situated between the communities of Porthmadog to its south and Tremadog to its north north-west, with the A 487 road to its immediate south.  The hill can be visited from this road where a lay-by gives access through a gate into the woodland that covers this and the other adjacent small hills.

The name of the hill is Ynys Hir and as its name implies it forms an island, which is now landlocked, it is included as a Dominant hill as the survey with the Trimble GeoXH 6000 produced a summit height of 37.3m, and with an estimated bwlch height of c 3m it gives this hill 91.21% Dominance.

The full details for the hill are:

Group:  Moel Hebog

Name:  Ynys Hir

Dominance:  91.21%

OS 1:50,000 map:  124

Summit Grid Reference:  SH 56695 39693

Summit Height:  37.3m (converted to OSGM15)

Drop Summit to Bwlch:  c 34m

Drop Bwlch to ODN:  c 3m 

Beyond the cliffs and immersed in woodland is the summit of Ynys Hir (SH 566 396) which is now classified as a Dominant hill

For details on the survey that confirmed this hill’s Dominant status

Myrddyn Phillips (February 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Dinas Dinlle (SH 436 564) - Dominant addition (10th reclassification)

Survey post for Dinas Dinlle

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales due to detail included on the Ordnance Survey enlarged mapping hosted on the Geograph website and which was first spotted by Chris Watson, and subsequently confirmed via a survey with the Trimble GeoXH 6000.  This has resulted in the hill being added to the Dominant list.  With the criteria for inclusion to this list being those Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

The details relating to this hill’s inclusion as a Dominant hill are retrospective as it was added to the list shortly after its initial compilation and later appeared in the Moel Hebog group of hills when published on Mapping Mountains on the 28^th January 2016.

Prior to Chris Watson raising the probability of this hill being a P30 and its subsequent inclusion as a Dominant hill it had remained unclassified, as the Ordnance Survey 1:50,000 Landranger map gave a 31m summit spot height and bwlch contouring between 0m – 10m, whilst the 1:25,000 Explorer map gave an uppermost 30m ring contour and the same bwlch contouring, which implied that the hill did not have the required 30m of drop to be considered for Dominant status.

The hill is positioned in the Moel Hebog group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) and is situated on the outskirts of the small community that takes its name from the hill; Dinas Dinlle, and is positioned with the sea to its immediate west which has eroded much of its slopes over recent years.  If wanting to visit the hill it can be easily accessed from the car park adjacent to the sea front from where a path heads up its northern slopes.

The name of the hill is Dinas Dinlle and as its name implies the upper section of the hill comprises an ancient hill fort, it was included as a 30-99m Twmpau as the Ordnance Survey enlarged mapping hosted on the Geograph website has contours at 5m intervals giving the hill an uppermost contour of 35m and bwlch contouring between 0m – 5m, these values give the hill an estimated drop of c 31m – c 32m.  The summit of this hill has subsequently been surveyed with the Trimble GeoXH 6000 as 34.7m (converted to OSGM15) and with a 4.1m bwlch height ascertained from LIDAR analyis, these values give this hill 30.6m of drop and 88.22% dominance. 

The full details for the hill are:

Group:  Moel Hebog

Name:  Dinas Dinlle

Dominance:  88.22%

OS 1:50,000 map:  115, 123

Summit Grid Reference:  SH 43676 56438

Summit Height:  34.7m (converted to OSGM15)

Drop Summit to Bwlch:  30.6m

Drop Bwlch to ODN:  4.1m

Dinas Dinlle (SH 436 564) now classified as a Dominant hill

For details on the survey that confirmed this hill’s Dominant status

Myrddyn Phillips (February 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Geirth Mawr (SH 535 393) - Dominant deletion (9th reclassification)

There has been confirmation of a deletion from the list of the Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data and confirmed from subsequent LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Geirth Mawr (SH 535 393)

The criteria for the list that this deletion applies to are:

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format.

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Geirth Mawr, and it is adjoined to the Moel Hebog group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A497 road to its north and minor roads to its west and east, and has the town of Porthmadog towards the east.

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.

Extract from the Ordnance Survey 1:25,000 Explorer map

Since the original publication of the Welsh P30 lists on Geoff Crowder’s v-g.me website there have been a number of maps made available online.  Some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website.  Whilst others were digitally updated such as the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map, whilst others are current and digitally updated such as the interactive mapping on the Magic Maps and WalkLakes websites.

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.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

Therefore, the confirmation of the deletion of this hill from Dominant status is due to LIDAR analysis, resulting in a 57.4m summit height and a 27.9m bwlch height, with these values giving this hill 29.5m of drop, which is insufficient for Dominant status.  

 

The full details for the hill are:

Group:  Moel Hebog

Name:  Geirth Mawr

OS 1:50,000 map:  124

Summit Height:  57.4m (LIDAR)

Summit Grid Reference:  SH 53511 39363 (LIDAR)

Bwlch Height:  27.9m (LIDAR)

Bwlch Grid Reference:  SH 53302 39651 & SH 53311 39649 (LIDAR)

Drop:  29.5m (LIDAR)

Dominance:  N/A (insufficient drop)

Myrddyn Phillips (February 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Coed Bodlondeb (SH 779 781) - Dominant addition (8th reclassification)

Survey post for Coed Bodlondeb

Significant Name Changes post for Coed Bodlondeb

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales due to detail included on the Ordnance Survey enlarged mapping hosted on the Geograph website.  This has resulted in the hill being added to the Dominant list.  With the criteria for inclusion to this list being those Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

The details relating to this hill’s inclusion as a Dominant hill are retrospective as it appeared in the Carneddau group of hills when published on Mapping Mountains on the 17th December 2015.

Prior to this hill’s inclusion as a Dominant hill it was listed with an estimated c 27m of drop based on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps giving the hill an uppermost 50m ring contour and bwlch contouring between 20m – 30m, resulting in an estimated summit height of c 53m and an estimated bwlch height of c 26m.

The hill is in the Carneddau group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) and is situated on the outskirts of Conwy with the Afon Conwy to its immediate north and east.

If wanting to visit the hill it can be accessed relatively easily with public parking available next to where the Offices are marked to the south of the summit on Ordnance Survey maps.  There are a number of paths marked on the map that head up to, or contour around the summit, and as the name of the hill suggests it is part of a wood which consists of deciduous trees.

The name of the hill is Coed Bodlondeb and it is included as a Dominant hill as the Ordnance Survey enlarged map hosted on the Geograph website has contours at 5m intervals giving the hill an uppermost contour of 55m and bwlch contouring between 20m – 25m.  Therefore the summit is estimated as being c 57m high and the bwlch estimated as being c 23m high, with these values giving this hill c 34m of drop and 59.65% Dominance.

Since this hill was originally included in the Y Trechol - The Dominant Hills of Wales list the summit has been surveyed with the Trimble GeoXH 6000 and the bwlch of the hill has been analysed via LIDAR and the resulting values are given below.

The full details for the hill are:

Cardinal Hill:  Tal y Fan

Name:  Coed Bodlondeb

OS 1:50,000 map:  115

Summit Height:  56.0m (converted to OSGM15)

Summit Grid Reference:  SH 77921 78114

Drop Summit to Bwlch:  33.0m (Trimble summit and LIDAR bwlch)

Drop Bwlch to ODN:  22.9m (LIDAR) 

Bwlch Grid Reference:  SH 77852 77725 (LIDAR)

Dominance:  59.01%

Gathering data at the summit of Coed Bodlondeb

For details on the summit survey of Coed Bodlondeb

Myrddyn Phillips (February 2017)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Mynydd Coch (SH 804 099) - Lesser Dominant deletion (7th reclassification)

Survey post for Mynydd Coch

Significant Name Changes post for Mynydd Coch


There has been a deletion from the listing of Y Trechol – The Dominant Hills of Wales due to a survey with the Trimble GeoXH 6000 and which has resulted in the hill being taken out of The Lesser Dominant Hills of Wales list and subjected to a life of rather pitiful non dominance.  The hill is in the group known as Bryniau Dyfi and is situated between the small communities of Aberllefenni to the west and Aberangell to the east, with the expanse of the Dyfi Forest enclosing the hill on its north, east and south.

The Trimble GeoXH 6000 survey that resulted in this hill’s deletion was conducted on the 13^th May 2015 in the company of Graham Jackson on a fine late spring day in clear and sunny conditions.

If wanting to visit the hill it can be accessed relatively quickly from its north-east where a forest track leaves the minor road that crosses these hills and makes its way toward the eastern face of Mynydd Coch and open countryside.  However, a more rewarding and extended walk starts from Aberllefenni with the path making its way to the summit through a deciduous wood and toward the 400m Sub-Pedwar of Foel Lwyd before the final ascent of the hill’s southerly upper slopes.

The name of the hill is Mynydd Coch and it had been listed with 33.48% Dominance which was based on its summit spot height of 469m and a bwlch spot height of 312m, with these values giving the hill 157m of drop.  The result of the Trimble GeoXH 6000 summit survey is 468.3m (468.298m, converted to OSGM15) and when coupled with this hill’s 312m map heighted bwlch gives this hill 156m of drop and only 33.31% Dominance, a smidgeon under the minimum qualifying percentage for Lesser Dominance.

The full details for the hill are:

Group:  Bryniau Dyfi

Name:  Mynydd Coch

Dominance:  33.31%

OS 1:50,000 map:  124, 125

Summit Grid Reference:  SH 80458 09952

Summit Height:  468.3m (converted to OSGM15)

Drop Summit to Bwlch:  156m

Drop Bwlch to ODN:  312m 

Mynydd Coch (SH 804 099) now deleted from the Lesser Welsh Dominants list

For details on the survey that resulted in this hill being demoted from the Lesser Welsh Dominant list please click {here}

Myrddyn Phillips (October 2016)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Foel Fawr (SM 705 225) - Lesser Dominant addition (6th reclassification)

Survey post for Foel Fawr


There has been a new entry in to the ranks of Y Trechol – The Dominant Hills of Wales due to a survey with the Trimble GeoXH 6000 and which has resulted in the hill being listed in The Lesser Dominant Hills of Wales list.  The hill is in the group known as the Pembrokeshire Islands and is situated on the southern part of Ynys Dewi, which is also commonly known as Ramsey.  This island is situated to the west of St David’s in the south-west of Wales.

The Trimble GeoXH 6000 survey that resulted in this hill’s reclassification was conducted on the 15^th May 2016 on a beautiful afternoon in still and sunny conditions.

As the hill is situated on an island the only way to approach is via boat and the only company with permission to land on Ynys Dewi is Thousand Island Adventures (tel: 01437-721721).  The hill can be easily accessed from where the boat docks as a gravelled track leads up to The Farmhouse from where a good path heads toward the southern part of the island.

The name of the hill is Foel Fawr and until the survey with the Trimble GeoXH 6000 the hill was listed with c 29m of drop, based on the 72m summit spot height on current Ordnance Survey maps, and an estimated bwlch height of c 43m based on bwlch contouring between 40m – 45m, with these values giving the hill c 29m of drop which is insufficient for qualification to the Y Trechol – The Dominant Hills of Wales list.

The survey with the Trimble GeoXH 6000 resulted in a 72.0m (71.954m, converted to OSGM15) summit height and a 41.9m (41.899m, converted to OSGM15)) bwlch height, with these values giving the hill 30.1m of drop and a Dominance of 41.77% which is sufficient for it to qualify as a Lesser Welsh Dominant hill.

The full details for the hill are:

Group:  Pembrokeshire Islands

Name:  Foel Fawr

Dominance:  41.77%

OS 1:50,000 map:  157

Summit Grid Reference:  SM 70542 22567

Summit Height:  72.0m (converted to OSGM15)

Drop Summit to Bwlch:  30.1m

Drop Bwlch to ODN:  41.9m (converted to OSGM15)  

Foel Fawr (SM 705 225) now classified as a Lesser Welsh Dominant

For details on the survey that resulted in this hill being classified as a Lesser Welsh Dominant

Myrddyn Phillips (May 2016)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Carn Ysgubor (SM 699 246) - Lesser Dominant reclassified to Dominant (5th reclassification)

Survey post for Carn Ysgubor


Please note; since this Hill Reclassifications post was announced the Ordnance Survey have adopted OSGM15, this remodelling has altered the known accurate height of Welsh hills be approximately 2-4cm, and the conversion to OSGM15 of data produced by the Trimble for Carn Ysgubor has resulted in this hill being reclassified back to the ranks of Lesser Dominant hills.


There has been a reclassification from the listing of Y Trechol – The Dominant Hills of Wales due to a survey with the Trimble GeoXH 6000 and which has resulted in the hill being taken out of The Lesser Welsh Dominant list and included in the Dominant list.  The hill is in the Group known as the Pembrokeshire Islands and is situated on the northern part of Ynys Dewi, which is also commonly known as Ramsey.  This island is situated to the west of St David’s in the south-west of Wales.

The Trimble GeoXH 6000 survey that resulted in this hill’s reclassification was conducted on the 15^th May 2016 on a beautiful morning in still and sunny conditions.

As the hill is situated on an island the only way to approach is via boat and the only company with permission to land on Ynys Dewi is Thousand Island Adventures (tel: 01437-721721).  The hill can be easily accessed from where the boat docks as a gravelled track leads up to The Farmhouse from where a vehicle path heads toward The Bungalow, which is a house on the eastern slopes of the hill.  A narrower path leaves this main route and heads toward the summit of the hill.

The name of the hill is Carn Ysgubor, with its composition presented as Carnysgubor on current Ordnance Survey maps, and it had been listed with 49.50% Dominance based on the 101m summit spot height on Ordnance Survey maps and an estimated bwlch height of c 51m, these values gave this hill c 50m of drop. 

The survey with the Trimble GeoXH 6000 resulted in a 102.4m (102.369m) summit height and a 51.2m (51.182m) bwlch height, giving this hill a Dominance of 50.00% (50.002442%) and therefore it just sneaks in to the ranks of being classified as a Dominant hill and confirms its reclassification from a Lesser Welsh Dominant to the ranks of Y Trechol - The Dominant Hills of Wales.

The full details for the hill are:

Group:  Pembrokeshire Islands

Name:  Carn Ysgubor

Dominance:  50.00%

OS 1:50,000 map:  157

Summit Grid Reference:  SM 69953 24603

Summit Height:  102.4m

Drop Summit to Bwlch:  51.2m

Drop Bwlch to ODN:  51.2m 

Carn Ysgubor (SM 699 246) now reclassified from a Lesser Welsh Dominant to a Dominant hill

For details on the survey that resulted in this hill being reclassified from a Lesser Welsh Dominant to a Dominant hill

Myrddyn Phillips (May 2016)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Ynys Fach (SM 822 327) - Dominant deletion (4th reclassification)

Survey post for Ynys Fach


There has been a deletion from the listing of Y Trechol – The Dominant Hills of Wales due to a survey with the Trimble GeoXH 6000 and which has resulted in the hill being taken out of the main Dominant list and subjected to a life of rather pitiful non dominance.  The hill is in the group known as the Pembrokeshire Islands and is situated on the northern coast of Pembrokeshire, and is positioned between the small communities of Trefin (Trevine) to its east and Porthgain to its west.

The hill is better described as an island, and even more so as a tidal island, as it is connected to the coastline of mainland Wales by a pebbled beach that according to maps is cut off from the mainland at high water.  It can be approached by boat, but an ascent of the island is feasible, albeit with a steep and potentially dangerous descent to the bwlch from the mainland.  This approach starts from directly opposite the island and necessitates finding a route down through scrub undergrowth and bi-passing the rock and cliffs that predominate this part of the coastline.  If attempting this route please be careful.

The Trimble GeoXH 6000 survey that resulted in this island’s deletion was conducted on the 14^th May 2016 on a beautiful sunny evening in the company of Adrian Rayner, Ayako and Rob Woodall.  It was Rob’s suggestion to go and have a look at it, and he found the route down to the pebbled beach which constitutes this island’s connecting bwlch.

The name of the island is Ynys Fach and it had been listed with 96.77% Dominance based on a summit height of c 31m estimated from the island having an uppermost 30m ring contour on current Ordnance Survey maps, and an estimated bwlch height of 1m taken to the pebbled beach connecting this island to the mainland.

Two points were surveyed for summit position and these are given below:

Summit 1:  30.8m (30.789m, converted to OSGM15) at SM 82209 32743

Summit 2:  30.7m (30.727m, converted to OSGM15) at SM 82217 32752

The data set for the bwlch was remarkably good when considering that the equipment was placed in what resembled an enclosed and walled canyon, with the resulting height being 1.2m (1.225m, converted to OSGM15) at SM 82180 32693.  These values give Ynys Fach a drop of only 29.6m which is below the minimum of 30m drop required for qualification to the Y Trechol – the Dominant Hills of Wales list.

The full details for the hill are:

Group:  Pembrokeshire Islands

Name:  Ynys Fach

Dominance:  N/A

OS 1:50,000 map:  157

Summit Grid Reference:  SM 82209 32743

Summit Height:  30.8m (converted to OSGM15)

Drop Summit to Bwlch:  29.6m

Drop Bwlch to ODN:  1.2m (converted to OSGM15)  

Ynys Fach (SM 822 327) now deleted from the ranks of Y Trechol - The Dominant Hills of Wales

For details on the survey that resulted in this hill being demoted from Y Trechol - The Dominant Hills of Wales

Myrddyn Phillips (May 2016)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Moel y Gadair (SH 521 391) - Lesser Dominant deletion (3rd reclassification)

Summit survey post for Moel y Gadair

Bwlch survey post for Moel y Gadair


This hill has subsequently been reinstated to Lesser Dominant status due to LIDAR analysis indicating this hill is a natural P30, with the raised road passing over the bwlch considered a relatively recent man-made construct; therefore it is excluded from the height of the bwlch. 

There has been a deletion from the listing of Y Trechol – The Dominant Hills of Wales due to a survey with the Trimble GeoXH 6000 and subsequent LIDAR analysis which has resulted in the hill being taken out of The Lesser Welsh Dominant list and subjected to a life of rather pitiful non dominance.

The hill is in positioned in the Moel Hebog group and is situated on the south-western outskirts of the small community of Pentrefelin, which is positioned between the towns of Porthmadog to its east and Cricieth to its south-west.

The Trimble GeoXH 6000 survey that resulted in this hill’s deletion was conducted over two days, with the hill’s summit being surveyed on the 15^th June 2015 in warm and sunny conditions, and the bwlch being surveyed on the 23^rd February 2016 on a beautiful winter’s day, with subsequent LIDAR analysis confirming the status of this hill.

If wanting to visit the hill it can be accessed from a public footpath to its south-west, but as its summit is not on open access land permission to visit its high point should be sought.

The name of the hill is Moel y Gadair and it had been listed with 45.05% dominance and a drop value of c 30m, with the latter figure the minimum required for qualification to the Dominant list.  These figures were based on a summit survey of 66.7m and an interpolated bwlch height of c 37m based on bwlch contouring between 35m – 40m.  During the 15^th June 2015 survey the contours at the bwlch were misinterpreted resulting in the second bwlch survey which was conducted on the 23^rd February 2016 and the subsequent LIDAR analysis resulting in a bwlch height of 36.8m.

Therefore, the deletion of this hill from Lesser Dominant status is due to a 66.7m summit height and a 36.8m bwlch height, with these values giving this hill 29.9m of drop which is insufficient for qualification to the Dominant list.


The full details for the hill are:

Group:  Moel Hebog

Name:  Moel y Gadair

Dominance:  N/A

OS 1:50,000 map:  124

Summit Grid Reference:  SH 52165 39135

Summit Height:  66.7m (converted to OSGM15)

Drop Summit to Bwlch:  29.9m

Drop Bwlch to ODN:  36.8m (LIDAR)  

The final nail in the coffin - the Trimble set-up position at the bwlch of Moel y Gadair (SH 521 391)  which resulted in this hill's deletion from the Lesser Dominant list

For details on the summit survey and the bwlch survey that resulted in this hill being deleted from Lesser Dominant status.

My thanks to Aled Williams for his initial LIDAR analysis

Myrddyn Phillips (February 2016)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Moelfre (SH 558 375) - Dominant reclassified to Lesser Dominant (2nd reclassification)

Survey post for Moelfre

Significant Name Changes post for Moelfre


There has been a reclassification from the listing of Y Trechol – The Dominant Hills of Wales due to a survey with the Trimble GeoXH 6000 and which has resulted in the hill being taken out of the Dominant list and included in the Lesser Welsh Dominant list.  The hill is in the Group known as Moel Hebog and is situated to the south-west of Porthmadog, overlooking the coast and above the small community of Borth-y-gest.

The Trimble GeoXH 6000 survey that resulted in this hill’s reclassification was conducted on the 23^rd February 2016 on a beautiful winter’s morning in sunny conditions.

The hill can be accessed from its west, east, south and north, with my two visits starting from the south and north respectively.  Access to mid-way up the hill can be gained via public footpaths but the high point is not on open access land, so permission to visit should be sought.

The hill remains unnamed on current Ordnance Survey maps but local enquiry with Aled Williams; a native of Porthmadog, confirms that the hill is known locally as Moelfre.

The hill had been listed with 50.00% of Dominance and was therefore included in the main Dominant list.  This was based on it having a 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, these values gave the hill a prominence of c 37m, which was enough for it to sneak into the main Dominant list.

The survey with the Trimble GeoXH 6000 resulted in a 74.1m (74.056m, converted to OSGM15) summit height and a 37.8m (37.770m, converted to OSGM15) bwlch height, giving this hill a Dominance of only 49.00% and confirming its reclassification from The Dominant Hills of Wales list to The Lesser Welsh Dominant list.

The full details for the hill are:

Group:  Moel Hebog

Name:  Moelfre

Dominance:  49.00%

OS 1:50,000 map:  124

Summit Grid Reference:  SH 55830 37553

Summit Height:  74.1m (converted to OSGM15)

Drop Summit to Bwlch:  36.3m

Drop Bwlch to ODN:  37.8m (converted to OSGM15)  

Moelfre (SH 558 375) now reclassified to the Lesser Welsh Dominant list

For details on the survey that resulted in this hill being reclassified to a Lesser Welsh Dominant hill please click {here}

Myrddyn Phillips (February 2016)

Mapping Mountains - Hill Reclassifications - Y Trechol - The Dominant Hills of Wales

Llanlleiana Park (SH 383 949) - Dominant reclassified to Lesser Dominant (1st reclassification)

Survey post for Llanlleiana Park

Significant Name Changes post for Llanlleiana Park

There has been a reclassification from the listing of Y Trechol – The Dominant Hills of Wales due to a survey with the Trimble GeoXH 6000 and which has resulted in the hill being taken out of the Dominant list and included in The Lesser Welsh Dominant list.  The hill is in the first Group to be published in this new hill list; Ynys Môn, and is situated on the northern coast of the island and positioned to the north-east of the small community of Cemaes.

This Hill Reclassifications notification has awaited the listing of Y Trechol – the Dominant Hills of Wales to begin its publication, but the survey result is retrospective as the Trimble GeoXH 6000 survey that resulted in this hill’s reclassification was conducted on the 7^th September 2014 on a beautiful sunny day in the company of Alex Cameron.

The hill can be accessed from its west or east via the Wales Coast Path which goes close to its summit, with its eastern approach on this path being joined by a public footpath that gives access toward the hill from its south-east.  However, if wanting a slightly extended walk this hill can be combined with its neighbours of Dinas Gynfor (SH 391 950) and Graig Wen (SH 397 947).

The hill is now listed by the name of Llanlleina Park, which was derived from the Tithe map and remains unnamed on contemporary Ordnance Survey maps. 

The hill had been listed with 50.75% of Dominance and was therefore included in the main Dominant list.  This was based on it having a 67m summit spot height on the Ordnance Survey enlarged mapping hosted on the Geograph website and an estimated bwlch height of c 33m based on bwlch contouring between 30m – 35m, these values gave the hill a prominence of c 34m, which was enough for it to sneak into the main Dominant list.

The survey with the Trimble GeoXH 6000 resulted in a 68.2m (converted to OSGM15) summit height and a 34.2m (converted to OSGM15) bwlch height, giving this hill a Dominance of only 49.85% and confirming its reclassification from The Dominant Hills of Wales list to The Lesser Welsh Dominant list.

The full details for the hill are:

Group:  Ynys Mon

Name:  Llanlleiana Park

Dominance:  49.85% (Lesser Welsh Dominant status confirmed)

OS 1:50,000 map:  114

Summit Grid Reference:  SH 38337 94993

Summit Height:  68.2m (converted to OSGM15)

Drop Summit to Bwlch:  34.0m

Drop Bwlch to ODN:  34.2m (converted to OSGM15)  

Llanlleiana Park (SH 383 949) now reclassified to the Lesser Welsh Dominant list.

For details on the survey that resulted in this hill being reclassified to a Lesser Welsh Dominant hill please click {here}

Myrddyn Phillips (December 2015)