Mapping Mountains – Hill Reclassifications – Y Pedwarau – The 400m Hills of Wales

 

Crug Siarls (SN 702 483) – 390m Sub-Pedwar deletion

There has been a deletion from the listing of the Y Pedwarau – The 400m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Crug Siarls (SN 702 483)

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

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are five categories of sub hills, with this hill being deleted from the 390m Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 390m and below 400m in height that have 30m minimum drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Crug Siarls, and it is adjoined to the Esgair Wen 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 west and south, the B4343 road farther to its west, and the A482 road farther to its south-west, and has the town of Llanbedr Pont Steffan (Lampeter) towards the west.

When the original 300m height band of Welsh P30 hills compiled by Myrddyn Phillips was published on Geoff Crowder’s v-g.me website, this hill was included in the main P30 list with a 391m summit height, based on the 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

After 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 54m of drop, based on the 391m summit spot height and the 337m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map, and these are the details giiven the hill when the 1^st edition of the Y Pedwarau, now co-authored by Myrddyn Phillips and Aled Williams was published by Europeaklist in May 2013.

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 deletion of this hill from 390m Sub-Pedwar status is due to LIDAR analysis, resulting in a 389.7m summit height and a 336.8m bwlch height, with these values giving this hill 52.9m of drop, with the summit height insufficient for it to be classified as a 390m Sub-Pedwar.                                         

 

The full details for the hill are:

Group:  Esgair Wen

Name:  Crug Sials

OS 1:50,000 map:  146, 147

Summit Height:  389.7m (LIDAR)

Summit Grid Reference:  SN 70220 48343 (LIDAR)

Bwlch Height:  336.8m (LIDAR)

Bwlch Grid Reference:  SN 69635 48220 (LIDAR)   

Drop:  52.9m (LIDAR) 

 

For the additions, reclassifications and deletions to Y Pedwarau – The 400m Hills of Wales reported on Mapping Mountains since the May 2013 publication of the list by Europeaklist please consult the following Change Registers:

 

Y Pedwarau

 

Y Pedwarau – 400m Sub-Pedwarau

 

Y Pedwarau – 390m Sub-Pedwarau

 

Y Pedwarau – 390m Double Sub-Pedwarau

 

Myrddyn Phillips and Aled Williams (February 2026) 

Monthly Synopsis

 

Synopsis of all major changes detailed on Mapping Mountains during the last calendar month.  These can include new, confirmation and retrospective changes

 

Hill Reclassifications: 

Hafod Las (SN 738 506) - Trichant reinstatement

Harpur Hill Quarry (SK 066 707) - Sub-Four addition

Carreg Rhoson (SM 666 254) - 30-99m Double Sub-Twmpau addition

 

Significant Height Revisions: 

Chwarel Penrhyn (SH 621 658) - 200m Twmpau

Summit Relocations: 

Yarnspath Law (NT 887 135) - Deweys

Ffridd Cadwaladr (SH 810 660) - The Welsh P15s

Burton How (NZ 607 032) - The Fours - The 400m Hills of England

Significant Name Changes: 

Ffridd Defaid (SN 663 983) - 100m Twmpau

Ffridd Cadwaladr (SH 810 660) - The Welsh P15s

Mapping Mountains – Significant Name Changes – The Welsh P15s

 

Ffridd Cadwaladr (SH 810 660) 

There has been a Significant Name Change to a hill that is listed in The Welsh P15s, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Ffridd Cadwaladr (SH 810 660)

The criteria for the list that this name change applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The hill is adjoined to the Mynydd Hiraethog group of hills, which are situated in the northern part of North Wales (Region A, Sub-Region A2), and it is positioned encircled by minor roads with the A470 road farther to its west and the A548 road farther to its south and the B5113 road farther to its east, and has the town of Llanrwst towards the south south-west.

When the listing that became known as The Welsh P15s was being compiled, this hill was listed under the point (Pt. 216m) notation, with 19m of drop, based on the 216m summit spot height and the 197m bwlch spot height that appear on the Ordnance Survey 1:25,000 Explorer map. 

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

As the summit of this hill comprises bounded land the details for it were examined on the Tithe map.  The term Tithe map is generally given to a map of a Welsh or English parish or township and which was prepared after the 1836 Tithe Commutation Act.  This act allowed tithes to be paid in cash rather than goods.  The Tithe maps gave names of owners and occupiers of land in each parish and importantly for place-name research they also included the name of enclosed land.  This enclosed land is usually based on a field system, however not every field is given a name, but many are and especially so in Wales. 

Extract from the Tithe map

The enclosed land where the summit of this hill is situated is given the number 184 on the Tithe map, this can be cross referenced against the apportionments; it is these apportionments that give the name of the owner or occupier of the land as well as the name of the land.  The land where the summit of this hill is situated is named Ffridd Cadwaladr in the apportionments, with the details on the Tithe map appearing in the parish named as Eglwys-fach and in the county named as Caernarfon. 

Extract from the apportionments

Therefore, the name this hill is now listed by in the The Welsh P15s is Ffridd Cadwaladr, and this was derived from the Tithe map. 

 

The full details for the hill are: 

Group:  Mynydd Hiraethog 

Name:  Ffridd Cadwaladr 

Previously Listed Name:  Pt. 216m 

OS 1:50,000 map:  116

Summit Height:  215.7m (LIDAR)                                                           

Summit Grid Reference:  SH 81092 66027 (LIDAR)                                                  

Bwlch Height:  198.3m (LIDAR) 

Bwlch Grid Reference:  SH 81357 65646 (LIDAR) 

Drop:  17.4m (LIDAR) 

 

Myrddyn Phillips (January 2026)

Mapping Mountains – Significant Height Revisions – 200m Twmpau

Chwarel Penrhyn (SH 621 658) 

There has been a Significant Height Revision to a hill that is listed in the 200m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Chwarel Penrhyn (SH 621 658)

The criteria for the list that this height revision applies to are:

200m Twmpau – Welsh hills at or above 200m and below 300m in height that have 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

200m Twmpau by Myrddyn Phillips

The name the hill is listed by is Chwarel Penrhyn, and it is adjoined to the Glyder Fawr 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 B4409 road to its north, a minor road to its west and the A5 road to its east, and has the town of Bethesda towards the north-east.

When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the accompanying Hills to be surveyed sub list, as with no significant contours of note on the contemporary Ordnance Survey 1:25,000 map, it was hard to know whether any hill with qualifying prominence existed and therefore it was considered not to meet the criteria then used for this sub category. 

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

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 summit image of Chwarel Penrhyn (SH 621 658)

LIDAR analysis gives the summit of this hill as 220.6m positioned at SH 62149 65875, and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey, Harvey or other interactive map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR.  Also included are hills whose summit map data is missing an uppermost ring contour when compared with the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 220.6m and this was derived from LIDAR analysis, this is 70.6m higher than the highest contour in the vicinity of this hill that appears on the contemporary Ordnance Survey 1:25,000 Explorer map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Glyder Fawr 

Name:  Chwarel Penrhyn 

OS 1:50,000 map:  115

Summit Height (New Height):  220.6m (LIDAR) 

Summit Grid Reference:  SH 62149 65875 (LIDAR) 

Bwlch Height:  197.0m (LIDAR) 

Bwlch Grid Reference:  SH 61793 65966 (LIDAR) 

Drop:  23.6m (LIDAR)

Myrddyn Phillips (January 2026) 

Mapping Mountains – Trimble Surveys – Arenig Fawr

13.12.25  Ffridd Trawsgoed (SH 837 328) and Moel Hafod yr Ŵyn (SH 841 322) 

Moel Hafod yr Ŵyn (SH 841 322)

There is bleak beauty in venturing on to rough, unremitting ground and especially so during the onset of winter where grey skies predominate and a brisk wind echoes across the land.

Today we visited two hills positioned just west of the southern most part of Llyn Tegid.  Both are relatively easy to access from the narrow road that winds its way across these hills toward Bronaber.  I hadn’t been on this road in many years and had not until today visited these two hills.

I met Mark and Aled in Y Bala, where we left two cars and then continued on the A494 road heading south-west beside the lake toward the minor road that in time would take us to our designated parking spot on a grass verge beside an old metal gate. 

Heading toward the forest track

The forecast gave south-westerly winds, so not chilled and relatively mild for the time of year.  I set off before Mark and Aled, but soon stopped and waited as the continuation of the way up the hill was indistinct with slender long grasses amongst bracken and stunted trees giving little indication of a path.  However, one did exist and once on it I followed my companions up to a forest track that shortly afterward bisected another track where a person was standing beside a gate.  As we approached we said hello; Andrew Graham was the landowner, his sister was standing a short distance further down the track.  We chatted for five minutes or so, he was concerned as the gate had been left open and wondered who had done it.  He’d come to the area in the 1960s having bought the land to turn it over to the conifer plantation that now surrounded us. 

Andrew Graham

As Andrew walked down the track to join his sister, we headed in the opposite direction looking for a convenient access point on to the upper hill, which now rose in front of us a mass of heather and roughness.  The going uphill from this point was steep and ponderous with no semblance of path.  It was hard work, but also a marvelous place to find oneself on a Saturday afternoon in December. 

The steep heathery slopes leading to the summit of Ffridd Trawsgoed

I arrived on top last out of the three and was immediately buffeted by the brisk wind.  Although I’d brought the Trimble I had little intention of using it unless the tops were covered in clag and then only as a hand-held GPS device.  However, I still placed it on the high point for the customary photograph. 

The summit of Ffridd Trawsgoed

To our south Moel Hafod yr Ŵyn looked a wild inviting hill, with a rather unpleasant bog between us and it.  Leaving the summit we stumbled our way down the steep pathless slope and back on to the relative comfort of the forest track.  However, the comfort didn’t last long as soon the bog would have to be tackled. 

Moel Hafod yr Ŵyn and its unsavoury looking bog

There’s a pleasing aspect to bogs.  Many are lush with copious amounts of undergrowth and this one was definitely one to savour.  Progress through it was never difficult and wearing vibram soled wellies certainly helped.  I followed Aled as he furrowed his way through, only stopping occasionally to regather my breath during which I looked at the slender threads of long grasses as they gently danced in the wind.  As I said; there is beauty in a bog. 

Mark tackling the bog

Mark soon joined us on the other side of the bog and as Aled headed up to gain height, Mark continued flanking the upper hill on the periphery of the bog before then heading up toward the summit cone.  Oh decisions decisions, what one to follow?  I opted for Aled and was soon being left behind as I made slow progress through the undergrowth.  By the time I spotted Mark he had gained height and was approaching the upper part of the hill, Aled was already nearing the summit.  I continued my slow plod up in to the realms of wind and views.

Aled heading toward the summit of Moel Hafod yr Ŵyn

The upper cone of Moel Hafod yr Ŵyn

The upper hill proved a delight with a small rock band to veer past.  Having reached the summit I did as I had done on top of Ffridd Trawsgoed and placed the Trimble on the high point for its customary photograph.  The view compensated for my tiredness, with the land to the west a wild and remote place of more tussocks, bog and rising hills, whilst to our south-east the descending slopes headed down to the gentler climes of the valley below. 

The summit of Moel Hafod yr Ŵyn

Leaving the high point I followed Aled down through mixed ground of heather and intermittent hidden rock.  Our route down led to a wall which had a barb wired fence perched menacingly on top of it.  This was not good news for the two elderly gentlemen in our walking party.  However, with the help of our younger colleague there was no mishap and soon we were standing on relatively safe ground on the other side. 

The last steep slope leading back on to the narrow road and the car parked beyond

From here it was only a short walk back to the car; with an initial steep slope leading on to the narrow road where we veered right and followed the thin width of tarmac a few hundred metres back to where we had started our walk from.

We were back in Y Bala at around 4.40pm and soon happily seated in the Plan yn Dre for an early evening festive meal, which proved an excellent way to end another good day on the hill. 

 

Survey Result: 

 

Ffridd Trawsgoed 

Summit Height:  423.9m (LIDAR)  

Summit Grid Reference:  SH 83755 32841 (LIDAR)

Bwlch Height:  384.2m (LIDAR)

Bwlch Grid Reference:  SH 83731 33086 (LIDAR) 

Drop:  39.7m (LIDAR)

Dominance:  9.36% (LIDAR)

 

 

Moel Hafod yr Ŵyn 

Summit Height:  398.2m (LIDAR) (significant height revision)  

Summit Grid Reference:  SH 84199 32238 (LIDAR)

Bwlch Height:  358.4m (LIDAR)

Bwlch Grid Reference:  SH 84033 32465 (LIDAR) 

Drop:  39.8m (LIDAR)

Dominance:  9.99% (LIDAR)

 

 

For further details please consult the Trimble Survey Spreadsheet