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

Mynydd Pencarreg (SN 575 432) – Lesser Dominant deletion

There has been a deletion 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 a Trimble GeoXH 6000 summit survey conducted by Myrddyn Phillips and LIDAR bwlch analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips. 

The summit area of Mynydd Pencarreg (SN 575 432)

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 Mynydd Pencarreg and it is the highest point in its own grouping of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned with the B4337 road to its south-west and the A482 road to its north-east, and has the town of Llanbedr Pont Steffan (Lampeter) towards the north. 

Extract from the Ordnance Survey 1:50,000 Landranger map

After the original 400m 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 138m of drop, based on the 415m summit spot height adjoined to a triangulation pillar that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 277m bwlch height, based on interpolation of 10m contouring between 270m – 280m, with these values giving this hill 33.25% dominance. 

Extract from the Ordnance Survey 1:25,000 Explorer map showing the area of the bwlch

The summit of this hill was subsequently surveyed with the Trimble GeoXH 6000, resulting in a 414.9m height and with the bwlch having been analysed via 2m LIDAR, resulting in a 276.2m height, these values gave this hill 138.7m of drop and 33.43% domiance, which was sufficient for it to be classified as a Lesser Dominant hill. 

The Trimble GeoXH 6000 gathering data at the summit of Mynydd Pencarreg

However, it was not until the latest 1m 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 bwlch image of Mynydd Pencarreg

Therefore, the deletion of this hill from Lesser Dominant status is due to LIDAR bwlch analysis coupled with the summit height derived from the Trimble GeoXH 6000 survey, resulting in a 414.9m summit height and a 276.7m bwlch height, with these values giving this hill 138.2m of drop and 33.32% dominance, which is insufficient for Lesser Dominant status. 

 

The full details for the hill are:

Group:  Mynydd Pencarreg

Name:  Mynydd Pencarreg

OS 1:50,000 map:  146

Summit Height:  414.9m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 57560 43115 (Trimble GeoXH 6000)

Bwlch Height:  276.7m (LIDAR)

Bwlch Grid Reference:  SN 60000 44090 (LIDAR)

Drop:  138.2m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  33.32% (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

Myrddyn Phillips (July 2024)

 

 

 

 

  

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

THIS HILL HAS SUBSEQUENTLY BEEN DELETED FROM LESSER DOMINANT STATUS

Mynydd Pencarreg (SN 575 432) – Lesser Dominant addition

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales due to a combination of LIDAR analysis conducted by Aled Williams and a summit survey with the Trimble GeoXH 6000 conducted by Myrddyn Phillips, with the latter taking place on the 31^st July 2018.

The summit of Mynydd Pencarreg (SN 575 432)

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 addition Welsh P30 hills whose prominence is 33.33% or more and below 50% 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.

Prior to LIDAR analysis and the summit survey with the Trimble GeoXH 6000 this hill was listed with an estimated c 138m of drop based on the 415m summit height given to a triangulation pillar that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated bwlch height of c 277m based on interpolation of bwlch contouring between 270m – 280m on these two maps and partial 5m contouring that appears on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website, with these values giving this hill 33.25% dominance.

                               

The name of the hill is Mynydd Penycarreg and it is the highest hill in own grouping of hills, which are situated in the central part of Mid and West Wales (Region B, Sub-Region B2), and it is positioned between the B 4337 road to the south-west and the A 482 road towards the north-east, and has the town of Llanbedr Pont Steffan (Lampeter) towards the north.

As the summit of the hill is a part of designated open access land permission to visit does not have to be sought, however this open access land is almost an island without any public footpaths leading to it and with only one recognised access point from a minor road to the south-west of the summit.

The addition of Mynydd Pencarreg to Lesser Dominant status is due to LIDAR analysis conducted by Aled Williams coupled with a Trimble GeoXH 6000 summit survey conducted by Myrddyn Phillips.   The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

The survey with the Trimble produced a summit height of 414.9m (converted to OSGM15), whilst the LIDAR analysis produced a bwlch height of 276.2m, with these values giving this hill 138.7m of drop and 33.43% dominance, which confirms its addition to Lesser Dominant status.

The Trimble GeoXH 6000 gathering data at the summit of Mynydd Pencarreg

The full details for the hill are:

Group:  Mynydd Pencarreg

Name:  Mynydd Pencarreg

OS 1:50,000 map:  146

Summit Grid Reference:  SN 57560 43215

Summit Height:  414.9m (converted to OSGM15)

Bwlch Grid Reference:  SN 60011 44082 (LIDAR)

Drop Summit to Bwlch:  138.7m (Trimble summit and LIDAR bwlch)

Drop Bwlch to ODN:  276.2m (LIDAR)

Dominance:  33.43% (Trimble summit and LIDAR bwlch)

For details on the summit survey of this hill

Myrddyn Phillips (December 2018)

Mapping Mountains – Trimble Surveys – Mynydd Pencarreg

31.07.18  Mynydd Pencarreg (SN 575 432)

Mynydd Pencarreg (SN 575 432)

As I drove south toward Mynydd Pencarrag, the first hill of a planned twelve over two days and mainly in the vicinity of Caerfyrddin (Carmarthen), the dry roads around the northern part of mid Wales gave way to wet tarmac with muddied puddles beside their edges, there had been heavy overnight rain and the grey skies had not cleared as the further south-west I drove the murk heralded more rain.  I missed my turn off on the B4337 toward Llanybydder and this at least gave the hills another unplanned 30 minutes to clear their tops of drizzled murk.

Access to Mynydd Pencarreg is easy if choosing the end of the minor lane to the south-east of the summit that gives access to the large mast in the adjacent field.  This is a transmitting station which incorporates a 99m (325ft) high mast, and provides digital television and FM radio to the Lampeter area.

By the time I parked my car and tied up my walking boots the skies directly overhead were free of wet murk, but all around looked forbiddingly bleak as heavy dark grey cloud sped in from the west, with the western coastal regions looking decidedly grey with no doubt lots of rain.

I used the access track to the transmitter mast hoping this would lead direct to the high point of the hill, I suspect it does via a gate, but I doubled back to gain access to a field where the trig pillar at the summit was now in view.

It was only a short walk to the trig pillar and the erratic boulder placed a few metres away which is taken as the summit of the hill, this stood out from afar and it soon had the Trimble perched on its high point gathering the allotted data.

Gathering data at the summit of Mynydd Pencarreg

The Trimble set-up position at the summit of Mynydd Pencarreg

When data were being gathered I headed further north-west in to the adjacent field to visit its high point and look back at the trig, boulder and mast, and take photos as dark cloud zoomed overhead interspersed with flashes of sunlight.  Away to the south-west was the next hill I planned to visit; Mynydd Llanybydder and this again was battling with darkened murky cloud interspersed with occasional flashes of sunlight.

The high transmitting mast near the summit of Mynydd Pencarrag

Dark clouds massing as the Trimble gathers data

By the time seven minutes of data were gathered and stored the murk was heading my way, so I quickly packed the Trimble away and left the hill down a field and took a line straight toward my car, as I arrived the first drops of rain were falling and Mynydd Llanybydder was now immersed in wet clag with its forested slopes looking decidedly uninviting.

Survey Result:

Mynydd Pencarreg

Summit Height:  414.9m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 57560 43215 (Trimble GeoXH 6000)

Bwlch Height:  276.7m (LIDAR)

Bwlch Grid Reference:  SN 60000 44090 (LIDAR)

Drop:  138.2m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  33.32% (Trimble GeoXH 6000 summit and LIDAR bwlch) (Lesser Dominant addition) (Lesser Dominant deletion) 

For further details please consult the Trimble Survey Spreadsheet