Mapping Mountains – Significant Height Revisions – Y Trichant – The 300m Hills of Wales

 

Craig y Bwlch (SN 718 696) 

There has been a Significant Height Revision to a hill that is listed in the Y Trichant – The 300m 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 Craig y Bwlch (SN 718 696)

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

Y Trichant – The 300m Hills of Wales – Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant, with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13^th May 2017, and the Introduction to the Mapping Mountains publication of the list appearing on the 1^st January 2022. 

Y Trichant - The 300m Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Craig y Bwlch, and it is adjoined to the Carn yr Hyrddod group of hills, which are situated in the northern part of South Wales (Region B, Sub-Region B1), and it is positioned with the B4340 road to its west, a minor road to its south-east and the B4343 road to its east, and has the village of Ysbyty Ystwyth towards the north-east.

When the original 300m 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, with an accompanying note stating; Automatically qualified until the top was quarried away.  350c on 1986 1:50000 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 an estimated c 27m of drop, based on an estimated c 342m summit height and an estimated c 315m bwlch height, with both heights based on interpolation of 10m contouring that appears on the Ordnance Survey 1:25,000 Explorer map. 

Extract from the interactive mapping hosted on the WalkLakes website which has a better portrayal of contours and the height of this hill

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 Craig y Bwlch (SN 718 696)

The summit height produced by LIDAR analysis is 350.3m and is positioned at SN 71860 69685, 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 or Harvey 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 to the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 350.3m and this was derived from LIDAR analysis, this is 8.3m higher than the previously listed summit height of c 342m, which was based on interpolation of the uppermost 340m ring contour on the contemporary Ordnance Survey 1:25,000 Explorer map. 

 

The full details for the hill are: 

Group:  Carn yr Hyrddod 

Name:  Craig y Bwlch 

OS 1:50,000 map:  135, 147

Summit Height (New Height):  350.3m (LIDAR)                                                           

Summit Grid Reference:  SN 71860 69685 (LIDAR) 

Bwlch Height:  312.0m (LIDAR) 

Bwlch Grid Reference:  SN 71462 69797 (LIDAR) 

Drop:  38.3m (LIDAR) 

 

Myrddyn Phillips (October 2023)

 

 

 

Mapping Mountains – Hill Reclassifications – Y Trichant – The 300m Hills of Wales

Craig y Bwlch (SN 718 696) – Sub-Trichant reclassified to Trichant

There has been a reclassification to the list of Y Trichant – The 300m 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 Craig y Bwlch (SN 718 696)

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

Y Trichant – The 300m Hills of Wales – Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant, with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13^th May 2017, and the Introduction to the Mapping Mountains publication of the list appearing on the 1^st January 2022. 

Y Trichant - The 300m Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Craig y Bwlch, and it is adjoined to the Carn yr Hyrddod group of hills, which are situated in the northern part of South Wales (Region B, Sub-Region B1), and it is positioned with the B4340 road to its west, a minor road to its south-east and the B4343 road to its east, and has the village of Ysbyty Ystwyth towards the north-east.

When the original 300m 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, with an accompanying note stating; Automatically qualified until the top was quarried away.  350c on 1986 1:50000 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 an estimated c 27m of drop, based on an estimated c 342m summit height and an estimated c 315m bwlch height, with both heights based on interpolation of 10m contouring that appears on 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.

Therefore, the reclassification of this hill from Sub-Trichant status is due to LIDAR analysis, resulting in a 350.3m summit height and a 312.0m bwlch height, with these values giving this hill 38.3m of drop, which is sufficient for it to be classified as a Trichant. 

 

The full details for the hill are: 

Group:  Carn yr Hyrddod 

Name:  Craig y Bwlch 

OS 1:50,000 map:  135, 147

Summit Height:  350.3m (LIDAR)                                                           

Summit Grid Reference:  SN 71860 69685 (LIDAR) 

Bwlch Height:  312.0m (LIDAR) 

Bwlch Grid Reference:  SN 71462 69797 (LIDAR) 

Drop:  38.3m (LIDAR) 

 

Myrddyn Phillips (October 2023)

 

 

 

 

 

  

Mapping Mountains – Trimble Surveys – Cymoedd Gwent

25.08.18  Craig y Bwlch (SN 942 035) and Tarren y Bwlch (SN 948 033)  

Tarren y Bwlch (SN 948 033)

The hills of the Cymoedd would not be in my top ten list of hill groups to revisit, partly due to the travelling distance from where I live, but also coupled with the fact that they have undergone dramatic change in the last 80 years with many now forested and in later years the profusion of wind farms have also impacted upon this land, and yet the hills themselves have a softness to the eye and must at one time have been part of a beautiful landscape that was farm managed and open.

However, along with Mark and Aled we were now heading south to their forested slopes, planning at least three walks with an option of a Pedwar tagged on at the end of the day if time permitted.

Our first hills were Craig y Bwlch and Tarren y Bwlch, these are situated overlooking the black debris of an opencast mine to their north, however they have extensive views from their summits and all except for their south-western slopes that connect with Mynydd Ystradffernol are free of conifer plantation and wind turbines.

I’d visited the higher of these hills twice before, and the lower Tarren y Bwlch on one occasion, each time using the convenience of a large lay-by on the A 4061 road to park my car with the prospect of a relatively quick and easy direct ascent to their summits.  This proved otherwise as the underfoot conditions consist of mounds of grassed tussocks, therefore today we opted to follow an ATV track bi-passing the worst of the copious amounts of tussock grass hoping it would lead around the northern escarpment edge toward the summit of Craig y Bwlch.

By the time we’d stopped for coffee and breakfast on our way south it was 12.00 midday when we set off walking down the road toward open hillside and the ATV track, this lost a little height when crossing one of the upper tributaries of the Nant Gwrangon and continued swinging north and then east around the escarpment edge of the hill, it was a pleasure to walk on the ATV track having previously experienced the rough going of a direct ascent.

Crossing one of the upper tributaries of the Nant Gwrangon

To our west the upper reaches of Craig y Llyn gleamed back as occasional flashes of sunlight struck its steep northern slopes, whilst away to our east the distinctive profile of the Beacons were free of cloud.  I’d come prepared with a series of ten figure grid references for the two summits and connecting bwlch, with one of these produced from Aled’s LIDAR analysis.

Craig y Llyn (SN 906 031)

The ATV track led toward a fence and continued up beside it to an access gate and then beyond toward the summit of Craig y Bwlch, after setting the Trimble up Mark and Aled sauntered off to have a bite to eat leaving me to wait for the allotted data to be gathered, during this a couple appeared walking on the track heading my way, they stopped and we chatted; Nick Hadfield and Marie-Andree Lachapelle had met when trekking the Inca Trail, and Marie-Andree had then moved from Canada to be with Nick, they are now married and enjoying the Welsh hills.  Nick used to be a surveyor working for a number of local mines and was one of the people who had surveyed these hills for the installation of a shaft, and therefore he was interested in the Trimble and my activities around the hills.

Gathering data at the summit of Craig y Bwlch

Marie-Andree and Nick

Once the Trimble had collected its allotted data I closed it down and joined Mark and Aled for the short walk east to the connecting bwlch with Tarren y Bwlch, I’d surveyed this hill for drop with my old basic levelling staff in August 2005 and today I had the opportunity to do likewise with the Trimble, and when doing so also give the hill an accurate summit and bwlch height.

Heading toward Tarren y Bwlch

Tarren y Bwlch (SN 948 033)

Mark assessed the lay of land at the bwlch and chose the spot for Trimble placement, and as it beeped away gathering its all-important data he and Aled headed toward the summit to sit near the northern escarpment enjoying the sunshine and views as first bwlch data and then summit data were gathered and stored.

Gathering data at the critical bwlch of Tarren y Bwlch

The Trimble set-up position at the summit of Tarren y Bwlch

Our inward route was also our outward, and once summit data were gathered the Trimble was packed away and we retraced our way back on the ATV track to the main road and the large lay-by which was now packed to busting with cars and people. 

Craig y Bwlch (SN 942 035)

Unbeknownst to us we had arrived to see the mountain top finish to the second stage of the SD Sealants Junior Tour of Wales 2018, and as we enjoyed our well-earned ice creams the first cyclists sped up the road to cheers from the numerous onlookers.

Our timing was perfect as by the time we were ready to leave the peloton had passed and the day’s cycle stage was over, next stop Mynydd Ystradffernol.

Survey Result:

Craig y Bwlch

  

Summit Height:  514.2m (converted to OSGM15)

Summit Grid Reference:  SN 94270 03503

Drop:  37m

Dominance:  7.23%

Tarren y Bwlch

Summit Height:  513.5m (converted to OSGM15)

Summit Grid Reference:  SN 94892 03392

Bwlch Height:  497.8m (converted to OSGM15)

Bwlch Grid Reference:  SN 94683 03320

Drop:  15.6m (Uchaf status confirmed)

Dominance:  3.04%

For further details please consult the Trimble Survey Spreadsheet