Mapping Mountains – Summit Relocations – Y Pedwarau

Mynydd Llanybydder (SN 535 395)

There has been a Summit Relocation to a hill that is listed in the Y Pedwarau, with the summit height, position and relocation confirmed by LIDAR analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips.

LIDAR image of Mynydd Llanybydder

The criteria for the list this summit relocation affects are:

Y Pedwarau - Welsh hills at or above 400m and below 500m in height that have 30m minimum drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and the Introduction to the Mapping Mountains publication of this list appeared on the 30^th January 2017. 

The name of the hill is Mynydd Llanybydder it is situated in the Mynydd Pencarreg range of hills, which are positioned in the central part of Mid and West Wales (Region B, Sub-Region B2), and it is positioned with the A 485 road to the west and the B 4337 road to the north-east, and has the town of Llanybydder towards the north north-west.

As the summit of the hill is a part of designated open access land it can in theory be approached from a number of directions, with the easiest via the access track to the high mast which is positioned adjacent to the summit area of this hill.  However, the summit of this hill is now located in a conifer plantation, thankfully its high point is not difficult to reach.

The summit area of this hill has a conifer plantation on its north-eastern side and open hillside on its south-western side, with the latter having an ancient tumulus on it with a triangulation pillar positioned near its high point which is given a 408.617m flush bracket height in the OS Trig Database.  Prior to LIDAR analysis it is this 408m map heighted position that was given as that for the summit in the 1^st edition of Y Pedwarau published by Europeaklist in May 2013.

Extract from the Ordnance Survey 1:25,000 Explorer map showing the summit position in relation to where the trig pillar and ancient tumulus is positioned

LIDAR summit image showing the ancient tumulus just below and to left of centre and the LIDAR summit just above and to right of centre

The Trimble GeoXH 6000 gathering data at the highest ground on top of the ancient tumulus

The LIDAR (Light Detection & Ranging) technique is highly accurate height data that is now freely available for much of England and Wales, and the area of the summit was analysed via LIDAR initially by Aled Williams and then by Myrddyn Phillips, resulting in the below:

LIDAR:  Ancient tumulus with trig pillar:  408.282m at SN 53485 39501

LIDAR:  Position in forestry:  408.510m at SN 53519 39583

LIDAR:  Summit in forestry:  408.700m at SN 53589 39599

During an on-site inspection data were gathered with the Trimble GeoXH 6000 from the highest ground on the ancient tumulus, resulting in:

Trimble:  Ancient tumulus with trig:  408.351m

The summit height produced by LIDAR analysis is 408.7m at SN 53589 39599 and its position in relation to that previously given comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies to any listed hill whose summit meets the following criteria; where there are a number of potential summit positions within close proximity and the highest point is not where previously given, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist, or when the summit of the hill is in a different field compared to where previously given, or when the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary that is judged to be a relatively recent man-made construct.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 Explorer map is being prioritised in favour of the 1:50,000 Landranger map for detailing these relocations.

Close up LIDAR summit image of Mynydd Llanybydder

LIDAR contouring implies that ground in the conifer plantation is higher than that at the ancient tumulus, therefore the relocated summit position is at SN 53589 39599 and this is approximately 150 metres north-east from where the previous listed 408m map heighted summit was given in the 1^st edition of the Y Pedwarau published by Europeaklist in May 2013 

 

The Trimble GeoXH 6000 positioned at the LIDAR summit of Mynydd Llanybydder

The full details for the hill are:

Group:  Mynydd Pencarreg

Name:  Mynydd Llanybydder

OS 1:50,000 map:  146

Summit Height:  408.7m (LIDAR)

Summit Grid Reference (New Position):  SN 53589 39599 (LIDAR)

Bwlch Height: c 287m (interpolation)

Bwlch Grid Reference:  SN 56098 40547 (interpolation) 

        

Drop:  c 122m (LIDAR summit and interpolated bwlch)

For details of the survey of this hill

Myrddyn Phillips and Aled Williams (December 2018)

Mapping Mountains – Trimble Surveys – Mynydd Pencarreg

31.07.18  Mynydd Llanybydder (SN 535 395)

Mynydd Llanybydder (SN 535 395)

I headed toward Mynydd Llanybydder after visiting Mynydd Pencarreg, these two hills are bisected by the upper reaches of the stream valleys of the Afon Duar and Afon Melinddwr, with the B4337 following the course of each between the small communities of Llansawel in the south-east and Llanybydder in the north-west.

Persistent rain fell as I drove up the minor road that covers the forested north-easterly slopes of this hill, thankfully the rain was not heavy and with a brisk breeze I hoped this would soon clear, although I wondered if I would have to wait an hour for it to do so, or venture out and get wet, miraculously when I arrived at the top of the road and parked adjacent to a cattle grid close to the access track that leads to one of three high transmitting masts that are positioned close to the summit of this hill, blue skies had appeared and the wet murk although still relatively close was being swept away.

Within a couple of minutes of setting off walking I had positioned the Trimble on the highest part of the ancient tumulus that also incorporates this hill’s triangulation pillar and stood back as five minutes of data were gathered and stored.

Gathering data at the old summit of Mynydd Llanybydder

During data gathering I looked out to the near forestry as I wanted to investigate where LIDAR gives the high point of this hill to be positioned, according to LIDAR this is not at the tumulus, and is immersed amongst the conifer plantation.

The Trimble set-up position at the old summit of Mynydd Llanybydder

Once five minutes of data were gathered I packed the Trimble away and headed toward the trees where a semblance of a track headed eastward, with the remains of felled ground to the south and forestry to the north. 

To follow this rough track I had one barbed wire fence to clamber over, as I did so, one prong of wire stabbed me and I emerged on the other side of the fence with blood spurting out of the wound.  I looked at my knee as blood freely flowed down my leg to my sock and boot, I’d grazed and scratched myself on wired fences a multitude of times over the years but spurting blood was somewhat of a novel experience.  I wiped the wound with a clump of grass to see where the cut was positioned, more blood quickly gushed out, deciding I was not going to die I pressed on in to the forestry.

Barb wired fences aren't my favoutite

I’d come prepared with a ten figure grid reference where LIDAR gives the high point of this hill to be situated and proceeded to use the Trimble as a hand-held device to get me to this point, thankfully this was not too far in to the trees.

It was hard to judge if this ground is higher than that beside the trig pillar on top of the ancient tumulus as there is no direct view between each due to the trees, and even if there was a direct view, it would still be difficult to judge which was higher purely by eye as the tumulus rises relatively steeply from the ground at its base whilst the ground heading in to the trees only rises gently over a much greater distance.

Looking back at the ancient tumulus and trig pillar from the periphery of the trees

Somewhere in the trees is the LIDAR summit of Mynydd Llanybydder

Once at the position LIDAR gives as the summit I visited a number of what could be construed as high points and exited the trees via a bit of branch bashing.  It felt good to be out of their darkened depths.

The Trimble marks the spot - the LIDAR summit of Mynydd Llanybydder

By now the blood from my knee wound had stopped spurting and on my way to the car I visited two engineers working at one of the masts, they kindly gave me wet wipes, plasters and a bandage, once the wound was cleaned I put three small plasters on it, thanked them for their help and walked the short distance back to my car, next stop the hills above Caerfyrddin (Carmarthen).

All cleaned up and ready to go

Survey Result:

Mynydd Llanybydder

Summit Height:  408.7m (LIDAR)

Summit Grid Reference:  SN 53589 39599 (LIDAR) (summit relocation confirmed)

Bwlch Height:  c 287m (interpolation)

Bwlch Grid Reference:  SN 56098 40547 (interpolation)

Drop:  c 122m (LIDAR summit and interpolated bwlch)

Dominance:  29.78% (LIDAR summit and interpolated bwlch)

For further details please consult the Trimble Survey Spreadsheet