Mapping Mountains – Summit Relocations – Y Trichant – The 300m Hills of Wales

 

Mynydd Du (SH 805 084) 

There has been a Summit Relocation to a hill that is listed in the Y Trichant – The 300m Hills of Wales, with the summit height, bwlch height and their location, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Mynydd Du (SH 805 084)

The criteria for the list that this summit relocation 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 Mynydd Du, and it is adjoined to the Aran Fawddwy group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and it is positioned with minor roads to its north and south, the A487 road to its west and the A470 road to its east, and has the village of Aberllefenni towards the west north-west. 

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

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 19m of drop, based on the 335m summit spot height positioned at SH 80470 08382 that appears on the Ordnance Survey 1:50,000 Landranger map and the 316m 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. 

Extract from the Ordnance Survey 1:50,000 Landranger 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 Mynydd Du (SH 805 084)

The summit that LIDAR identifies is 335.8m in height and positioned at SH 80572 08424, with the caveat that there is only partial LIDAR coverage for the summit area of this hill, and this comes within the parameters of the Summit Relocations used within this page heading, these parameters are: 

The term Summit Relocations applies to when the high point is positioned in a different field, to a different feature such as a conifer plantation, within a different map contour, a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is considered a relatively recent man-made construct, 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. 

Therefore, the listed summit height of this hill is 335.8m and its new position is SH 80572 08424, this position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and is approximately 100 metres north-eastward from where the previously listed summit is positioned. 

 

The full details for the hill are:

Group:  Aran Fawddwy 

Name:  Mynydd Du 

OS 1:50,000 map:  124, 125

Summit Height:  335.8m (LIDAR)                                                           

Summit Grid Reference (New Position):  SH 80572 08424 (LIDAR) 

Bwlch Height:  314.9m (LIDAR) 

Bwlch Grid Reference:  SH 80738 08624 (LIDAR) 

Drop:  20.9m (LIDAR) 

 

Myrddyn Phillips (February 2022)

 

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

Mynydd Du (SH 805 084) – Sub-Trichant addition

There has been an addition 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 Mynydd Du (SH 805 084)

The criteria for the list that this addition 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 Mynydd Du, and it is adjoined to the Aran Fawddwy group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and it is positioned with minor roads to its north and south, the A487 road to its west and the A470 road to its east, and has the village of Aberllefenni towards the west north-west. 

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

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 19m of drop, based on the 335m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger map and the 316m 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. 

Extract from the Ordnance Survey 1:50,000 Landranger 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 addition of this hill to Sub-Trichant status is due to LIDAR analysis, resulting in a 335.8m summit height and a 314.9m bwlch height, with these values giving this hill 20.9m of drop, which is sufficient for it to be classified as a Trichant. 

 

The full details for the hill are: 

Group:  Aran Fawddwy 

Name:  Mynydd Du 

OS 1:50,000 map:  124, 125

Summit Height:  335.8m (LIDAR)                                                           

Summit Grid Reference:  SH 80572 08424 (LIDAR) 

Bwlch Height:  314.9m (LIDAR) 

Bwlch Grid Reference:  SH 80738 08624 (LIDAR) 

Drop:  20.9m (LIDAR) 

 

Myrddyn Phillips (February 2022)

 

  

Mapping Mountains – Trimble Surveys – Moel y Gamelin

18.12.19  Mynydd Du (SJ 214 571)  

Driving north toward Wrexham I wondered what I was doing, as clagged grey hung deeply across the countryside with chilled frost adding beauty to an otherwise enclosed scene.  I was hoping to visit four P30s over three walks, ending close to Mold where a short drive in my car would take me to Mark’s house for our onward journey to Beddgelert to meet Aled for an early evening pre-Christmas meal.

There was a beautiful crisp blue sky and vivid colour yesterday, and yet today was diametrically opposite.  However, as I turned north-westward toward the base of my first hill of the day the clag was not as thick as that around Welshpool, which made navigation easier, although wandering to the top of a relatively high field is never the most difficult.

Having parked to the south of the hill beside a church I followed a public footpath up in to the gloom.  It was good to be out, slowly immersing myself in ethereal mist and chilled air with frost edged patches clinging to the dulled green of winter.

The path led past a pool enclosed by stunted trees, I stopped and looked out on to a quiet scene.  Just a breath of breeze stirred the trees; this increased in strength as I gained height to open land, but only blew stronger later in the day on my last hill.

A misted and chilled scene

The path led me to the upper field where murky silhouettes of grazing cattle would ebb in and out of view.  The high point was close to where I crested the upper broad ridge and near to the remains of a collapsed stone wall.

The summit point was easy to identify and within a few minutes I had placed the Trimble atop my rucksack, measured the offset between its internal antenna and the ground below, and once the 0.1m accuracy level was attained before data should be logged, activated it to gather data.

Gathering data at the summit of Mynydd Du

By this time the one or two murky silhouettes of distant cattle had turned in to a small herd who sometimes stood and watched and other times frisked their way this way and that, a seemingly playful bunch.

Once data were gathered and stored, I closed the equipment down, packed it away and left the summit reversing my inward route back past the pool and down to my car.  A fine start to the morning’s bagging. 

Survey Result:

Mynydd Du 

Summit Height:  379.5m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SJ 21470 57139 (Trimble GeoXH 6000)

Bwlch Height:  c 342m (interpolation)

Bwlch Grid Reference:  SJ 21266 57457 (interpolation)

Drop:  c 37m (Trimble GeoXH 6000 summit and interpolated bwlch)

Dominance:  9.87% (Trimble GeoXH 6000 summit and interpolated bwlch)

For further details please consult the Trimble Survey Spreadsheet