Mapping Mountains – Summit Relocations – 100m Twmpau

Parc Llwyn Du (SN 428 188)

There has been a Summit Relocation to a hill that is listed in the 100m Twmpau, with the summit height and its location, drop and status of the hill initially confirmed by LIDAR analysis and subsequently by a summit survey with the Trimble GeoXH 6000 which were conducted by Myrddyn Phillips, with latter taking place on the 31^st July 2018.

Parc Llwyn Du (SN 428 188)

The criteria for the list that this summit relocation applies to are:

100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

The name of the bounded land where the summit of this hill is situated is Parc Llwyn Du and this was derived from the Tithe map, and it is the name that this hill is now listed by.  The hill is adjoined to the Mynydd Sylen group of hills, which are situated in the western part of South Wales (Region C, Sub-Region C1), and is positioned with the A 48 road to its south and the B 4300 road to its north, and has the town of Caerfyrddin (Carmarthen) to the north-west.

If wanting to visit the hill permission to do so should be sought as the summit area is not a part of designated open access land, for those wishing to do so the nearest public footpath is to the south of the summit.

When the original Welsh 100m P30 list was published on Geoff Crowder’s v-g.me website the summit location of this hill was given to the 104m spot height adjoined to a triangulation pillar that appeared on contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps and positioned at SN 423 186.  However, this trig pillar is placed on a covered reservoir that is considered a recent man-made construct and therefore not a part of the natural summit of the hill.

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

The details for this hill were re-examined when the Ordnance Survey Interactive Coverage Map hosted on the Geograph website became available online and this map also gave a 104m spot height positioned at SN 428 188, and which is placed on natural ground.  However, it was not until LIDAR became available that an accurate height comparison could be made between these two positions.  

Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website

LIDAR image of Parc Llwyn Du

The summit height produced by DTM LIDAR analysis is 104.1m at SN 42895 18829, with the summit subsequently surveyed using the Trimble GeoXH 6000 resulting in a 104.3m summit height positioned at SN 42895 18827, and its position in relation to that originally 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.

The summit height produced by the Trimble GeoXH 6000 is 104.3m and is positioned at SN 42895 18827, this position is approximately 30 metres east from where the 104m spot height appears on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website, and over 560 metres east north-eastward from where the summit was originally listed at this hill’s triangulation pillar.

 

The full details for the hill are:

Group:  Mynydd Sylen

Name:  Parc Llwyn Du

OS 1:50,000 map:  159

Summit Height:  104.3m (converted to OSGM15, natural summit)

Summit Grid Reference (new position):  SN 42895 18827

Bwlch Height:  73.4m (LIDAR)

Bwlch Grid Reference:  SN 43247 18917 (LIDAR) 

Drop:  30.8m (Trimble summit and LIDAR bwlch)

The Trimble set-up position at the summit of Parc Llwyn Du

For details on the summit survey of Parc Llwyn Du

Myrddyn Phillips (January 2019)

Mapping Mountains – Significant Name Changes – 100m Twmpau

Parc Llwyn Du (SN 428 188)

There has been a Significant Name Change to a hill that is listed in the 100m Twmpau, with the summit height and its location, drop and status of the hill initially confirmed by LIDAR analysis and subsequently by a summit survey with the Trimble GeoXH 6000 which were conducted by Myrddyn Phillips, with latter taking place on the 31^st July 2018.

Parc Llwyn Du (SN 428 188)

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

100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

The hill is adjoined to the Mynydd Sylen group of hills, which are situated in the western part of South Wales (Region C, Sub-Region C1), and is positioned with the A 48 road to its south and the B 4300 road to its north, and has the town of Caerfyrddin (Carmarthen) to the north-west.

The hill originally appeared in the 100m P30 list on Geoff Crowder’s v-g.me website under the invented name of Bryn Pen-sarn, with an accompanying note stating; Name from town to the North-West.

 

Bryn Pen-sarn

104m

SN423187

159

177

Name from town to the North-West

During my early hill listing I thought it appropriate to either invent a name for a hill, or use a name that appeared near to the summit of the hill on Ordnance Survey maps of the day.  My preference was to use farm names and put Pen, Bryn or Moel in front of them or as in this instance use the name given to a village and precede it with the word Bryn.  This is not a practice that I now advocate as with time and inclination place-name data can be improved either by asking local people or by examining historic documents, through this form of research an appropriate name for the hill can usually be found.

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 179 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 as Park Llwyndu in the apportionments, with the details on the Tithe map appearing in the parish of Llangunnor and in the county named as Carmarthen.

Extract from the apportionments

Therefore, the name this hill is now listed by in the 100m Twmpau is Parc Llwyn Du, and this was derived from the Tithe map.

The full details for the hill are:

Group:  Mynydd Sylen

Name:  Parc Llwyn Du

Previously Listed Name:  Bryn Pen-sarn

  

OS 1:50,000 map:  159

Summit Height:  104.3m (converted to OSGM15, natural summit)

Summit Grid Reference:  SN 42895 18827

Bwlch Height:  73.4m (LIDAR)

Bwlch Grid Reference:  SN 43247 18917 (LIDAR) 

Drop:  30.8m (Trimble summit and LIDAR bwlch)

For details on the summit survey of Parc Llwyn Du

Myrddyn Phillips (December 2018)

Mapping Mountains – Trimble Surveys – Mynydd Sylen

31.07.18  Parc Llwyn Du (SN 428 188)

Parc Llwyn Du (SN 428 188)

Having driven south and visited Mynydd Pencarreg (SN 575 432) and Mynydd Llanybydder (SN 535 395) I now had an afternoon in the sunshine to enjoy a number of hills just to the south of the Afon Tywi above Carmarthen, before a late afternoon meeting with a friend who was house sitting for the week in the town.

The first hill I wanted to visit is positioned above a meeting of minor roads to the south of the B4300, and it here where the bwlch of the hill is situated and also where I parked my car adjacent to an earthen track that has public right of way, this would give me access to the hill’s summit.

The bwlch of Parc Llwyn Du

LIDAR image of the bwlch of Parc Llwyn Du

The field where the summit of this hill is situated is named Parc Llwyn Du on the Tithe map and this is the name that the hill is now listed by in the Welsh P30 list.  I’d come prepared with ten figure grid references for both summit and bwlch provided by LIDAR analysis, but only had intention to survey the summit of the hill. 

LIDAR analysis gives the highest point of this hill beside a trig pillar at SN 42343 18691, which the Tithe map names as Llain Bolahaul, but as this is positioned on ground associated with a small covered reservoir I considered this point man-made and therefore concentrated on the eastern part of the hill where a natural summit exists that LIDAR gives as only 0.2m lower.

LIDAR image of the summit of Llain Bolahaul on the left and Parc Llwyn Du on the right

The track led toward a mast and another minor road, I only stayed on it for a short distance and soon gained height up the field to my north.  A gate then gave access toward its high point, with the field where this is situated contentedly being grazed by a large herd of cows.  As I walked up beside the staked perimeter the cows inquisitively headed my way, not a good sign for a surveyor!

A sign of things to come

I decided to try and bi-pass the cows and approach the summit from their rear, and clambered over two wired fences which thankfully led through gaps in adjacent hedges, one accessed the field to the immediate north, and the other gave me access back in to the field where the summit and the cows were positioned.  As soon as I emerged back in to the high field the cows were on me, slowly wandering my way, within a minute or two of finding the summit position I stood with about 30-40 cows surrounding me and the Trimble with an amorous bull no more than a few feet away who was enjoying mounting one of the herd, I thought any semblance of gathering Trimble data next to impossible as by now a number of cows were licking the equipment.

Friendly surveying assistants

I then spent a number of minutes gently encouraging the cows to back away from the Trimble, miraculously this worked and once it was gathering data I stood with my arms out stretched slowly encouraging them to take backward steps away from the equipment, and once five minutes of data were gathered and stored I ran toward the equipment and switched it off, by the time I had done this the cows were back edging their way toward the Trimble.

Gathering data at the summit of Parc Llwyn Du

I packed the Trimble away and stood looking at the cows for a while, after rubbing the noses of one or two I departed as they all followed me down the field.  It was only a short walk back on the track to where my car was parked; next stop was the summit of Lan (SN 441 196).

Survey Result:

Parc Llwyn Du (significant name change)

Summit Height:  104.3m (converted to OSGM15)

Summit Grid Reference:  SN 42895 18827 (summit relocation confirmed)

Bwlch Height:  73.4m (LIDAR)

Bwlch Grid Reference:  SN 43247 18917 (LIDAR)

Drop:  30.8m (Trimble summit and LIDAR bwlch) (100m Twmpau status confirmed)

Dominance:  29.58%

For further details please consult the Trimble Survey Spreadsheet