Mapping Mountains – Significant Height Revisions – 200m Twmpau

Clip y Gylfinhir (SH 223 284)

There has been a Significant Height Revision to a hill that is listed in the 200m Twmpau, with the hill’s height, drop and status confirmed by a survey with the Trimble GeoXH 6000 which was conducted by Myrddyn Phillips on the 28^th December 2014 and 3^rd October 2018 in good, clear conditions with hardly a breath of breeze.

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

200m Twmpau – Welsh hills at or above 200m and below 300m in height that have 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m 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 hill is Clip y Gylfinhir, and it is adjoined to the Pen Llŷn range of hills, which are situated in the western part of North Wales (Region A, Sub-Region A1), and it is positioned toward the western end of Pen Llŷn, and is encircled by a series of minor roads and has the small community of Y Rhiw towards the south.

Clip y Gylfinhir (SH 223 284)

As the summit of the hill is a part of designated open access land it can be approached from most directions, with public footpaths leading in to the access land from a variety of directions, and for those wishing a quick ascent of the hill there is parking space at the immediate base of the hill to its north-east.

When the original Welsh 200m P30 list was published on Geoff Crowder’s v-g.me website, this hill was listed in the accompanying Hills to be surveyed sub list with a 270m summit height which appears as a spot height on the Ordnance Survey 1:25,000 Explorer map.

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

The summit height produced by The Trimble GeoXH 6000 survey is 267.8m (converted to OSGM15), this is not a substantial height revision when compared to some revised heights, but it does come 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.  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 revisions.

The Trimble GeoXH 6000 gathering data at the summit of Clip y Gylfinhir

Therefore, this hill’s new summit height is 267.8m (converted to OSGM15) and this was produced by surveying with the Trimble GeoXH 6000, this is 2.3m lower than its previously listed height of 270m which appears as a spot height on the Ordnance Survey 1:25,000 Explorer map, however this new height is in accordance with the 5m contouring on OS Maps.

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Pen Llŷn

Name:  Clip y Gylfinhir

OS 1:50,000 map:  123

Summit Height (New height):  267.8m (converted to OSGM15)

Summit Grid Reference:  SH 22395 28472

  

Bwlch Height:  240.1m (converted to OSGM15)

Bwlch Grid Reference:  SH 22514 28524

Drop:  27.7m (converted to OSGM15)

For details on the 1^st survey of this hill

For details on the 2nd survey that significantly revised the summit height of this hill

Myrddyn Phillips (December 2018)

Mapping Mountains – Trimble Surveys – Yr Eifl

03.10.18  Clip y Gylfinhir (SH 223 284)  

Clip y Gylfinhir (SH 223 284)

Clip y Gylfinhir was previously surveyed with the Trimble GeoXH 6000 on the 28^th December 2014, the resulting height proved substantially lower than the 270m spot height that appears on the Ordnance Survey 1:25,000 Explorer map, and as the Standard Deviation and Estimated Accuracies indicated the data set was not good, I wanted to re-visit and survey this hill’s summit ever since.  The opportunity to do so was now here as Aled and I had visited Mynydd Penarfynydd and Mynydd y Graig and it was only a short drive from these hills to the parking area at the base of Clip y Gylfinhir, and whilst surveying this hill Aled could visit the adjacent Mynydd y Rhiw, a hill he had not previously been up.

Clip y Gylfinhir thrusts upward and is coned in profile, it stands out even from afar as a pimple like addition to the southern slopes of its higher neighbour; Mynydd y Rhiw, and the hill has association with the Tylwyth Teg; the mythological fairy like creatures of Welsh folklore.

As Aled headed north toward the trig pillar atop Mynydd y Rhiw I left a friendly Shetland pony beside my car and as it nuzzled its head against the boot, and hoped that it would not attempt to eat my rear wiper blade whilst I was on the hill!

Aled on the summit of Mynydd y Rhiw

A paved road leads to the adjacent mast and radar station that now sits beside Clip y Gylfinhir, from this paved road the hill thrusts upward, with it being steep on all sides.  I followed the road to its end and slowly plodded up the steep rocky slopes toward its summit where an autumnal breeze met me as it blew in from the sea.

The previous time this hill was Trimbled I’d placed the equipment aligned with the highest rock, this time I wanted the Trimble to be elevated above its immediate surrounds and therefore placed it on top of my rucksack which acted as an improvised tripod, having measured the offset between its internal antenna and the ground below I pressed ‘Log’ and waited for ten minutes of data to be gathered and stored.

Gathering data at the summit of Clip y Gylfinhir

The Trimble set-up position at the summit of Clip y Gylfinhir

As the Trimble gathered data I sat below it watching Aled making good progress up the path to the summit of Mynydd y Rhiw, he was descending the hill as the Trimble continued beeping away gathering its 600 individual datum points, once data were stored I closed the equipment down, packed it away and headed down to the paved road and arrived back at the car no more than a minute or so before Aled did likewise.

Survey Result:

Clip y Gylfinhir

Summit Height:  267.8m (converted to OSGM15) (significant height revision)

Summit Grid Reference:  SH 22395 28472

Bwlch Height:  240.1m (converted to OSGM15) (from previous Trimble GeoXH 6000 survey)

Bwlch Grid Reference:  SH 22514 28524 (from previous Trimble GeoXH 6000 survey)

Drop:  27.7m

Dominance:  10.34%

For details on the first Trimble survey of Clip y Gylfinhir

For further details please consult the Trimble Survey Spreadsheet

Mapping Mountains – Significant Height Revisions – Y Pellennig – The Remotest Hills of Wales

Whiteford Burrows (SS 448 964)

There has been a Significant Height Revision to a hill that now appears in the Y Pellennig – The Remotest Hills of Wales list due to LIDAR analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips.

LIDAR image of Whiteford Burrows

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

Y Pellennig – The Remotest Hills of Wales - Welsh hills whose summit is at least 2.5km from the nearest paved public road and the hill has a minimum 15m of drop, the list is a joint compilation between Myrddyn Phillips and Aled Williams and is available as a downloadable e-booklet or print-booklet version on Mapping Mountains Publications with the up-to-date master list available on the Mapping Mountains site in Google Doc format.

The name of the hill is Whiteford Burrows and it is adjoined to the Gŵyr group of hills, which are situated in the western part of South Wales (Region C, Sub-Region C1), and it is positioned overlooking Whiteford Point and the coast, and has the small community of Llanmadog towards the south.

As the hill is a part of designated open access land it can be approached from any direction, for those wishing to visit the Wales Coast Path approaches the hill from the south and follows land close to the coast and heads toward Whiteford Point, and the summit of the hill is only a short distance from this long distance path.

Prior to LIDAR analysis this hill was not catalogued as the uppermost contour given it on the Ordnance Survey 1:25,000 Explorer map is 5m, whilst the Ordnance Survey 1:50,000 Landranger map has no contours.  LIDAR gives a summit height of 28.3m, and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

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

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.  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 revisions.

Therefore, this hill’s new summit height is 29.6m and this was produced by LIDAR analysis, this is 24.6m higher than the uppermost 5m contour on the Ordnance Survey 1:25,000 Explorer map, however this new height is in accordance with the 5m contouring on OS Maps. 

 

LIDAR summit image of Whiteford Burrows

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Gŵyr

Name:  Whiteford Burrows

OS 1:50,000 map:  159

Summit Height (New height):  29.6m (LIDAR)

Summit Grid Reference:  SS 44870 96422 (hand-held GPS)

Bwlch Height:  9.2m (LIDAR)

Bwlch Grid Reference:  SS 44631 95701 (LIDAR) 

  

Drop:  20.4m (LIDAR)

Remoteness:  2.925km

Myrddyn Phillips and Aled Williams (December 2018)

Mapping Mountains – Trimble Surveys – Yr Eifl

03.10.18  Mynydd Penarfynydd (SH 220 265) and Mynydd y Graig (SH 227 274)  

Mynydd y Graig (SH 227 274)

The south-western Llŷn portrays a land that is apart, an end.  This is more so than a land that meets sea; as it portrays a differing life, one seldom encountered further inland.  This aspect is enhanced by narrow lanes, few signposts, dotted farms joined by earthen tracks, and tranquillity all of its own.  There are few other places in Wales that can compare.

Although I’d been on this part of the Llŷn many times before, it still held hills that I had not visited and today Aled and I wanted to investigate ones that we had both neglected until now.  Having visited Mynydd Ystum (SH 187 284) we headed east and parked on a narrow lane at the base of Mynydd y Graig, whose summit rose in castellated rock outcrops above.

To our south-west the Llŷn stretched seaward where Maen Gwenonwy, Ynys Gwylan Fawr, Ynys Gwylan Fach and Ynys Enlli were bathed in morning sunshine, all looking resplendent with only Maen Gwenonwy attached to the mainland by a slither of tidal debris.

Like bejeweled rocks cast in to the sea; (L-R) Ynys Gwylan Fach, Ynys Gwylan Fawr, Ynys Enlli and Maen Gwenonwy

The narrow track we were on led toward the connecting bwlch between Mynydd Penarfynydd and Mynydd y Graig, as it had been LIDARed we bi-passed it and joined the footpath leading to the summit of Mynydd Penarfynydd.

Mynydd Penarfynydd (SH 220 265)

The path led up at a gentle gradient to the triangulation pillar on the summit and a few minutes later the Trimble was set up and gathering data at the high point of the hill, during this Aled headed further down the ridge to sit and admire the view, I soon followed.

Gathering data at the summit of Mynydd Penarfynydd

Mynydd Penarfynydd is a part of a butting promontory where land meets the sea and although only relatively small in height it none the less gives a marvellous sense of height as it clings on above the sea, and today when bathed in early October sun it was a wonderful place to be.

Once the Trimble had gathered and stored its allotted data we retraced our route back down toward the connecting bwlch as greying cloud massed inland over the higher peaks of Eryri.

Ahead lay Mynydd y Graig, a fine and apt name for the hill.  We followed the main path around the hills eastern slopes instead of its narrow ridge path from the bwlch, this meant a steep ascent toward the ridge but gave endless seascapes on the way.

The summit of Mynydd y Graig is crowned by a number of large rocks, with two vying for the accolade of highest point, both were Trimbled.  Aled arrived at the summit first, I soon joined him and then delicately positioned the Trimble on the high point of the first large rock, aligning its internal antenna to its highest point and for ease of placement this meant the equipment was pointing west, resulting in it logging on to only one or two satellites, therefore I repositioned it pointing north-eastward with the end of the equipment only a centimetre or so from Trimble oblivion.  Before activating the Trimble to gather data I wedged it in place with three small rocks, then pressed ‘Log’ and hoped it would still be in situ once the allotted data were gathered and stored.

Aled at the summit of Mynydd y Graig

During this first summit survey Aled visited the second large rock and looked back toward the first where the Trimble was positioned, he thought both close in height and therefore the second large boulder definitely needed Trimbling.

The second boulder proved a little easier to position the Trimble on top of, and again I used the same three small rocks to wedge it in place during data collection.  As Aled waited near the first large boulder I sat and savoured the view, and thought that these two hills when combined give a marvellous small walk.

Gathering data at the second large boulder with Aled standing at the top of the first large boulder and what proved to be the summit of Mynydd y Graig

Once the Trimble was packed away I re-joined Aled and we headed down following a narrowing footpath back to the small lane where the car had been left, next stop was a short distance to our north with a visit to Clip y Gylfinhir for me and Mynydd y Rhiw for Aled.

Survey Result:

Mynydd Penarfynydd

Summit Height:  177.4m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 22008 26580 (Trimble GeoXH 6000

Bwlch Height:  142.0m (LIDAR)

Bwlch Grid Reference:  SH 22322 26725 (LIDAR)

Drop:  35.4m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  19.93% (Trimble GeoXH 6000 summit and LIDAR bwlch)

Mynydd y Graig

Summit Height:  242.5m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 22785 27433 (Trimble GeoXH 6000)

Bwlch Height:  186.0m (LIDAR)

Bwlch Grid Reference:  SH 22762 27947 (LIDAR)

Drop:  56.5m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  23.31% (Trimble GeoXH 6000 summit and LIDAR bwlch)

For further details please consult the Trimble Survey Spreadsheet

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)