Showing posts with label Pen yr Allt. Show all posts
Showing posts with label Pen yr Allt. Show all posts

Thursday, 21 August 2025

Mapping Mountains – Hill Reclassifications – The Welsh P15s

 

Pen yr Allt (SH 748 011) – Welsh Sub-P15 addition 

There has been an addition to the list of The Welsh P15s, 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 Pen yr Allt (SH 748 011)

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

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Pen yr Allt, and it is adjoined to the Banc Llechwedd Mawr group of hills, which are situated in the north-western part of South Wales (Region B, Sub-Region B1), and it is positioned with the A487 road to its west and the A489 road to its south, and has the town of Machynlleth towards the south.

When the listing that became known as The Welsh P15s was being compiled, this hill was not included in either the main list or the accompanying sub list, and was documented with an estimated c 13m of drop, based on an estimated c 74m summit height and an estimated c 61m 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 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 addition of this hill to Welsh Sub-P15 status is due to LIDAR analysis, resulting in a 73.8m summit height and a 59.7m bwlch height, with these values giving this hill 14.1m 0f drop, which is sufficient for it to be classified as a Welsh Sub-P15. 

 

The full details for the hill are: 

Group:  Banc Llechwedd Mawr 

Name:  Pen yr Allt 

OS 1:50,000 map:  135

Summit Height:  73.8m (LIDAR)                                                           

Summit Grid Reference:  SH 74846 01144 (LIDAR)                                                  

Bwlch Height:  59.7m (LIDAR) 

Bwlch Grid Reference:  SH 74986 01253 (LIDAR) 

Drop:  14.1m (LIDAR) 

 

Myrddyn Phillips (August 2025)

 

 

  

Tuesday, 14 September 2021

Mapping Mountains – Significant Name Changes – The Welsh P15s

 

Pen yr Allt (SH 429 917) 

There has been a Significant Name Change to a hill that is listed in The Welsh P15s, 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 Pen yr Allt (SO 429 917)

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

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10th May 2019. 

The Welsh P15s by Myrddyn Phillips

The hill is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the coast to its north, and is encircled by minor roads with the A5025 road farther to its north and the B5111 road farther to its east, and has the town of Amlwch towards the north-east. 

When the listing that became known as The Welsh P15s was being compiled, this hill was listed under the point (Pt. 69m) notation with 15m of drop, based on the 69m summit spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map and the 54m bwlch spot height that appears on the Ordnance Survey 1:25,000 Explorer map. 

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

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 191 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 Pen yr Allt in the apportionments, with the details on the Tithe map appearing in the parish of Amlwch and in the county named as Anglesey. 

Extract from the apportionments

Therefore, the name this hill is now listed by in The Welsh P15s is Pen yr Allt and this derived from the Tithe map. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Pen yr Allt

Previously Listed Name:  Pt. 69m 

OS 1:50,000 map:  114

Summit Height:  69.4m (LIDAR)                                                           

Summit Grid Reference:  SH 42925 91717 (LIDAR) 

Bwlch Height:  55.1m (LIDAR) 

Bwlch Grid Reference:  SH 43244 91030 (LIDAR) 

Drop:  14.3m (LIDAR) 

 

Myrddyn Phillips (September 2021)

 

 

 

 

 

Sunday, 12 September 2021

Mapping Mountains – Hill Reclassifications – The Welsh P15s


Pen yr Allt (SH 429 917) – Welsh P15 reclassified to Welsh Sub-P15 

There has been a reclassification to the list of The Welsh P15s, 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 Pen yr Allt (SH 429 917)

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

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Pen yr Allt and this was derived from the Tithe map and it is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the coast to its north, and is encircled by minor roads with the A5025 road farther to its north and the B5111 road farther to its east, and has the town of Amlwch towards the north-east. 

When the listing that became known as The Welsh P15s was being compiled, this hill was included in the main P15 list with 15m of drop, based on the 69m summit spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map and the 54m bwlch spot height that appears on the Ordnance Survey 1:25,000 Explorer map. 

Extract from 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 to Welsh Sub-P15 status is due to LIDAR analysis, resulting in a 69.4m summit height and a 55.1m bwlch height, with these values giving this hill 14.3m of drop, which is insufficient for it to be included in the main list of The Welsh P15s. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Pen yr Allt 

OS 1:50,000 map:  114

Summit Height:  69.4m (LIDAR)                                                           

Summit Grid Reference:  SH 42925 91717 (LIDAR) 

Bwlch Height:  55.1m (LIDAR) 

Bwlch Grid Reference:  SH 43244 91030 (LIDAR) 

Drop:  14.3m (LIDAR) 

 

Myrddyn Phillips (September 2021)

 

 

 

 

  

Saturday, 31 July 2021

Mapping Mountains – Hill Reclassifications – 200m Twmpau

 

Pen yr Allt (SH 842 025) – 200m Sub-Twmpau addition

There has been confirmation of an addition to the list of 200m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips. 

Pen yr Allt (SH 842 025)

The criteria for the list that this reclassification 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 200m Twmpau by Myrddyn Phillips

The name the hill is listed by is Pen yr Allt and it is adjoined to the Pumlumon group of hills which are situated in the north-western part of Mid and West Wales (Region B, Sub-Region B2), and it is encircled by minor roads with the A470 road farther to its north-east, and has the village of Comins-coch towards the north-east. 

When the original 200m height band of Welsh P30 hills was 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. 

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 25m of drop, based on the 267m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 242m bwlch height based on interpolation of 10m contouring between 240m – 250m. 

Extract from 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. 

LIDAR summit image of Pen yr Allt (SH 842 025)

Currently LIDAR only covers the summit area of this hill and as the summit and bwlch have now been surveyed with the Trimble GeoXH 6000 it is this result that is being prioritised for listing purposes. 

The Trimble GeoXH 6000 gathering data at the bwlch of Pen yr Allt

The Trimble GeoXH 6000 gathering data at the summit of Pen yr Allt

Therefore, the confirmation of the addition of this hill to 200m Sub-Twmpau status is due to LIDAR summit analysis and a subsequent Trimble GeoXH 6000 survey, resulting in a 266.6m summit height and a 241.9m bwlch height, with these values giving this hill 24.7m of drop, which is sufficient for it to be classified as a 200m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Pumlumon 

Name:  Pen yr Allt 

OS 1:50,000 map:  135, 136

Summit Height:  266.6m (converted to OSGM15) 

Summit Grid Reference:  SH 84232 02576 

Bwlch Height:  241.9m (converted to OSGM15) 

Bwlch Grid Reference:  SH 84202 02341 

Drop:  24.7m 

 

Myrddyn Phillips (July 2021)

 

 

 

Sunday, 23 May 2021

Mapping Mountains – Trimble Surveys – Pumlumon


30.03.21  Mynydd Tŷ’r Sais (SH 855 004), Briwnant (SH 847 017), Ffridd Pen y Graig (SH 842 018) and Pen yr Allt (SH 842 025) 

Ffridd Pen y Graig (SH 842 018)

The first true warmth of spring was savoured today, which for me is unusual as I am prone to suffer in the heat.  But winter can be oppressive with shortened day light hours and grey overbearing sky’s that during this year were only compounded by Covid restrictions, therefore the new growth and today’s warmth brought on by seasonal change highlighted a new beginning which conveniently matches many Covid restrictions recently being lifted. 

Today I wanted to visit four hills, with the first; Mynydd Tŷ’r Sais being a candidate for reclassification to P30 status.  These hills can be easily combined from the small community of Darowen and would for me, complete this block of land, as I had visited and surveyed adjacent hills to the west and also the east in recent years. 

I was parked and walking down a steep paved lane leading to Tan-llan by just past 8.30am.  I had a thin one skin jacket and gloves on as although the forecast of warn weather would quickly materialise the early morning still had a lingering chill. 

Chilled morning

Beyond Tan-llan the narrow paved lane deteriorated to a rough track, this fords a stream at its low point.  The adjacent fields were dew soaked with the sound of bleating lambs echoing through the morning mist.  The latter cloaked the hills but soon their tops emerged with just the last vestiges of mist clinging to their sides.  It was a beautiful morning to be out in this part of the world. 

Low mist still clung to the valley

I wanted to access Mynydd Tŷ’r Sais from the west; this involved the use of a private track.  Close to Rhos-Drynog farm I stood back as a number of sheep were being ushered from an adjacent field across the track to the opposing field.  The farmer who was on a quad bike pulled up and we chatted for a number of minutes.  He pointed out Maen Llwyd; an impressive standing stone that I had been close to lower on the track.  We conversed about the hills and he gave me names for a number of them.  He kindly let me continue up the track and I left after thanking him. 

Rheinallt Wigley

By now it was warming up and I had already dispensed with my thin gloves and soon afterward my jacket was packed away.  It would remain warm for the rest of the day, with later reports that Kew Gardens had recorded the warmest March day in Britain since 1968. 

The track leading to the first hill of the day

I followed the track ever upward to sheep pens and soon left it to strike up over grazing fields to a small conifer plantation, beyond which I followed the ridge fence heading up toward the top of the hill.  This hill is given a 359m spot height on contemporary Ordnance Survey 1:25,000 Explorer maps, but the summit analysis programme produced by Joe Nuttall and investigative work conducted by Ronnie Bowron indicated that its true summit is higher, and that in all likelihood its drop value exceeds 30m. 

The lower 359m spot heighted top is on the right and the higher 362.2m summit is on the left

I love surveying such hills and today the conditions were perfect with hardly a breath of breeze and with warmth this meant I could take my time and survey every point deemed necessary.  Surprisingly this consisted of only one on the summit area, with the highest point easily identified.  However its bwlch had a number of options for its critical point and I surveyed three in all, with each having undulations between.  This took just over an hour to complete, but will give confidence toward this hill’s drop value and therefore status. 

Gathering data at the summit of Mynydd Tŷ'r Sais with the lower 359m spot heighted top in the background

Leaving the bwlch I descended toward Lluest-cethingrych; an abandoned remnant when families and shepherds would use these hills from higher habitations.  The ruined house now looked down on a green track with its mature trees still shielding it from the worst of the weather.  Such places dot the upland landscape and all could tell a story of times long gone and forgotten. 

The old ruin of Lluest-cethingrych

The green track continued gravelled on the opposing banks of the Nant Tŷ’r Sais, this contoured around a hillside to the narrow paved lane east of Darowen.  On the way I stopped and smiled and took a few photos of an Argos container which shone bright sky blue in the morning’s sunshine.  It looked completely out of place amongst such beautiful and gentle countryside, but for me, it summed up one aspect why I love Wales so mush.  This country is not forensically presented where everything looks twee without a blade of grass out of place, it is lived in and all the better for such oddities. 

Looking completely out of place but still rather appealing

Ahead lay the connecting bwlch of Ffridd Pen y Graig, I’d investigated its surrounds via a Google car on my laptop and the point to survey looked as if it was submerged under a thin strip of trees that followed the valley bottom. 

Looking down on the bwlch of Ffridd Pen y Graig

I accessed the low field where the bwlch was placed via a gate and circumvented as much of the reed grass that grew near its flattest part as I could.  It was relatively easy to pinpoint the approximate position of the bwlch which was placed in a depression beside a fence and under a number of trees.  I imagined I’d be waiting for an age for the Trimble to attain the 0.1m accuracy level before data should be logged, but having set the equipment up I checked it after a couple of minutes and there was the magic number, I quickly pressed ‘Log’ and scampered away to sit on a mossed bow and waited for the allotted data to be gathered and stored. 

Gathering data at the bwlch of Ffridd Pen y Graig

After packing the Trimble away I clambered over the near fence and walked across a field before using another fence to get on to a track on the edge of forestry.  This gave me access to a steep field where the warmth battered me as I ever so slowly crept uphill, resting frequently, but height was gained and I eventually emerged beside a gate which gave access to the upper part of the hill. 

Mynydd Tŷ'r Sais (SH 855 004)

Gates and sheep paths led me up toward the summit of Briwnant; my second hill of the day.  I was glad to reach its high point.  The sky was blue and skylarks sang and the warmth gave an early summer feeling. 

Briwnant (SH 847 017)

I spent a number of minutes assessing the summit area of Briwnant and once I’d chosen the spot for Trimble placement the equipment was soon set up gathering data.  During data collection I sat and looked down on a herd of cows as they slowly wandered down the valley, conveniently away from where the next survey was going to take place. 

Gathering data at the summit of Briwnant

The next survey was at the connecting bwlch between Briwnant and Ffridd Pen y Graig and was positioned close to a fence.  I used one of the fence posts to give the Trimble a semblance of elevation and gathered the allotted data.  This process took an inordinate amount of time as I set the equipment up and closed it down on a number of occasions as the 0.1m accuracy level was not attained.  However, perseverance can be beneficial and having re-positioned it the magic number appeared and I sat below it as it quietly beeped away gathering its all-important data.  This at least gave me a well-earned rest and by the time I set off up the steepening field in front I felt almost brand new! 

Gathering data at the summit of Ffridd Pen y Graig

The summit of Ffridd Pen y Graig consists of three potential highest points.  I assessed these from a number of directions and having decided which I thought the highest set the Trimble up with its internal antenna aligned with the highest bit of mossed rock.  Before pressing ‘Log’ I stood and watched the whole upper part of the summit delicately move in motion with the breeze as it was covered in the most delightful spider webs and these ebbed in the breeze almost as if alive.  The little spiders also scampered across the yellowed outer shell of the Trimble as it gathered summit data. 

Gathering data at the bwlch of Pen yr Allt

I was nearing the end of the walk and just had one bwlch and summit to survey; this was for Pen yr Allt, a sub hill which connects to Ffridd Pen y Graig.  I spent a number of minutes assessing its connecting bwlch before choosing the spot for Trimble placement.  The summit of Pen yr Allt is covered by LIDAR, the only one to be so of the points I had surveyed during the day, because of this its position was easy to identify, but just to be on the safe side I took a second data set from a nearby small grassed hummock. 

The way back to Darowen

Once the Trimble had gathered its twelfth data set of the day I closed it down, packed it away and retraced by steps over the connecting bwlch to a public footpath and stiles as they strode out across late afternoon sun drenched fields toward the sleepy surrounds of Darowen.  It had been another good day on the hill.

 

Survey Result: 

 

Mynydd Tŷ’r Sais

Summit Height:  362.2m (converted to OSGM15) (significant height revision)

Summit Grid Reference:  SH 85514 00483 (summit relocation confirmed) 

Bwlch Height:  329.9m (converted to OSGM15)

Bwlch Grid Reference:  SH 86220 00690

Drop:  32.2m (Sub-Trichant reclassified to Trichant)

Dominance: 8.90%

 

 

Briwnant

Summit Height:  284.2m (converted to OSGM15)

Summit Grid Reference:  SH 84709 01728 

Bwlch Height:  248.7m (converted to OSGM15)

Bwlch Grid Reference:  SH 84556 01935

Drop:  35.5m

Dominance: 12.49%

 

 

Ffridd Pen y Graig

Summit Height:  296.8m (converted to OSGM15)

Summit Grid Reference:  SH 84242 01824 

Bwlch Height:  189.5m (converted to OSGM15)

Bwlch Grid Reference:  SH 85325 01537

Drop:  107.3m

Dominance: 36.15%

 

 

Pen yr Allt

Summit Height:  266.6m (converted to OSGM15)

Summit Grid Reference:  SH 84232 02576 

Bwlch Height:  241.9m (converted to OSGM15)

Bwlch Grid Reference:  SH 84202 02341

Drop:  24.7m (200m Sub-Twmpau addition)

Dominance: 9.26%

 

 

 

For further details please consult the Trimble Survey Spreadsheet