Mapping Mountains – Significant Height Revisions – 200m Twmpau and Y Trechol - The Dominant Hills of Wales

Pen y Berth (SJ 081 127)  

There has been a Significant Height Revision to a hill that is listed in the 200m Twmpau (thirty welsh metre prominences and upward) as well as Y Trechol - The Dominant Hills of Wales, and which was initiated by a survey with the Trimble GeoXH 6000, with these details being retrospective as the survey that resulted in this height revision was conducted on 19^th October 2014.

The criteria for the two listings that this height revision affects are:


200m Twmpau - these are the Welsh hills at or above 200m and below 300m in height that have a minimum drop of 30m. 

Y Trechol - The Dominant Hills of Wales - these are the Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those addition Welsh P30 hills whose prominence is 33% or more and below 50% of their absolute height.

The name of the hill is Pen y Berth and it is situated in the Y Berwyn range of hills and the survey with the Trimble GeoXH 6000 was conducted in the company of Mark Trengove on a colourful autumnal day in October.

The hill can be accessed from 1km east of the small community of Dolanog on a track that heads north-west and then east to sneak up to the summit from the opposing side of the hill.  The summit area of the hill is given two 280m uppermost ring contours aligned east and west of one another on Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps, with each contour ring given a 282m spot height on the Ordnance Survey enlarged mapping hosted on the Geograph website.

The following results are those obtained with the Trimble GeoXH 6000 for the two points surveyed:

Eastern 282m spot height:  283.7m (converted to OSGM15) at SJ 08322 12748

Western 282m spot height at SJ 08012 12780 not surveyed

Easterly high point of western 280m ring contour:  287.5m (converted to OSGM15) at SJ 08126 12730

The land at SJ 08126 12730 was visually judged to be higher than the land at SJ 08012 12780, therefore the latter position was not surveyed.  The height given this hill on the Ordnance Survey enlarged mapping hosted on the Geograh website is 282m, with the height resulting from the survey with the Trimble GeoXH 6000 being 287.5m (converted to OSGM15).

Therefore this hill’s new summit height is 5.5m higher than its previously listed height which came from the 282m spot height on the Ordnance Survey enlarged mapping hosted on the Geograph website.

The full details for the hill are:

Cardinal Hill:  Carreg y Big

Summit Height (New Height):  287.5m (converted to OSGM15)

Name:  Pen y Berth

OS 1:50,000 map:  125

Summit Grid Reference:  SJ 08126 12730 

 

Drop:  134.2m (converted to OSGM15)

Dominance:  46.68%

Pen y Berth (SJ 081 127) a hill whose height has been significantly revised

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

Myrddyn Phillips (August 2015)

Mapping Mountains – Summit Relocations – 200m Twmpau and Y Trechol - The Dominant Hills of Wales

Pen y Berth (SJ 081 127)  

There has been a Summit Relocation to the 200m Twmpau (thirty welsh metre prominences and upward) list and also the Y Trichant - The Dominant Hills of Wales list due to a survey with the Trimble GeoXH 6000, and these details are retrospective as the survey that resulted in this summit relocation was conducted on 19^th October 2014.

The survey was conducted in the hills just to the east of the small community of Dolanog, with the hill positioned above the B4382 which is to its south, and above the Afon Efyrnwy which is to its north.

The hill was surveyed in the company of Mark Trengove on a day when the westerly showers were being pushed east; thankfully all missed us as we visited two hills over two separate walks.

The hill is named Pen y Berth, and its prioritised summit position was listed at SJ 080 127 as this is where its 282m summit spot height appears on the Ordnance Survey enlarged mapping hosted on the Geograph website.  This map also shows a twin 282m map heighted summit at SJ 083 127.

The position of the spot height at SJ 080 127 is immersed in a conifer plantation, whilst the position of the spot height at SJ 083 127 is on open ground with small deciduous trees growing near to it.  The latter position was surveyed with the Trimble GeoXH 6000 as was a position on the periphery of the conifer plantation that was visually higher than the remaining ground within the forestry.

The result of each survey appears below:

282m spot height at SJ 083 127 came to 283.7m (converted to OSGM15) at SJ 08322 12748

new summit position came to 287.5m (converted to OSGM15) at SJ 08126 12730

282m spot height at SJ 080 127 was not surveyed as its position was deemed lower compared to the new summit position

The position of the relocated summit is at SJ 08126 12730 and is the top of featureless ground under Larch trees, this is not given a spot height on current Ordnance Survey maps but the Trimble result gave it as 5.5m higher and approximately 80 metres eastward from where the westerly 282m map spot height is positioned on the ground.

The full details for the hill are:

Cardinal Hill:  Carreg y Big

Summit Height:  287.5m (converted to OSGM15)

Name:  Pen y Berth

OS 1:50,000 map:  125

Summit Grid Reference (New Position):  SJ 08126 12730 

 

Drop:  134.2m (converted to OSGM15)

Dominance:  46.68%

The Trimble GeoXH 6000 set up at the new summit position of Pen y Berth, with the old position of the prioritised summit approximately 80 metres behind the Trimble and further into the conifer plantation

For details on the survey that relocated the summit of this hill please click {here}

Myrddyn Phillips (October 2014)

Mapping Mountains – Trimble Surveys – Y Berwyn

13.12.14  Ffridd (SJ 084 141), Allt Dolanog (SJ 067 134) and Pen y Berth (SJ 081 127, only bwlch surveyed)   

Allt Dolanog (SJ 067 134)

As I walked up the track from Dolanog the early morning chill mist rose with a silver sheen accentuating the overnight frost.  Overhead was blue sky and with a forecast of dry sunny conditions the day was set fair.

The silver sheen of winter

There were two hills I wanted to visit today and when combined the map indicated a good small circuit.  Dolanog consists of a few houses and is placed in the heart of northern mid-Wales with the Afon Efyrnwy (River Vyrnwy) running wild on the hamlet’s southern outskirts.

The track leading out of Dolanog skirted the south-eastern slopes of Allt Dolanog, which was to be my second and last hill of the day.  Although the overnight chill had left clear skies and morning frost, the accumulated rain over several days meant that the track was puddle ridden in places.  I’d come well prepared wearing winter wellies instead of walking boots.

There is a beauty in winter walking, a sense that the world is in hibernation with warmth emanating from hillsides of sunshine and yet because of the sun’s low angle much of the countryside can remain in its chill refinement, this was echoed in a delicate formation of frost crystals on leaves and bracken and yet within a matter of a few metres I walked into sunshine and the bright late year ebb of life in ragwort that was still clinging to its slender thread of life.

Frost on leaf

Sunshine on ragwort

The first hill I wanted to visit is named Ffridd on the Tithe map, having been first listed under the name of Penygorddyn which appears near to its summit but which is applicable to an ancient settlement lower on the hill and now covered in conifer plantation.  As the track contoured around the eastern slopes of Allt Dolanog it continued toward the first hill which is given the height of 296m on the Ordnance Survey map.  This hill lay ahead with its summit covered in sunshine and warmth whilst the track was still frost covered.

The track leading up to Ffridd, which is in the centre background

Soon the track diverged and I headed on its upward path into the conifer plantation, the going was relatively easy except for one part where fallen trees and overgrown undergrowth slowed progress, but once over and through the obstacle the track crept upward into the sunshine and the edge of the trees, beyond was the welcome site of open hillside.

First glimpse of open hillside through the conifers

Once over a fence I walked up to the high point and was confronted by a number of sheep, all in unison confidently marching toward me, once they realised I wasn’t the local farmer and had no feed for them they politely kept their distance.  The high point of the hill is crowned by rock and as I set the Trimble up to gather its customary five minutes of data I stood back and admired the high Aran which were covered in snow and cast a winter outlook out to the west, especially so when framed against the manicured green fields to their east.

Perched on the high point of Ffridd

It's always fun trying to balance and align the Trimble with the highest point of a rocky summit

The data produced by the Trimble will be interesting for this hill as I’d previously given it an estimated 32m of drop based on its 296m summit height and an estimated bwlch height of 264m.  This had been revised in recent years when the Ordnance Survey enlarged mapping on the Geograph website became available as this mapping has a 268m spot height on the area of the bwlch, giving the hill only 28m of drop.

After packing the Trimble away I set off northward toward the bwlch over and around intermittent bumps and then down a narrow lane.  The critical bwlch lay just off the lane in a closely cropped grassy field where its valley to valley traverse spread out in a seemingly never ending lushness of flatness.  I took two data sets and hoped that the hill would attain a minimum of 30m of drop as it would be a fine addition to the Twmpau.

Gathering data at the bwlch area of Ffridd

My planned route crossed a stream named Nant Dolwar that was no more than a slender blue slither on the map, as the fields led down steeply to the stream I was glad I was wearing wellies as it was in spate and bubbling downward.  Too wide to jump and even at its shallowest crossing it was too deep to wade without getting wet, thankfully my walking boots had been left at home and even at the crossing place I chose the water almost came over the top of my wellies.  I stood in the middle of the steam and took a few photos and watched as light caught mist and played upon its delicateness, a microcosm of wonder easily missed and one that would only remain for an indefinite period.

The Nant Dolwar

Glad I wore my wellies

Once over the stream I walked up a field to a gate and out onto another narrow lane which led upto a steep ice encrusted road.  The road led to the connecting bwlch for Allt Dolanog and the next survey of the day which was in a field near to a cold looking large puddle.

Gathering data at the critical bwlch of Allt Dolanog

After gathering data at the bwlch I walked up the last few metres of road toward a gate which gave access to open hillside leading upto the summit of Allt Dolanog.  As I approached the gate three dogs scampered down the path on the opposite side and following was a smiling face belonging to Karen McMahon.  We stopped and chatted, Karen was out Nordic walking with her dogs in tow, all were enjoying the openness of countryside.

Karen moved to a small holding in this area a number of years ago and is a fully qualified Pilates and Nordic Walking instructor.  I smiled at the thought of Nordic Walking being practiced in mid-Wales and smiled again when Karen told me her surname was McMahon and that she came from Chorley in Manchester.  I joked that the walking style for mid-Wales and the surname for Lancashire both seemed out of place.  Karen runs classes in Nordic Walking and can be contacted at www.fitffarm.co.uk  have a look at her website as the walking style and Karen’s philosophy is based on fitness and good nutrition.

Great day for a Nordic Walk, Karen McMahon out with her three dogs

As we said our goodbye’s Karen headed down the lane toward Dolanog and I continued upward on a good green track toward the summit of Allt Dolanog.  This hill is covered in patches of bracken all now bronzed from the onset of winter.  I took two data sets, each from adjacent rounded bumps. By now a cooling slight breeze had picked up and bulbous cloud had appeared from the west.  Away toward the west the profiles of the higher hills were now hidden under cloud but their lower slopes of white were still clearly visible.

Gathering data at the summit of Allt Dolanog

As the Trimble was packed away I headed down toward my inward track and looked out toward Pen y Berth (SJ 081 127) a hill I had visited with Mark only a couple of months ago.  Its conifered upper slopes contrasting with lower slopes of green, all framed by a foreground of dappled bracken and a sky of radiant blue.

Looking across the Afon Efyrnwy to Pen y Berth (SJ 081 127)

Once back at my car I drove out of Dolanog and as my route back home passed over the critical bwlch of Pen y Berth I pulled over and parked at a junction and examined the lay of land.  I chose the spot for Trimble placement and gathered bwlch data which would now give an accurate drop value to the hill whose summit was surveyed two months ago.

Gathering data at the critical bwlch of Pen y Berth

Although not great in height these two hills proved a joy to be out on, and to do so in such pleasant weather was a bonus.

LIDAR image of Ffridd (SJ 084 141)

LIDAR – Postscript

Since visiting these hills full LIDAR coverage is now available.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height and positional data that is now freely available for England and Wales.  Consequently the numerical details for these hills have been analysed using this technique, and where appropriate resulting in the LIDAR height and position being prioritised over that produced by the Trimble GeoXH 6000.

Survey Result:

Ffridd (significant name change)

Summit Height:  295.9m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SJ 08441 14114 (Trimble GeoXH 6000)

Bwlch Height:  266.3m (LIDAR)

Bwlch Grid Reference:  SJ 08281 14699 (LIDAR)

Drop:  29.6m  (Trimble GeoXH 6000 summit and LIDAR bwlch) 

Dominance:  10.01% (Trimble GeoXH 6000 summit and LIDAR bwlch) 
   

Allt Dolanog

Summit Height:  288.5m (converted to OSGM15)

Summit Grid Reference:  SJ 06784 13459

Bwlch Height:  223.4m (converted to OSGM15)

Bwlch Grid Reference:  SJ 06510 14256

Drop:  65.1m 

Dominance:  22.56%

Pen y Berth

Bwlch Height:  153.3m (converted to OSGM15)

Bwlch Grid Reference:  SJ 08679 11702

Drop:  134.2m (converted to OSGM15)  

Dominance:  46.68%

For details on the summit survey of Pen y Berth

For further details please consult the Trimble Survey Spreadsheet click {here}

Mapping Mountains – Trimble Surveys – Y Berwyn

19.10.14  Pen y Berth (SJ 081 127)  

The conifered summit of Pen y Berth (SJ 080 127) off in the distance

Sometimes the seasonal change amongst the hills can be dramatic.  This year the late summer warmth of September was swept away with October’s first winds and then along came the succulent colour.  Today that seasonal change manifested itself in hillsides aglow with yellowed bracken and dark grey rain clouds sweeping eastward pushed along by a strengthening westerly.

The hills for today’s two little wanders had been suggested by Mark who was busy tidying up his Section 30E and 31A Humps.  The first hill Mark wanted to visit was Pen y Berth which is situated just east of Dolanog and rises above the B4382 to the south and the Afon Efyrnwy to the north.

We parked in a lay-by at SJ 072 127 which is large enough to accommodate five or six cars.  The footpath heading north-eastward from the lay-by is on Glyndŵr’s Way and forms part of the 217km (135 mile) long distance walk that starts / finishes in Welshpool and Knighton.

The initial part of our walk was just above the Afon Efyrnwy as it heads eastward to its meeting with the Afon Hafren at the border with England.  At this point the Efyrnwy forms a number of pools well known locally for summer swimming, today its waters bubbled down past fields and hillsides scattered with fallen autumnal leaves.

On part of Glyndŵr's Way as it contours above the Afon Efyrnwy

As we made progress above the river the first of the predicted showers fell upon us, the forecast was for heavy downpours quickly being blown eastward.  Thankfully the rain was only intermittent and as we headed up on open hillside out of the lower growth of trees the rain ceased and was replaced with unseasonably warm sunshine.

Pen y Berth was first listed as part of the Welsh 200m P30 hills that were published on Geoff Crowder’s v-g.me website.  An accompanying note for the hill states ‘Two points of same height’.  This comment was based on the hill having two tops both of which had no spot height on the maps of the time but both with uppermost c 280m ring contours.  Nowadays the Ordnance Survey enlarged Geograph map give each top a 282m spot height.

Autumnal colour as the showers to the west begin to mass

Once on open hillside we followed green ways past yellowed bracken up to a wall which led to a small path heading up to the bwlch between the two tops.  We visited the more easterly one first which is positioned in a copse of deciduous trees and has an attractive uppermost ridge with embedded small rocks breaking out of the ground on its spine.  The Trimble was placed on the point judged to be the highest and gathered five minutes of data.

Approaching the easterly top of Pen y Berth

Gathering data on the easterly top

To our west the shower clouds were massing and as we headed toward the more westerly top the land to our south grew a darkened grey as it was duly swamped with the wet stuff.  The showers looked heavy but as of yet we had survived almost intact and relatively dry.

The westerly top is immersed in conifer plantation with its easterly point having mixed larch, it was this point we concentrated on for a survey.  I’d brought a one metre high pole to fix the Trimble on so it could be elevated above the ground.  This was pushed into the ground at the high point and we waited in the knowledge that the accuracy of 0.1m may not be attained because of the tree coverage.  After waiting ten minutes I inspected the screen and abandoned this point as the figure read 2.3m of accuracy.

The unsuccessful attempt to gather data at the easterly point of the westerly summit

I then positioned the pole in a slight clearing and levelled the top of the pole to the high point we had reached.  This would give a height equivalent to this high point.  Once the accuracy was attained I pressed ‘Log’ and hid in the trees for the five minutes of data collection. 

Aligned to the high point in the conifers the Trimble gathers its data

As the equipment was packed away the next shower skimmed us and the wind blew, it looked as if we would get soaked on our descent but again we were lucky as the heavy shower hit the southern lands and we arrived back at the car and headed off toward Y Byrwydd the next Hump of the day.

Survey Result:

Pen y Berth

Summit Height:  287.5m (converted to OSGM15) (significant height revision) 

Summit Grid Reference:  SJ 08126 12730 (summit relocation confirmed)

Drop:  134.2m (converted to OSGM15)

Dominance:  46.68% (Lesser Dominant status confirmed)

For details on the bwlch survey of Pen y Berth


For further details please consult the Trimble Survey Spreadsheet