Mapping Mountains – Trimble Surveys – Banc Llechwedd Mawr

 

03.09.25  Twyni Mawr (SN 606 938) 

Twyni Mawr (SN 606 938)

Blanks on the map can be interesting to investigate.  These are the places that Ordnance Survey designate in flux, as in the ground they inhabit is unstable.  These include quarries, landfills and other places terra-formed by human interference.  However, they also include places that have not been altered by man’s need to make big holes or bury a lot of stuff in the ground. 

The blank on the map

Nowadays other online mapping show contours for such places, this gives perspective to the lay of land.  Today I was visiting friends and if the weather acted kindly we planned on visiting one of these blanks on the map.  I mention the weather as leaving Welshpool and driving west the cloud base soon closed in with drizzle becoming ever more present.  Approaching the coast this turned into heavy showers with the narrow roads leading to Ynys-las becoming water-logged.  I suppose after an unseasonably warm summer, a bit of rain was a change! 

Extract from the interactive mapping hosted on the WalkLakes website

I was heading to the Searivers Caravan Park, where Eryl and Rita were enjoying a few days relaxation, including coastal walks between what was proving to be a particularly wet spell of weather. 

The Searivers caravan site at Ynys-las

By the time I pulled up outside their home from home the rain was bucketing down, so much so that I ran from the car to the front door and hoped it was opened without delay.  The next hour or so I was very happily settled on a chair, with a mug of tea and assorted biscuits at hand as we caught up with all manner of things, whilst the rain continued to fall.  As time progressed a glimmer of semi-brightness appeared out to sea, this quickly pushed inland and heralded a tempting flash of sunlight as the rain calmed its deluge.  Rita said; ‘right if we’re going to go we need to get ready and make the most of whatever dry spell we have’.  This we did, and soon were walking through the site toward the narrow dead end road and the gate on its opposite side which gives access to the complex of dunes.

Prior to my visit I’d examined this blank on the map via LIDAR, building up the coloured contours until the high point and the connecting bwlch of these dunes was found.  LIDAR gives this point as having 18.4m of drop, so it easily qualifies as a Welsh P15, whilst maps record the name of Twyni Mawr for this area, which is apt as a translation of this can be big dunes. 

LIDAR summit image of Twyni Mawr

Whatever the occasion it’s always good to see Eryl and Rita, whom I’ve shared so much with over the years, especially so with Eryl; including travelling and treks around the Alps, Nepal, Tibet, Vietnam and Cuba, nowadays our ambitions are reduced, but the friendship is still strong. 

Information board at the access to the dunes

Our access to the high point of Twyni Mawr was via a wooden walk way which continues to the coastal sands and the sea beyond; where the walk way crests the dunes a convenient bench had been installed.  Not surprisingly this point gives extensive views out to sea and also inland to what today were cloud enshrouded hills.  Although the view was to be admired the cloud out to sea looked like more showers were on their way, so not lingering I followed Eryl as he started down the walk way whilst suggesting the best way to the high point of the dunes was to cut back using one of many valleys that interweave amongst the dunes.  Eryl had investigated some of these and cautioned that when in them it’s hard to know where exactly you are. 

The wooden walk way heading into the dunes

The path beyond the high point of the wooden walk way

Leaving the walk way we headed into the dunes and accessed the valley directly below the western flank of the high point.  It was here that Eryl stayed, watching me and Rita as we headed the short distance across the valley to the base of the steepening dune.  

The valley leading to the high point of Twyni Mawr.  Photo: Eryl Selly

Heading toward the summit of Twyni Mawr.  Photo: Eryl Selly

I’d brought an umbrella, which is a norm for me even on some higher hills, as if confronted by rain it can shield my camera equipment much better that a Goretex coat, and although it was never used today as whatever rain did come across was never heavy enough to seek protection, it proved an ideal replacement for a walking pole for Rita, who used it to steady herself as we slid ourselves uphill on the steepening sand dune.

Once at the top of the steep bit it was only a short walk on a narrow path across the ridge of the highest dune to its summit.  Here we posed for the customary photographs before continuing on the narrow ridge path back toward where Eryl was patiently waiting for us on the wooden walk way. 

At the summit of Twyni Mawr.  Photo: Rita Selly

Heading back to the caravan the whole adventure had only taken 55 minutes, and we were ever so lucky with the weather as only a skidding light shower had blown across the land whilst on the dunes, which was fortunate considering how heavy the showers had been on my way toward Ynys-las and on my arrival.

We ended the day with a trip into Aberystwyth for a lunchtime meal at the University Art’s Centre before settling down to watch The Roses in the cinema.  It even brightened up for our drive back to Ynys-las and my continued journey to Welshpool.  It proved an excellent day out. 

 

Survey Result: 

 

Twyni Mawr 

Summit Height:  22.8m (LIDAR) (significant height revision)  

Summit Grid Reference:  SN 60614 93828 (LIDAR)

Bwlch Height:  4.4m (LIDAR)

Bwlch Grid Reference:  SN 60576 92484 (LIDAR) 

Drop:  18.4m (LIDAR) (Welsh P15 addition)

Dominance:  80.55% (LIDAR)

 

 

For further details please consult the Trimble Survey Spreadsheet

Mapping Mountains – Trimble Surveys – Drygarn Fawr

 

27.11.22  Pt. 357.3m (SN 995 612) 

November days are to be treasured.  The first frosts linger in chilled mornings with mist enshrouded valleys heralding the near onset of winter.  But November days also give dulled grey skies with misted hill tops.  Usually the latter have hardly a breath of breeze adding a quiet tranquillity to an otherwise dulled scene.  It was such a day today, with the land quiet and autumnal colour still clinging on. 

A grey November day

A walk was planned, more a meeting of good friends with a small hill as accompaniment.  We had an added bonus to find, but this post will concentrate on the hill, which although only having a small amount of prominence gave a good ascent when approaching from its south-east.

I was out with Darrin and Lisa, and Eryl and Rita; as it was Lisa’s birthday celebratory nibbles were also had during the walk.  We met in Trefeglwys before continuing to Llanidloes and then driving southward toward Newbridge on Wye, followed by the minor roads leading to our designated parking spot. 

Heading eastward toward the old house

Although the skies were leaden and dull looking as if they were going to be awash with rain, the forecast gave for dry and brightening conditions.  Even though we were in no rush, the walk only took two hours; leaving the cars for a leisurely stroll across a steep field heading eastward.  This would take us on a circuitous route around the upper part of our small prominence hill before striking upward toward its summit.

Prior to visiting this hill I had examined its numerical data via LIDAR.  Therefore, although tempted to bring the Trimble to at least take a summit data set, I decided to leave this at home and be reliant upon the highly accurate LIDAR summit and bwlch data for its height and position. 

LIDAR image of Pt. 357.3m (SN 995 612)

We had two stops before the summit, one at an old house and the other sitting on rocks in the adjacent field to the summit for chats and nibbles.  Before joining the group at this latter spot I sauntered over to a small pool that was probably only there because of recent rain.  From here I spent a number of minutes admiring the reflection of old trees in the water whilst my friends opened the nibbles. 

Reflected view before celebratory nibbles

After our stop it was only a short distance to the summit, with increasingly good views in all directions, with the bulk of Drum Ddu ahead and the river valley below.  Between the two were moorland ridges and more hills.  It felt good to be out. 

Heading toward the summit of the low prominence hill

Leaving the summit we made our way down to the minor road and from here it was only a short walk back to the cars, with two highly enjoyably leisurely hours on the hill, an excellent way to spend a day. 

 

Survey Result:

 

Pt. 357.3m

Summit Height:  357.3m (LIDAR)

Summit Grid Reference:  SN 99517 61281 (LIDAR)

Bwlch Height:  342.9m (LIDAR)

Bwlch Grid Reference:  SN 99418 61379 LIDAR)

Drop:  14.4m (LIDAR) (Welsh P15 reclassified to Welsh Sub-P15)

Dominance:  4.02% (LIDAR)

 

 

For further details please consult the Trimble Survey Spreadsheet

 

 

 

 

Mapping Mountains – Trimble Surveys – Pumlumon

 

16.07.21  Parc (SN 752 994), Ffridd Bryn Mawr (SN 750 987), Ffridd Cae Crydd (SN 749 976) and Ffridd Eithaf (SN 745 977) 

Ffridd Eithaf (SN 745 977)

There are times when individual walks stand out.  The reasons why are personal to each of us, for me they centre on the unexpected.  This is probably due to having an organised nature to my hill walking and surveying, because of this I usually know the route ahead and what to expect.  Therefore, when the unexpected happens it adds spontaneity to the walk.  Today was such a day.  It proved a magical experience. 

The day was shared in the company of Suzanne, a good friend who lives in Llanidloes.  The forecast gave warm conditions with the temperature nearing 30°, therefore I scrutinised maps for a suitable walk with 3 – 5 hills to visit, and relatively short in length with no more than 6 – 7 miles.  I found a good circuit of five hills just south of Machynlleth that was ideal, with the added bonus that the summit of the last P30 had recently been relocated to an adjacent hill, and both could be Trimbled to confirm or again relocate. 

We left Llanidloes at 7.00am and headed over the mountain road to Machynlleth.  When clear the views from this road extend as far north as Yr Wyddfa, with the immediate surroundings being the ridges of the northern Pumlumon hills.  This view never disappoints.  On the way the road passes Llyn Clywedog, today slithers of mist ebbed against the distinctive profile of Yr Allt, I stopped the car for us to look and savour.  

Llyn Clywedog and the distinctive profile of Yr Allt

As the journey continued I stopped the car on a number of occasions to do likewise, but now we were confronted by the whole of the Dyfi valley enshrouded in mist.  This stretched for miles and lapped against those wonderful northern Pumlumon hills.  At one point it was as if the road abruptly ended and disappeared directly in to the mist.  This unexpected view gave a wonderful start to the day. 

The mountain road leading to Machynlleth

Eventually we pulled ourselves away from the view and drove down in to the mist and through Machynlleth, before continuing to the minor road that wound its way to the start of the walk. 

As we left the car walking back up the narrow road that I had just driven down we were in mist.  The higher we walked the first vestiges of blue sky were occasionally glimpsed out of the ethereal surrounds.  It was as if summer had become alive as the undergrowth beside the lane consisted of a myriad of flowers and greened growth, all delicately dew laden.  Gorse bushes were intertwined with delicate spider webs, whilst singular ones sparkled with their strands holding tear drops of dew.  It was wonderful to just stop and look. 

Gorse bushes laden with dew soaked webs

Leaving the lane we continued on a good track which gained height as it wound its way eastward in to the hills.  By now the sun’s heat was breaking through the mist with the patches of blue sky becoming larger.  Facing east in to the misted sun the undergrowth beside the track took on a silvered sheen as light sparkled against early morning dew, whilst turning to face west with the sun at one’s back this scene altered and the silvered sheen disappeared, it was a trick of light that we marvelled at. 

Suzanne on the start of the track leading to the hills

Just before breaking out of the canopy of mist we spotted a fog bow, which for me is a rarity when on the hill, it floated close to us, a semi-circular arch of mist backed by blue sky.  Beyond was increasing heat. 

We were now above the mist, which still clung to the valley below with the great bulk of the Tarennydd ridge dominating the north-western horizon.  It had been a magical first hour, but now the heat built up and continued to do so during the remainder of the walk. 

Above the mist with the Tarennydd in the background

The summit of our first hill of the day; Parc, was only a short distance away and we left the track to head toward its high point, which is crowned by an attractive rock outcrop.  The Trimble soon had its internal antenna aligned with the highest part of rock and once it was logging data I sat beside Suzanne, below the equipment, in the sunshine and waited for the allotted data to be gathered and stored. 

Gathering data at the summit of Parc

When planning this walk I included the forested top of Ffridd Rhiwlwyfen (SN 757 986) but was unsure of the best way to approach it from Ffridd Bryn Mawr; our second hill of the day.  The view from the summit of Parc gave opportunity to work out a route as we looked directly in to the western bulk of the hill.  Its summit consists of an attractive cone with relatively new conifers planted on it.  One online log did not give encouragement to visit, saying that a chainsaw was now needed to reach its high point.  Guarding this hill were copious amounts of bracken, now matured and no doubt waist and probably shoulder high in places.  We did spot a green track that veered northward and doubled back toward the hill’s upper ridge.  The onward route to this hill looked a hot grind and therefore it was put to one side for a singular expedition in the future.  This left three more hills for us to visit, which in the increasingly warm conditions would be sufficient for the day. 

Ffridd Rhiwlwyfen from the ascent of Ffridd Cae Crydd 

Leaving the summit of Parc we connected with a fence which led down to a good green track which went straight over the connecting bwlch between Parc and Ffridd Bryn Mawr.  Prior to visiting these hills I had examined each with available LIDAR and this was the only bwlch not covered, so it was duly Trimbled. 

LIDAR image of Ffridd Eithaf and Ffridd Cae Crydd

Having assessed the lay of land at the bwlch I decided its critical point was at one of two positions, each about three metres apart on the valley to valley traverse.  Choosing my preferred position I set the Trimble up, waited for it to achieve the 0.1m accuracy level before data should be logged and once activated to gather data, I joined Suzanne who was sitting on a rock beside another green track that veered down toward the watered realm of Llyn Glanmerin. 

Gathering data at the bwlch of Parc

It was a good place to rest, it also felt good that we had dispensed with the ascent of Ffridd Rhiwlwyfen, it was just too warm for this hill.  Hot days on the hill are to be enjoyed, but also respected as heat can be debilitating. 

Ffridd Bryn Mawr (SN 750 987)

Once the Trimble gathered allotted data, I closed it down, packed it away and we continued up a green track toward a gate, which gave access to the upper part of Ffridd Bryn Mawr, today these hills sparkled green in the morning sunshine, luxuriant in their summer growth.  These hills are given over for sheep grazing, and these creatures were still on the hill enjoying munching the grass, but as the day progressed and the intensity of heat increased all but the hardly few were lying in shade. 

Parc from the ascent of Ffridd Bryn Mawr

The summit of Ffridd Bryn Mawr was easy to identify and consists of a small grassed knoll.  As the Trimble gathered data I joined Suzanne who was happy scouting an onward route.  At this stage we did not know whether to use a track that was not marked on my map or a path on the opposing side of the Nant Llyn Gwr Drwg; the steam close to Llyn Glanmerin.  This lake was on view from the first two hills we had visited and we wondered about the best way down to it.  Suzanne spotted a green track leading down to the gravelled track not marked on my map and an easy route to it avoiding rock and bracken that headed toward a gate.  Once the Trimble was packed away we headed down and reached the gravelled track. 

Gathering data at the summit of Ffridd Bryn Mawr

According to the map our onward route was on the eastern side of the stream, the gravelled track was on its western side.  However, this track would give an easy route down toward our next two hills, but as it was not marked on the map we did not know exactly where it went.  Tantalisingly a green path left the gravelled track aiming for the lake, so off we went down to the water’s edge. 

Llyn Glanmerin

What a beautiful place Llyn Glanmerin is. 

The following extract is from The Lakes of Wales by Frank Ward (published in 1931 by Herbert Jenkins):

 

A pretty lake 1 mile south-east from Machynlleth, with alder, spruce, and other trees growing on the banks.  It is formed by the damming of the Rysglog stream, and was made by the late Lord Herbert Vane-Tempest.  It is known locally as Lord Herbert’s Lake, and was originally stocked with brown, Loch Leven, and rainbow trout.  Apparently the rainbows have all disappeared.  Glan-merin belongs to the Marquis of Londonderry.  Fishing is private.

 

We sat beside its waters for quite some time, just looking and chatting and sheltering from the sun.  Swallows darted across the waters, skimming ever lower.  Fish jumped and Water Lilly’s floated.  Suzanne sat in a rowing boat whilst I just relaxed and looked.  It was quite mesmerizing and we almost didn’t walk down to it.  It proved a perfect place to rest, but we still had two hills to visit and the midday heat was quickly approaching. 

A beautiful place to stop and rest

Water Lilly's

Beside Llyn Glanmerin

Leaving the lake we connected with a green track through fern, in its lower section this became a muddied track; this was easily bi-passed though on either side.  The air was heavy with heat and whatever slight breeze the tops afforded soon disappeared as height was lost. 

The green track leading down toward Ffridd Cae Crydd and Ffridd Eithaf

The green track was at least shaded and eventually emerged on to a field that had a robust old barn sitting proudly on the last vestige of greened grass.  Whilst I continued around its western side, Suzanne went inside to investigate and by doing so disturbed a barn owl.  I caught a glimpse as it glided silently down field toward a mature tree.  By the time we headed toward the tree there was no sign of it.  Beyond was the continuation of the stream emerging from the lake, at this point the stream was canopied by small trees.  We were soon sitting in shade beside the stream resting and enjoying a bite to eat.  Behind me through the trees all I could see was increasing warmth, just blue sky, almost iridescent in its hue, a deep blue that radiated ever increasing heat. 

Shelter beside the stream

The view of the heat from the shaded spot beside the stream

The shelter of shade is a wonderful thing, this is rarely necessary in the climate we experience, but today it was sought.  Eventually we left our shaded spot beside the stream and entered the heat, slowly gaining height to a gate and then a green track upward to a small quarried area and then toward a corner of forestry, before which we broke off right and headed toward the summit of Ffridd Cae Crydd.  Not surprisingly we stopped again under a small tree and sat in its shade. 

Heading toward the shade under the tree

It was only a short walk from the small tree to the summit.  This hill’s high point consists of a rocky knoll and having assessed the lay of land I positioned the Trimble atop my rucksack and it was soon quietly beeping away gathering individual datum points. 

Gathering data at the summit of Ffridd Cae Crydd

Just to the west of Ffridd Cae Crydd is Ffridd Eithaf, until recent times the latter was given the status of P30 in the 200m Twmpau list, but LIDAR gives the former as the higher.  The summit heights produced by LIDAR are given below: 

 

Ffridd Cae Crydd:  272.190m 

Ffridd Eithaf:  271.739m 

 

Because of this the listed summit for the P30 was relocated.  Today gave opportunity to survey each with the Trimble GeoXH 6000.  Once data were gathered and stored from the summit of Ffridd Cae Crydd, I closed the Trimble down and we continued westward down to a fence and then up to the summit of Ffridd Eithaf, which is crowned by a quartzite boulder, beside which is a large log hollowed out as a seat. 

Gathering data at the summit of Ffridd Eithaf

Scattered across the summit area were beautiful purple mountain pansies, a delicate flower, miniature compared to their propagated garden variety.  As the upper part of the log was higher than the top of the boulder I placed the Trimble atop my rucksack on the boulder to give it elevation above the log, with its internal antenna aligned to the high point of rock.  After noting the measurement offset it proceeded to gather allotted data. 

Dotted across the summit of Ffridd Eithaf - the beautiful and delicate mountain pansy

Relaxing on the log bench and enjoying the view

With the last data set of the day complete we sat on the log bench, chatted and enjoyed the view down valley to the coast.  We remained there for about 15 minutes.  Our downward route was via Bryn-melyn farm and its connecting track to the valley below.  Beyond the farm we cut a corner following a sheep path and then steeply down to the narrow lane.  Once on the lane we turned right and headed down and back to the awaiting car.  It had been a hot day on the hill, but one full of wonder and rather magical in places. 

 

Survey Result: 

 

Parc

Summit Height:  232.5m (converted to OSGM15)

Summit Grid Reference:  SN 75297 99423

Bwlch Height:  200.6m (converted to OSGM15)

Bwlch Grid Reference:  SN 75150 99131

Drop:  31.9m

Dominance:  13.72%

 

 

Ffridd Bryn Mawr (significant name change)

Summit Height:  238.9m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 75026 98782 (Trimble GeoXH 6000)

Bwlch Height:  196.0m (LIDAR)

Bwlch Grid Reference:  SN 75715 99369 (LIDAR)

Drop:  42.8m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  17.94% (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

 

Ffridd Cae Crydd

Summit Height:  272.3m (converted to OSGM15, average of two Trimble GeoXH 6000 surveys)

Summit Grid Reference:  SN 74910 97692 (Trimble GeoXH 6000) (summit relocation confirmed)

Bwlch Height:  232.8m (LIDAR)

Bwlch Grid Reference:  SN 75107 97628 (LIDAR)

Drop:  39.4m (Trimble GeoXH 6000 summit and LIDAR bwlch) (Welsh Sub-P15 reclassified to 200m Twmpau)

Dominance:  14.49% (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

 

Ffridd Eithaf

Summit Height:  272.2m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 74578 97750 (Trimble GeoXH 6000)

Bwlch Height:  255.7m (LIDAR)

Bwlch Grid Reference:  SN 74763 97683 (LIDAR)

Drop:  16.5m (Trimble GeoXH 6000 summit and LIDAR bwlch) (200m Twmpau deletion)

Dominance:  6.06% (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

 

For further details please consult the Trimble Survey Spreadsheet