Mapping Mountains – Trimble Surveys – Yr Eifl

 

17.09.22  Mynydd Mawr (SH 140 258) 

Mynydd Mawr (SH 140 258) from a previous visit to the hill

As a child my family holidayed at Morfa Nefyn and Edern.  I have a distant memory that during one of these holidays we headed to the end of Pen Llŷn and drove up the concrete road that leads to the summit of Mynydd Mawr.  We could have done this more than once, but my memory only retains small segments from my childhood and even these only give me the semblance of one distant childhood visit. 

For many years we spent our holidays in this house in Morfa Nefyn

It would be many years later when I next visited this hill and since then I have been back to survey its summit and visited again with my brother.  This time I was with my aunt, cousin and brother.  We were staying in Nantlle and a road trip taking in the beauty of the Llŷn had been suggested. 

The view from the coast at Nefyn

It is all too easy to accept the land one lives in; after all it is the land one is used to.  However, heading from Welshpool to Nantlle my aunt and cousin both marvelled at the beauty of the land we were travelling through.  I had done this journey countless times over many years and although I would like to think my eye is still appreciative of this land, there is no doubt an acceptance on my part, as for me it is a constant.  Seeing it with new eyes through the experience of my aunt and cousin gave me added appreciation of just how beautiful this land is and by that fact, how fortunate I am to live where I do.

On our way down Pen Llŷn we visited the old houses where we holidayed, reminiscing on times now long gone.  A multitude of narrowing lanes lead west down the Llŷn toward the paved road that starts its way up Mynydd Mawr, this soon turns in to a concrete road ending at the top of the hill, where a levelled section gives adequate parking for a number of cars.  We weren’t the only ones heading up this hill, there were a few walkers on the manicured green paths, but in the main it was the convenience of a car that brought people here. 

Looking inland toward the high Eryri peaks

Having parked I sauntered off to stand on the high point and before joining Bryn, Shirley and Julie I took a few minutes to look inland toward the higher peaks of Eryri which were framed by a sweeping coastline.  It was a stunning view, whilst behind the great swathe of the Irish Sea dominated, following this around and the bulk of Ynys Enlli looked back as a darkened silhouette, whilst to its right a slight greyed outline of the distant Wicklow hills, south of Dublin could just be picked out.

Leaving the summit I joined Bryn, Shirl and Julie on the series of steps leading down with the distant Ynys Enlli ahead.  We followed these for a while before stopping, all round was the expanse of sea, a huge blue mass stretching to the horizon. 

Looking out toward Ynys Enlli

We stayed looking out to sea for quite some time and once heading back up the steps we veered rightward to join one of the paths leading up the hill toward the top, this soon led us back to the car.  It’s always good to visit this summit, be it by foot or car.  It signifies an end of land and if the weather conditions are favourable, as they were today, it can give a dramatic element to this beautiful land that we live in. 

 

Survey Result:

 

Mynydd Mawr

Summit Height:  160.0m (converted to OSGM15, from previous Trimble GeoXH 6000 survey)

Summit Grid Reference:  SH 14021 25869 (from previous Trimble GeoXH 6000 survey)

Bwlch Height:  64m (spot height)

Bwlch Grid Reference:  SH 14952 26292 (spot height)

Drop:  96m (Trimble GeoXH 6000 summit and spot height bwlch)

Dominance:  60.00% (Trimble GeoXH 6000 summit and spot height bwlch)

 

 

For details on the survey of Mynydd Mawr

For details on the 2^nd visit to Mynydd Mawr

 

For further details please consult the Trimble Survey Spreadsheet

 

 

 

Mapping Mountains – Trimble Surveys – Yr Eifl

11.04.21  Mynydd Mawr (SH 140 258) 

Mynydd Mawr (SH 140 258) from my previous visit to the hill

The last time I visited Mynydd Mawr was in the early life of my Trimble when accompanied by Aled and Mark we visited the hill and I surveyed its summit.  On that day we chased daylight hours as this was in Decemeber 2014 and after descending the hill we walked up the adjacent Mynydd y Gwyddel.  Here we stayed watching as the last embers of daylight sank behind the blackened profile of Ynys Enlli giving a beautiful sun set. 

Watching the sun set after my previous visit to Mynydd Mawr

Today was at contrast as I was out with my brother; Bryn, touring the Llŷn and investigating its minor roads.  We had no definite destination, just to get out whilst enjoying the company that Covid had starved us of over the last year or so. 

Although we had no definite destination I had mentioned driving up Mynydd Mawr, but again we just aimed west and carried on.  By doing this we found ourselves at the base of the hill, and once here we were definitely going to aim for its summit. 

The weather conditions were also at contrast to my last visit, this as described above gave late afternoon winter light before we stood and quietly watched the sun set.  Today showers were forecast with a mixture of sleet and snow.  Before setting off we had watched large flakes of snow fall for an hour or so, cloaking near hills.  By the time I drove up the concrete access road leading to the top of Mynydd Mawr the snow had quickly thawed from this part of the world and glimmers of sun and little breeze warmed us as we got out of the car. 

The end of the concrete road

Bryn headed off toward a rocky knoll to look out to sea, whilst I scampered up to the high point of the hill.  Away to our west and out to sea huge shower clouds were massing.  Beyond Ynys Enlli, which today was greyed with slithers of spring green on its slopes, whitened winter showers were also breaking out across the sea.  But the one that dominated was blackened grey with a whitened cap; this took up much of our immediate attention.  It massed out to sea forever heading eastward directly toward the end point of the Llŷn. 

Gathering data at the summit of Mynydd Mawr during my previous visit

Same place, but different weather conditions

My brother called over as I headed his way from the summit, he just stood and pointed out to sea toward the increasingly large darkened mass of wintery shower cloud.  We knew it was heading directly toward us as by the time I had sauntered a little lower to look back up and take a few photographs, and then having re-joined Bryn, the wind had picked up and the last vestiges of sunlight were now overtaken by the darkened mass. 

Darkened shower clouds mass

We looked out to sea one last time and headed toward the car.  Driving down the concrete access road the first large drops of rain hit the windscreen.  By the time we were back on the narrow roads it was sleeting and the onward journey involved watching as huge showers took over the sky.  These were accentuated as small parts of the land were still bathed in sunshine, whilst seemingly all other land was greyed and covered in wet murk. 

It was a dramatic journey back to Nantlle watching the ever changing sky as large shower clouds obliterated the landscape.  However, it had been a good road trip and especially as we’d made the summit of Mynydd Mawr before the sleet had set in. 

 

Survey Result: 

 

Mynydd Mawr

Summit Height:  160.0m (converted to OSGM15, from previous Trimble GeoXH 6000 survey)

Summit Grid Reference:  SH 14021 25869 (from previous Trimble GeoXH 6000 survey)

Bwlch Height:  64m (spot height)

Bwlch Grid Reference:  SH 14952 26292 (spot height)

Drop:  96m (Trimble GeoXH 6000 summit and spot height bwlch)

Dominance:  60.00% (Trimble GeoXH 6000 summit and spot height bwlch)

 

 

For details on the survey of Mynydd Mawr

For details on the 3^rd visit to Mynydd Mawr

 

For further details please consult the Trimble Survey Spreadsheet

 

  

Mapping Mountains – Trimble Surveys – Craig Berwyn

02.09.17  Garnedd Wen (SJ 131 311) and Mynydd Mawr (SJ 133 286)

Mynydd Mawr (SJ 133 286)

Having been away from the hills for two months I wanted a fairly easy walk to ease my way back on to them and combining Garnedd Wen with Mynydd Mawr was a perfect way for my right knee to recuperate without being tested too much.

A narrow road heads eastward from Maen Gwynedd toward Llanarmon Dyffryn Ceiriog and the grass verge close to the connecting bwlch between the two hills proved an ideal parking spot.

I set off at 8.30am just as the early chilled morning gave way to the first warmth of the day.  It felt good to be back on the hills amongst quiet surrounds with a radiant blue sky above and just a breath of breeze adding to the beauty of patch worked green fields which were dotted in white sheep smothering the land.

A vehicle track on the hillside soon gave way to a closely cropped grassy field which led up toward the summit of my first of two hills of the day; Garnedd Wen, which is listed as a 400m Sub-Pedwar.  Skirting the summit I headed down toward the hill’s critical bwlch and aimed for a gate giving access on to moorland and a track heading toward a fence that crosses the bwlch in a hill to hill direction.  After assessing the lay of land from a number of directions I decided that one of the fence posts was as good as any to be declared the position of this hill’s critical bwlch and set the Trimble up accordingly.

As the Trimble gathered its customary five minutes of data I stood back and admired the main Berwyn ridge which from this viewpoint butted against the lay of land as it blocks the course of west to east ridges, immediately in front was the continuation of steep land toward the ridge leading to Mynydd Tarw, however tempting this was I realised that a gentle walk was required to accustom my knee to the rigours of hill walking and over ambitious plans may prove detrimental in the long term.

The main Berwyn ridge

Gathering data at the critical bwlch of Garnedd Wen

Y Garn (SJ 080 272)

With the Trimble packed away I headed to the summit of Garnedd Wen where the remains of quartz rocks were jumbled together overlooking the greened and pleasing slopes of Mynydd Mawr, a marvellous scene to look at for someone who has been devoid of mountain views for the last two months.

Mynydd Mawr from the quarzt rocks atop Garnedd Wen

I again positioned the Trimble on a fence post having judged the land at its base to be the summit of the hill, this time improvising and laying my Goretex coat on the post as a part of the barb wired fence had been hammered in to its top, by placing the Trimble on top of my coat it protected its underside and elevated it above its immediate surrounds, once the offset was measured with a steel tape it bleeped away gathering its 300 allocated datum points.

The gentle north-western slopes of Mynydd Mawr

Gathering data at the summit of Garnedd Wen

By now the first clouds had bubbled up in an otherwise spotless blue sky, and by the time I retraced my steps back down the hill to the narrow road more clouds had appeared.  After taking a data set at one of two possible bwlch positions of Mynydd Mawr I slowly plodded up beside a fence toward its summit, the north-easterly ridge of this hill is relatively broad and long, and gave chance for my mind to wander as height was slowly gained.

The summit of Mynydd Mawr is crowned by a triangulation pillar with elevated land approximately 5 metres to its west and 19 metres to its east, with the high point of each on exposed rock that forms a small rock crest which is more prominent on the eastern side.  I took data sets from each high point before setting off back on my inward route.

Gathering data from the point 5 metres west of the trig pillar on Mynydd Mawr

Gathering data from the point 19 metres east of the trig pillar on Mynydd Mawr

The Trimble set-up position at the summit of Mynyd Mawr with the trig pillar in the background

Following the fence line back down the hill the profile of Y Gurn looked forever majestic, a wonderful hill considering its relatively lowly height.  All that remained was to take a second data set from the continuation of the land that makes up the bwlch of Mynydd Mawr, this time from the position that I considered to be the critical point, as this was beside a gate that led to the narrow road where my car was parked it was a convenient place to end the day’s surveying.

Y Gurn (SJ 184 293)

Gathering data at the critical bwlch of Mynydd Mawr

The walk proved ideal in length to test my recently operated on right knee, and was also ideal to re-accustom myself to the hills and using the Trimble after a two month layoff.  

Survey Result:

Garnedd Wen 

Summit Height:  496.0m (converted to OSGM15) 

 

Summit Grid Reference:  SJ 13181 31156

Bwlch Height:  472.3m (converted to OSGM15)

Bwlch Grid Reference:  SJ 13046 31401

Drop:  23.8m 

Dominance:  4.79%

Mynydd Mawr

Summit Height:  534.7m (converted to OSGM15)  

Summit Grid Reference:  SJ 13306 28624

Bwlch Height:  430.0m (converted to OSGM15)

Bwlch Grid Reference:  SJ 14135 30581

Drop:  104.6m 

Dominance:  19.57%

For further details please consult the Trimble Survey Spreadsheet

Mapping Mountains – Trimble Surveys – Yr Eifl

28.12.14  Mynydd Mawr (SH 140 258) and Mynydd y Gwyddel (SH 141 251)   

Mynydd Mawr (SH 140 258)

At the end of Wales the Pen Llŷn (Lleyn Peninsula) butts down steeply to the sea and looks out toward Ynys Enlli (Bardsey Island) which in medieval times was a major centre of pilgrimage.  The land at the north-western tip of Wales is dotted with small hills, many excellent in nature and with coastal views it reminds one of the Dingle peninsula in Ireland, albeit slightly less dramatic.  However, there is a feeling of gentle solitude to these hills where land and sea meet.

Having visited Clip y Gylfinhir in the morning and relaxed with a panini in one of the pubs in Aberdaron we headed toward the western fringes of the Llŷn and the car park at the base of Mynydd Mawr.

The summit of Mynydd Mawr was used as a lookout station during the 2^nd World War and the access road to the building that remains positioned on the summit is maintained and contours its way up the hill.  As Mark got his boots on I slowly plodded up this road as I wanted to get two data sets, one from beside the small building and another on a high point a hundred metres or so away.

The first of these two points has an embedded boulder at its highest point, as the Trimble gathered its allotted five minutes of data Mark and Aled joined me.  Soon it was placed on a point close to the building for its second data set.

Gathering data at the summit of Mynydd Mawr

Once the second data set had been collected we found a spot on the opposite side of a wall, overlooking the steep drop into the sea and did an interview with the digi-camera with Mark filming whilst Aled and I gave details to a forthcoming Europeaklist booklet that is due for publication in January / February 2015.

As the filming wrapped up we headed south-east away from the road and down to the connecting bwlch with Mynydd y Gwyddel.  During the descent Ynys Enlli was always there, in vision, a darkened silhouette against the lowering western sun, aloof in bulk it stood out to sea, a haven for pilgrimage from past religious to modern Marilyn bagger.

Heading toward the bwlch of Mynydd y Gwyddel

Although small in area the connecting bwlch between Mynydd Mawr and Mynydd y Gwyddel proved difficult to pinpoint as it had a high stone wall positioned in an earthen embankment cutting the valley to valley traverse.  We each assessed where we thought the critical bwlch lay and as Mark and Aled made their way up Mynydd y Gwyddel I climbed up the embankment and over a fence into a close cropped field where we had judged the critical bwlch to be situated.  I chose a spot a few metres from a caravan and waited for the five minutes of data to be collected before joining Mark and Aled on the summit.

Gathering data at the bwlch of Mynydd y Gwyddel

As I approached the summit I spotted Mark and Aled sitting about 50 metres from the high point looking out to sea as the sun shone bright.  Next to the high point sat a couple who were soaking in the view and who looked as if they were their long term until the sun set.  I said ‘Hi’ and apologetically explained what I wanted to do, they very kindly moved lower down the hill and I had the summit to myself to set the Trimble up and gather the all-important data.

Gathering data at the summit of Mynydd y Gwyddel

Just as the last of the 300 points of data were collected Aled stood up and put his rucksack on and walked toward me, Mark soon joined and we stood beside the high point of the hill and looked out to Ynys Enlli as the sun sank lower radiating its stream of golden colour across the sea.  Although this was a beautiful image and one that held our attention for the next forty minutes, it was the view farther west that caught us, as a slender line of hills were on show; the Wicklow Mountains in Ireland.

Between cloud and sea - the Wicklow Mountains

We’d seen the Isle of Man from the summit of Mynydd Mawr and squinting across the sea we thought that some shape of land could just be discerned, but as the sun sank lower the becalmed conditions of light now gave us a cascade of hills lined up south of Dublin.  I hadn’t seen the Wicklow Mountains from Wales for a number of years and this brought back memories of when I was on Bera Mawr in the Carneddau with Ed and we looked out from a snow bound hill across the Irish Sea to Ireland.  This was at a time when I was visiting Ireland regularly and I had just completed a 28 day trip taking in 101 of the 2,000ft hills.  At that time I knew the Wicklow Mountains quite well and as I stood on top of Bera Mawr with Ed, the clarity of visibility was so good that I could pick out individual hills and name them.  Today the outline of these hills were not as vivid as when I saw them with Ed, but Mark, Aled and I stood for a number of minutes looking toward their outline.

The Wicklow Mountains on the western horizon

We were on the verge of departing to head toward the next hill when up sauntered Asha Pond and Clare Richards, both originated from Australia and are now living in London.  By the time we had introduced ourselves and chatted the sun had sank lower and was casting magical light on the land.  Soon we were joined by Guto Thomas, a local farmer who works the land close to Mynydd Rhiw and who is a member of the Bardsey Island Trust.

We were joined on the summit by Asha Pond and Clare Richards

By now the light had dimmed and a chill heralding night had started to ebb onto proceedings, but the sun kept its captivation as it slowly sank ever seaward.  We all stood chattering away and looking west as the sun crept into a thin strip of layered cloud with light emanating out.

Slowly sinking seaward as the chill of the night set in

Sun setting beyond Ynys Enlli

To be here, at the end of Wales, on such a lovely day, with an unexpected chance encounter and watching the sun set next to Ynys Enlli was quite a magical experience. 

I’ll leave you with a few uncaptioned images as the light faded and the sun disappeared.

Survey Result:

Mynydd Mawr

Summit Height:  160.0m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 14021 25869 (Trimble GeoXH 6000)

Bwlch Height:  64m (spot height)

Bwlch Grid Reference:  SH 14952 26292 (spot height)

Drop:  96m (Trimble GeoXH 6000 summit and spot height bwlch)

Dominance:  60.00% (Trimble GeoXH 6000 summit and spot height bwlch) 

Mynydd y Gwyddel

Summit Height:  97.4m (converted to OSGM15)

Summit Grid Reference:  SH 14183 25164

Bwlch Height:  74.4m (converted to OSGM15)

Bwlch Grid Reference:  SH 14238 25454

Drop:  23.0m

Dominance:  23.63%

 

  

For details on the 2^nd visit to Mynydd Mawr

For details on the 3^rd visit to Mynydd Mawr

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

Mapping Mountains – Trimble Surveys – Moel Hebog

24/25 / 26.12.13  Search for the critical bwlch of Mynydd Mawr (SH 539 546)

Mynydd Mawr (SH 539 546) is listed as a Marilyn, Hump, Hewitt, Nuttall, Sim, 600m Twmpau, Welsh Highland P15 and a Dominant hill with 462m of drop and its critical bwlch listed at SH 558 539.  The position of this bwlch had long intrigued me, as the more I studied the map, more possible positions for it emerged.  Over three days I investigated a number of areas and took data at six different positions.  The only position that was visually dismissed is the current listed one at SH 558 539.

The position for the critical bwlch is problematic due to the land between Mynydd Mawr and its parent hill; Trum y Ddysgl (SH 544 516) now having a reservoir placed on it.  This reservoir is Llyn y Dywarchen, and to complicate matters, the reservoir was once a natural lake and when enlarged it eventually became two lakes with the addition of the crescent shaped Bwlch-y-Moch, each was connected by a strip of water.  The northerly of these two lakes no longer exists and is a reed infested wet land that descends from the earthen embankment at SH 561 535 to the old breached dam at SH 556 539.

My search began in the darkening hours of Christmas Eve with five minutes of data collected at the low point of the hill to hill traverse between Mynydd Mawr and Trum y Ddysgl.  This low point is now on a road at SH 55866 53334 and below one of the stone dams of the lake.  I placed the Trimble on the grass verge beside the road and hoped no car would run it over.  This point is where a 232m spot height appears on the Ordnance Survey enlarged mapping on the Geograph website.

The Trimble beside the road at SH 558 533 beneath the main dam of Llyn y Dywarchen.

At 8.10am the following morning before the parsnips had been cooked I was back beside the lake gathering data on a concrete path that is part of the headwall of the dam at SH 55884 53342.

The concrete path that crosses the outflow of Llyn y Dywarchen above the stone head wall of the main dam.

After visiting the critical bwlch and summit of Bryn Gwyn (SH 556 534) I headed toward another dam at SH 56091 53229 and gathered more data.  This dam is smaller than the main one at SH 558 533.  The Trimble was placed on the dam wall and not on the thick wooden sleepers that formed a path over the outflow as this point was judged to be below the lakes water level.

Gathering data on the dam at SH 560 532 with Mynydd Mawr and Y Garreg in the background.

My last point for the morning’s data gathering before unwrapping Santa’s pressies was on what might be the natural bwlch.  This is an extensive bog with its high point at SH 563 530.  As the Trimble was achieving its 0.1m accuracy before the time when the screen is pressed to start gathering data, the sky toward the south started to close in and envelop the hills with ominous looking showers.  As the accuracy was achieved and the screen pressed the rain was falling and waterproofs were quickly put on.

 The walk back through the bog, over a field and down to the road and up to the car was a soggy squelch.

The weather quickly closed in whilst at the only natural bwlch that remains; SH 563 530.

I now needed to investigate the northern section of Llyn y Dywarchen, and if necessary venture to where the critical bwlch is currently listed.  The indulgence of Christmas was weighing heavily as I made my way around the northern section of the lake.  Surprisingly I wasn’t the first to be out beside the lake on Boxing Day morning as a photographer and assistant were quietly going about their business as dawn was breaking.  The far side of the lake now has an earthen embankment where once the water channel connecting Llyn y Dywarchen with the second lake of Bwlch-y-Moch once existed.

I took data at the low point of the earthen embankment (SH 56160 53573) close to where a 236m spot height appears on the Ordnance Survey enlarged mapping on the Geograph website.

The earthen embankment at SH 561 535.

The Trimble now needed to go for a swim, so I placed it as close to the surface of the water as I risked and gathered more data to establish the height of the surface water.  It rested snuggly on a rock as water lapped beside it.  Every minute or so I took a glance toward it and hoped it hadn’t slowly slipped in to the lagoon.

The Trimble placed on a rock about 2cm above the surface water of Llyn y Dywarchen.

This was the sixth point I had gathered data from as I tried to pinpoint the critical bwlch position of Mynydd Mawr.  I only had one more place to investigate and this was the land between the earthen embankment and where the critical bwlch is currently listed at SH 558 539.  I’d looked down on this land from the summit of Y Garreg two days ago and had thought the land descended from the lake toward the old dam wall at SH 556 539.  However, if the land went up from the earthen embankment toward a high point at approximately SH 561 537 it would mean this was a contender for critical bwlch position.

From the vantage point of the earthen embankment the land to the north looked as if it was descending, if true this would confirm the water drainage as indicated on larger scale Ordnance Survey maps.  I walked a few hundred metres on the western side of what was once the lake known as Bwlch-y-Moch.  To my eye the ground was descending, I then ventured in to the bottom, reedy land and looked back to the earthen embankment; the land seemed to be going up to the bottom of the embankment.  Looking back to the north-west the swing of land heading toward the old dam at SH 556 539 looked as if it was also consistently descending.  Although eyesight alone is not ideal to judge gently descending land, something that was definite is that this land is lower than the surface water in Llyn y Dywarchen.  Satisfied that I’d achieved as much as I could with the equipment at hand I headed back to the car and the prospect of a walk on the beach followed by Boxing Day bubble and squeak.

Beside Llyn y Dywarchen.

There seems to be two current options for a natural bwlch connecting Mynydd Mawr to its parent hill.  One was visually dismissed as being lower than the level of surface water in Llyn y Dywarchen, whilst the other is higher and is a natural connecting bwlch.  But although the land at SH 563 530 is a natural bwlch, is it the natural bwlch or did a lower natural bwlch exist near the main dam wall at approximately SH 558 533 or near the earthen embankment at approximately SH 561 535?  This is hard to answer, but there is only one inflow in to this lake from a point that is a bwlch between Mynydd Mawr and its parent hill, this is at SH 563 530.  All other current inflows are either coming down from adjacent hillsides or from the old leat that once straddled the road on an aqueduct and fed water towards Beddgelert.  The old stone stanchions for this aqueduct are still present either side of the high point of this road.  The present direction of this water has been reversed since the aqueduct no longer exists. 

If another inflow existed it would be an indicator toward where the possible old critical bwlch once lay.  However, if one did exist it may now be under the raised waters of the lake.  But as the land at SH 563 530 is higher than the surface water of the lake it implies that the reservoir has been constructed over the old critical bwlch.  In cases like this, when the natural critical bwlch is thought to be under the waters of a reservoir the surface water of the lake is deemed as the height of the bwlch. 

Postscript: 

Since the bwlch survey of this hill 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 this hill has been analysed using this technique, resulting in the LIDAR height and position being prioritised.  The full details for the hill are given in the 7th option below.

Survey Result:

Mynydd Mawr – bwlch 1^st option – low point on road below dam wall

Height:  231.9m (converted to OSGM15)

Grid Reference:  SH 55866 53334

Mynydd Mawr – bwlch 2^nd option – concrete path over stream on dam wall

Height:  235.0m (converted to OSGM15)

Grid Reference:  SH 55884 53342

Mynydd Mawr – bwlch 3^rd option – small dam wall

Height:  235.1m (converted to OSGM15)

Grid Reference:  SH 56090 53229

Mynydd Mawr – bwlch 4^th option - natural ground

Height:  238.0m (converted to OSGM15)

Grid Reference:  SH 56373 53017

Mynydd Mawr – bwlch 5^th option – earthen dam

Height:  235.6m (converted to OSGM15)

Grid Reference:  SH 56160 53573

Mynydd Mawr – bwlch 6^th option – surface water level

Height:  234.7m (converted to OSGM15)

Grid Reference:  SH 56154 53572

Mynydd Mawr – bwlch 7^th option - LIDAR

Summit Height:  697.6m (LIDAR)

Summit Grid Reference:  SH 53971 54692 (LIDAR)

Bwlch Height:  234.1m (LIDAR)

Bwlch Grid Reference:  SH 56156 53605 (LIDAR)

Drop:  463.5m (LIDAR)

Dominance:  66.44% (LIDAR)

For further details please consult the Trimble survey spreadsheet click {here}