Mapping Mountains – Trimble Surveys – Pumlumon

 

22.11.20  Moel y Llyn (SN 710 914), Moel y Llyn (SN 712 916), Pt. 508.8m (SN 716 914), Pt. 510.6m (SN 717 912), Banc Bwlch y Garreg (SN 729 918), Pt. 511.4m (SN 733 917), Esgair Fraith (SN 738 918) and Bryn Mawr (SN 723 906)

Moel y Llyn (SN 712 916)

This article could be entitled In Praise of Wellies.  For me, this footwear is a necessity once autumnal months set in and then progress in to winter.  Although my winter conversion from standard walking boots to the welly happened many years ago, it is only after I purchased the Trimble GeoXH 6000 that their benefits have been truly felt.  These benefits mainly consist of standing ankle deep in bog as the Trimble is gathering data at a bwlch, and today this was in evidence and as I did so, I wondered if I would even contemplate doing something similar in standard walking boots, my conclusion; probably not. 

Today I was out with Aled, we met in Machynlleth and then travelled toward Aberystwyth, turning off the main road in Tal-y-bont and following the narrow mountain road toward Nant y Moch Reservoir.  Our hills were positioned to the north with an extra hill tagged on at the end of the walk to the immediate south of the road if time and inclination permitted. 

We were walking by 8.20am across the bog just below the road and then gaining height beside an old boundary that contoured the adjacent hillside and headed west.  The conditions were ideal, with just a light breeze that brought a chilled feeling to the early morning, and with clear visibility and high cloud. 

The old boundary soon turned in to a path cutting through a rocked rib and aiming toward another good path that ascends from one of the farms in the valley below.  This now led up to the bwlch between Moel y Llyn to the west and another P30 to the east. 

The northern section of these hills were planted in conifers many years ago and as we debated where the critical point of the bwlch lay, two trail riders roared up the track that cuts a swathe up the periphery of the forest.  We stopped and chatted with them for a few minutes before they headed off on a minor track through the trees.  This left me to set the Trimble up and wait for it to gather its allotted data. 

Gathering data at the bwlch of Banc Bwlch y Garreg

Moel y Llyn is a fine hill; it consists of a number of tops, two of which have relatively large ancient cairns that have been remodelled to incorporate neat modern-day hill cairns.  One of these is the high point of the hill, the other is to its south and it was this lower summit that we now aimed for.  Once there we debated where the Trimble should be set up, as the rocks that incorporate the ancient cairn can now justifiably be thought of as a part of the hill, we therefore set the Trimble up at the base of the modern cairn and left it gathering its individual data points for six minutes. 

The higher of the Moel y Llyn summits

Between this summit and the higher is an attractive small lake and it is close to here that the bwlch for the lower hill is situated.  As we walked the short distance toward it, flashes of light illuminated the higher summit.  Sunlight on the hill at this time of year is always appealing; it accentuates the almost bleached moor and reed grass highlighting its delicate yellowed shade.  Light and shade add depth to any landscape, and this morning I stood for a few moments captivated by the scene of lake, rocky summit and late autumnal colour. 

Llyn Moel y Llyn

Looking back at the lower of the two Moel y Llyn summits that were surveyed

Once the bwlch had been Trimbled we headed up to the highest summit of Moel y Llyn, this again consists of a large ancient cairn that has now been remodelled to incorporate a modern neat cairn with the added indulgence of a near triangulation pillar on it.  Having chosen the spot for Trimble placement I set the equipment up and sat behind the cairn with Aled until the allotted five minutes of data were gathered and stored. 

Nearing the summit of Moel y Llyn

Gathering data at the summit of Moel y Llyn

Our route now headed east following the edge of the northern conifer plantation surveying each summit and bwlch as we did so.  Our next point to survey was the summit of a 511m map heighted hill.  At one time this vied for the summit of the qualifying P30, but it was usurped a number of years ago by its adjacent top.  The first summit consists of moor grass and after it had been surveyed we headed down to its connecting bwlch which consists of a large flattish bog.  Although wet in places it was nowhere near as bad as what we encountered later in the walk, and once we had assessed the lay of land a point for Trimble placement was chosen and the allotted data gathered and stored. 

Banc Bwlch y Garreg (SN 729 918)

Only a short ascent followed to the summit of the qualifying P30 and as I set the Trimble up on its high point I looked further east to the continuation of our route.  We had at least three further hills to visit and survey and the edge of the forestry would lead toward the first two of these.  I appreciated the time spent when the Trimble gathered its allotted data, as this gave me a few minutes to rest and recuperate, although all too quickly it was time to set off and head toward sheep paths through the tussock grass that gave a semblance of semi-decent underfoot conditions. 

Gathering data at the summit of Pt. 510.6m (SN 717 912)

The next point to survey was the bwlch connecting our last hill to the higher Banc Bwlch y Garreg and this was placed in a large tussock laden bog.  As I got to grips with the tussocks Aled made a detour around the bog to get on to drier land to its east.  During this he directed me to the lowest fence post that indicated where the critical point of this bwlch may lie.  I was on ground just to the north of this fence in a section of land where conifers had not been planted, or if they had, they had become water laden many years ago.  The whole place consisted of large tussocks and standing water and I spent an inordinate amount of time waiting for the Trimble to gather its data whilst standing ankle deep in water.  Walking boots would not have been appropriate and it would have been difficult to survey such a bwlch if not wearing wellies. 

Heading toward the next bwlch

Gathering data at the bwlch of Pt. 510.6m (SN 717 912)

It was a slow plod to the summit of Banc Bwlch y Garreg, as we neared its high point we each looked in to the adjacent conifers as LIDAR gives the high point of this hill approximately 19 metres in to the trees, this is a rogue summit as LIDAR is prone to give on occasion in forestry.  All land headed down from the adjacent fence in to the conifers and therefore I set the Trimble up on the summit that is easily identified and which is free of the conifer infestation and headed the short distance to where Aled was sitting and waited for the summit data to be gathered. 

Heading toward the summit of Banc Bwlch y Garreg

Gathering data at the summit of Banc Bwlch y Garreg

We were making good progress and had two summits remaining to visit, with a third as an extra to tag on at the end of the walk if wanted.  The next hill was further east and as its bwlch was to the north of the ridge fence amongst unsavoury looking land and had been LIDARed by Aled, this was bi-passed in favour of its summit.  The low point of the land between consisted of another bog but once this was delicately stepped through all that remained was the steepening slope leading up to its top.  The section of forest to the north of the ridge fence taking in the high point of this hill has recently been felled and the summit of the hill was over the fence amongst the debris of felled forestry. 

Banc Bwlch y Garreg from its adjacent easterly top

By now I was feeling tired and knew that one more hill would be sufficient for my days exploits.  Therefore, once the Trimble was set up and after it had gathered its allotted data we headed down toward a vehicle track that in time would be our way back out from the hills, but before this we headed up the same track toward the summit of Esgair Fraith, which has a map spot height of 499m. 

Heading down toward the track with the forested hill of Esgair Fraith in the background

We soon left the main forest track and veered right on to a narrower track that headed up in to a clear section of land free of forestry where the summit of Esgair Fraith is positioned.  This hill has two mounds vying for its high point, the one further north is the higher, and this is still thankfully free of trees.  The Trimble proceeded to gather ten minutes of data from the summit and I was thankful for the rest. 

Aled approaching the summit of Esgair Fraith

Gathering data at the summit of Esgair Fraith

Once the Trimble was packed away we retraced our inward route back across the lower mound and down to the main forest track which in time led us all the way back to the awaiting car. 

Heading back toward the track

On our way down the track I flagged down a farm vehicle and Aled proceeded to ask about names of near hills.  The farmer grazed land close to Llyn Dwfn and Llyn Conach; this is wild and rough land, and he confirmed many names and told us about the old estate that was sold to the Forestry Commission.  As we neared the car the adjacent hillside was aglow with the last flickers of sunlight, this only lasted a few minutes, but it was a welcome addition at the end of a day on the hill. 

Late afternoon light

However, there was one last hill to contemplate; the 489m map heighted Bryn Mawr.  I knew I wouldn’t be heading up it, but after a quick instruction on how to operate the Trimble, Aled shot up it as I remained at the car and got changed.  Thirty minutes after leaving the car he was back at it and he had also gathered data from the summit. 

It had been another good day on the hill with some beautiful late autumnal light and in all eight summits Trimbled. 

 

Survey Result: 

 

Moel y Llyn  

Summit Height:  513.0m (converted to OSGM15)

Summit Grid Reference:  SN 71075 91418

Bwlch Height:  504.6m (converted to OSGM15)

Bwlch Grid Reference:  SN 71113 91558

Drop:  8.4m

Dominance:  1.63%

 

 

Moel y Llyn  

Summit Height:  521.1m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 71264 91689 (Trimble GeoXH 6000)

Bwlch Height:  c 417m (interpolation)

Bwlch Grid Reference:  SN 75214 92896 (interpolation)

Drop:  104.1m (Trimble GeoXH 6000 summit and interpolated bwlch)

Dominance:  19.97% (Trimble GeoXH 6000 summit and interpolated bwlch)

 

 

Pt. 508.8m  

Summit Height:  508.8m (converted to OSGM15)

Summit Grid Reference:  SN 71666 91458

Bwlch Height:  498.8m (converted to OSGM15)

Bwlch Grid Reference:  SN 71738 91396

Drop:  10.0m

Dominance:  1.97%

 

 

Pt. 510.6m  

Summit Height:  510.6m (converted to OSGM15)

Summit Grid Reference:  SN 71749 91285

Bwlch Height:  476.7m (converted to OSGM15)

Bwlch Grid Reference:  SN 72327 91576

Drop:  33.9m

Dominance:  6.63%

 

 

Banc Bwlch y Garreg  

Summit Height:  520.0m (converted to OSGM15)

Summit Grid Reference:  SN 72977 91812

Bwlch Height:  466.3m (converted to OSGM15)

Bwlch Grid Reference:  SN 71556 91588

Drop:  53.7m

Dominance:  10.34%

 

 

Pt. 511.4m  

Summit Height:  511.4m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 73343 91742 (Trimble GeoXH 6000)

Bwlch Height:  490.8m (LIDAR)

Bwlch Grid Reference:  SN 73790 91963(LIDAR)

Drop:  20.6m (Trimble GeoXH 6000 summit and LIDAR bwlch) (500m Sub-Twmpau addition)

Dominance:  4.02% (Trimble GeoXH 6000 summit and LIDAR bwlch)  

 

 

Esgair Fraith  

Summit Height:  497.2m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 73893 91825 (Trimble GeoXH 6000)

Bwlch Height:  477m (spot height)

Bwlch Grid Reference:  SN 73776 91929 (spot height)

Drop:  20.2m (Trimble GeoXH 6000 summit and spot height bwlch)

Dominance:  4.06% (Trimble GeoXH 6000 summit and spot height bwlch)

 

 

Bryn Mawr  

Summit Height:  487.7m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 72354 90624 (Trimble GeoXH 6000)

Bwlch Height:  414.0m (LIDAR)

Bwlch Grid Reference:  SN 72436 90975 (LIDAR)

Drop:  73.7m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  15.11% (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

 

For further details please consult the Trimble Survey Spreadsheet