Mapping Mountains – Summit Relocations – Y Pedwarau - The 400m Hills of Wales and Y Trechol – The Dominant Hills of Wales

Rhiw Gwraidd (SO 016 634)

There has been a Summit Relocation that is retrospective to a hill that is listed in the Y Pedwarau - The 400m Hills of Wales and Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill derived from a level and staff summit survey for position conducted by John Barnard, Graham Jackson and Myrddyn Phillips, a Trimble GeoXH 6000 summit survey for height and position conducted by Myrddyn Phillips and LIDAR bwlch analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips.

Rhiw Gwraidd (SO 016 634)

The criteria for the two listings that this retrospective summit relocation affects are:

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are five categories of sub hills; 500m Sub-Pedwarau, 500m Double Sub-Pedwarau, 400m Sub-Pedwarau, 390m Sub-Pedwarau and the 390m Double Sub-Pedwarau.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format. 

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Rhiw Gwraidd and it is adjoined to the Hirddywel group of hills, which are situated in the northern part of South Wales (Region B, Sub-Region B2), and it is positioned with the A44 road to its north and the A470 road to its south-west, and has the town of Llandrindod towards the east south-east.

When the original 400m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, the summit position for this hill was given as SO 009 633, with an accompanying note stating Two tops of same height, other at SO 014 633.  These two tops are given 442m spot heights on the Ordnance Survey 1:25,000 Explorer map, whilst a 440m ring contour further to the east is given a 441m spot height on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map.

Rhiw Gwraidd

442m

SO009633

147

200

Marilyn. Clem/Yeaman. Two tops of same height, other at SO014633.

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

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map

When this hill was line surveyed the summit position was found to be where the 440m ring contour is positioned on the Ordnance Survey 1:25,000 Explorer map, which is just to the east of the easternmost of the two 442m spot heights.  However, its summit height was not surveyed with the Leica equipment and therefore the hill remained with a summit position corresponding to where the 441m spot height appears on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map and yet two 442m spot heights appear further to the west of the high point of this hill.

The line survey that determined the summit position of Rhiw Gwraidd

However, it was not until the survey with the Trimble GeoXH 6000 that an accurate height could be determined.  This survey gives the summit height of this hill as 441.7m positioned at SO 01606 63432, and this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour either on Ordnance Survey maps or interactive mapping, to a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is considered a relatively recent man-made construct, or the de-twinning of a summit, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist.

The Trimble GeoXH 6000 gathering data at the summit of Rhiw Gwraidd with the old position of the summit in the background

Therefore, the height produced by the Trimble GeoXH 6000 survey to the summit of this hill is 441.7m and this is positioned at SO 01606 63432, this position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and is approximately 625 metres and 150m eastward from where the two 442m spot heights appear on the Ordnance Survey 1:25,000 Explorer map.  

The full details for the hill are:

Group:  Hirddywel

Name:  Rhiw Gwraidd

OS 1:50,000 map:  147

Summit Height:  441.7m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference (New Position):  SO 01606 63432 (Trimble GeoXH 6000)

         

Bwlch Height:  229.6m (LIDAR)

Bwlch Grid Reference:  SO 00812 64999 (LIDAR)

Drop:  212.2m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  48.03% (Trimble GeoXH 6000 summit and LIDAR bwlch)

Myrddyn Phillips and Aled Williams (March 2018)

Mapping Mountains – Trimble Surveys – Hirddywel

02.02.18  Llain (SO 031 628), Rhiw Gwraidd (SO 016 634) and Dôl y Fan Hill (SO 015 611)

Dôl y Fan Hill (SO 015 611)

In June 2010 I spent a long time on the summit ridge of Rhiw Gwraidd line surveying it with John Barnard and Graham Jackson; we pinpointed the summit of the hill but did not take a data set with the Leica equipment to establish its height.  Ever since getting the Trimble GeoXH 6000 I’ve wanted to re-visit and gather data from its high point to finally give this hill an accurate summit height.

I set off from the small community of Llanllŷr to the north-west of Llandrindod at just before 9.15am, and with daylight hours now edging past 5.00pm and with a forecast of light breeze and in the main dry conditions, albeit a little chilly, I was in no rush.

A narrow lane headed up toward Fron-serth, I planned on calling, hoping that it was still a farm, it wasn’t, but the man who had moved there with his wife a number of months ago was extremely helpful and walked down the track with me to show where the ladder style was placed and the continuation of the path toward my first summit of the day.

The approach to Llain

Llain is given 19m of drop on Ordnance Survey maps with a 361m summit and 342m bwlch height, therefore it was close to being a Sub-Trichant, this was the only excuse I needed to survey it, this and that by doing so it would form a part of a good circular walk taking in the higher summits of Rhiw Gwraidd and Dôl y Fan Hill.

The view west from the summit of Llain

Although these hills are in the main now grazing pasture, there is a peaceful solitude to wandering such places at this time of year, seldom do you encounter any one, and the land seems to merge, almost sleep, and yet still be alive, it is a sensation that I’ve experienced on many an occasion and yet it still fills me with pleasing and an inner contented happiness.

I took two data sets from the summit area of Llain, with the first my preferred high point; both were good little summits with expansive views.  Whilst the Trimble gathered its allotted five minutes of data from each point I studied the map for which fence to follow down toward this hill’s connecting bwlch and then on to the higher summit of Rhiw Gwraidd.

The first and higher data set taken at the summit of Llain

The second and lower data set taken on Llain

The bwlch proved to be beside a drainage ditch with a small earthen embankment no doubt put in place when the ditch was excavated, I set the Trimble up where I judged the critical bwlch to lie and waited in the morning’s sunshine as it collected another data set.

Gathering data at the bwlch of Llain

Leaving the bwlch I watched two Red Kites majestically circle and glide as their red golden colour flashed against catching sunlight, it was good to be out on the hill even if the fields today were sodden and particularly mud splattered in places.

Beyond the bwlch a footpath led up steepening fields to a number of foot styles and gates giving access toward the track that heads to the large mast perched on one of the number of bumps atop Rhiw Gwraidd.  As I crested the ridge a chilled slight breeze blew and ominous shower clouds had sprung up in adjoining valley’s, their slate grey contrasting against the illuminated light blues and white clouds that otherwise heralded a good dry day.

It wasn’t far beyond the large mast to the high point which is marked by a small embedded rock about one metre from a small cairn.  Before setting the Trimble up aligned to the highest part of the small rock I looked at it and memories of the line survey flooded back, we spent a number of hours on this ridge having a good time and producing an excellent set of results from the line survey, I still feel sad when I think of these times as we operated extremely well as a team both on and off the hill, but life moves on and sometimes events dictate that such times can unfortunately no longer take place.

As the Trimble gathered data the sky menaced from above with shower clouds pushing westward, these glistened on adjacent hillsides covering them wet; I stood and waited for the deluge but thankfully only a few spots lingered my way.

Gathering data at the summit of Rhiw Gwraidd

Packing the Trimble away is always a good moment as it means another data set to process and another accurate result obtained, it also means progress toward the next planned hill and for me this was through a gate and down steeply on ever increasing wet and muddy grass toward the muddied yard of Upper Cilgee.  I stopped and chatted briefly with the farmer’s son and a number of contractors’ before moving on up the lane, by now raindrops were falling pinpointing little echoed waves in brown puddles, my back was to the few drops that fell and it was only these blemishes in near puddles that showed me that the intensity of rain was greater than I imagined.  Leaving the lane for a track hail then started to fall, this only lasted a few minutes and was surprisingly welcome, it brought a different feel to the air, one that chilled, but again it was only fleeting and slowly the blue cascaded down again after the sun appeared.

Dôl y Fan Hill (SO 015 611)

My next survey was the bwlch for Dôl y Fan Hill, this proved to be hard to judge and was somewhere in a large green grazing field, when I arrived there I wandered back and forth and kept trying to follow the undulations toward where the critical bwlch was placed.  I eventually decided on my spot and gathered a five minutes data set, during which a huge shower threatened from the west as it rolled down the valley engulfing the near hills and turning everything wet.  Only a few drops sped my way, I was literally just on the edge of the grey mass of rain and certainly didn’t want to walk toward it, the last I saw of it was as it wandered southward toward Mynydd Epynt throwing out rain drops resembling silvered cascades.

Hail showers massing

Gathering data at the bwlch of Dôl y Fan Hill

Only one survey remained and that was the summit of Dôl y Fan Hill, I used gated fields to gain height to its north-eastward ridge, this proved a delight with ever expansive views and dramatic colour back over Rhiw Gwraidd as another large shower brimmed.

Rhiw Gwraidd with more sleet showers massing

The trig pillar marked the summit and I set the Trimble up aligned with a rock which sat squat beside it.  Whilst gathering data the light was sublime with deep greys and blues above and illuminated colour below, I happily waited for ten minutes of data to be gathered and then stored and just stood and looked and soaked in the view.

The trig pillar at the summit of Dôl y Fan Hill

Colour bounced across the hill, this often happens when low sun and deep grey sky are combined; the colour intensity is often vivid giving an unreal quality to an otherwise pastoral scene.  Such times are to be savoured, the hills give many such moments, but still, one never knows when the next will occur. 

The view northward from the summit of Dôl y Fan Hill

Once the ten minutes were up I pressed ‘Done’ and took a number of photographs before closing the Trimble down and packing it away, all that remained was to follow the north-easterly ridge down to where a track gave access to a field and the continuation of the track contoured around gaining height occasionally leading to the top of a minor lane that took me back to Llanllŷr. 

Gathering data at the summit of Dôl y Fan Hill

Survey Result:

Llain (significant name change)

Summit Height:  360.6m (converted to OSGM15)

Summit Grid Reference:  SO 03132 62802

 

Bwlch Height:  341.3m (converted to OSGM15)

Bwlch Grid Reference:  SO 02794 62943 

Drop:  19.3m 

Dominance:  5.35% 

Rhiw Gwraidd

Summit Height:  441.7m (converted to OSGM15) (Trimble GeoXH 6000)

Summit Grid Reference:  SO 01606 63432 (Trimble GeoXH 6000) (summit relocation)

Bwlch Height:  229.6m (LIDAR)

Bwlch Grid Reference:  SO 00812 64999 (LIDAR)

Drop:  212.2m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  48.03% (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dôl y Fan Hill

Summit Height:  379.9m (converted to OSGM15)

Summit Grid Reference:  SO 01536 61170

Bwlch Height:  309.2m (converted to OSGM15)

Bwlch Grid Reference:  SO 02083 61853 

Drop:  70.7m

Dominance:  18.62%

For further details please consult the Trimble Survey Spreadsheet