Mapping Mountains – Summit Relocations – 500m Twmpau and Yr Uchafion

Cistfaen (SN 867 775)

There has been confirmation of a Summit Relocation to a hill that is listed in the 500m Twmpau and the Yr Uchafion, with the summit height, bwlch height and their locations, drop and status of the hill being confirmed by a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips on the 28^th March 2019, and the height and position of the previously listed summit confirmed by LIDAR analysis conducted by Aled Williams.

Cistfaen (SN 867 775)

The criteria for the two listings that this summit relocation applies to are:

500m Twmpau – Welsh hills at or above 500m and below 600m in height that have 30m minimum drop, with an accompanying sub category entitled the 500m Sub-Twmpau consisting of all Welsh hills at or above 500m and below 600m in height that have 20m or more and below 30m of drop.  With the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.  The list is authored by Myrddyn Phillips.

Yr Uchafion – Welsh hills at or above 500m in height that have 15m minimum drop.  The list is co-authored by Myrddyn Phillips and Aled Williams, with the Introduction to this list appearing on Mapping Mountains on the 4^th November 2015.

The name of the hill is Cistfaen, and it is adjoined to the Elenydd group of hills, which are situated in the central part of Mid and West Wales (Region B, Sub-Region B2), and is positioned with minor roads to its north and south and has the A44 road further to its north and the A470 road to its east, and has the small community of Llangurig and the town of Llanidloes towards the north-east.

When the listing that would later be referred to as Yr Uchafion was first compiled this hill was listed with a summit position placed at SN 86474 77145 based on the 535m spot height that appears on the Ordnance Survey 1:25,000 Explorer map.  This position is in a conifer plantation with the Ordnance Survey 1:50,000 Landranger map also giving a 535m spot height to an ancient cairn that is positioned just outside of the conifer plantation.

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

Extract from the Ordnance Survey 1:50,000 Landranger map

This hill’s summit was subsequently relocated to SN 86788 77502 based on the 536m spot height that appears on the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map.

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

LIDAR only covers the area around the ancient cairn and the 535m map heighted top, and its analysis resulted in the following:

Ancient cairn:  535.0m at SN 86367 77036

535m spot height:  534.9m at SN 86465 77153

The survey with the Trimble GeoXH 6000 at the 536m map heighted summit resulted in the following:

536m spot height:  535.1m at SN 86787 77515

All three results are close in height but as the result produced by the Trimble GeoXH 6000 survey is the highest it is considered the best available evidence for this hill’s summit position and height, and this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies to any listed hill whose summit meets the following criteria; where there are a number of potential summit positions within close proximity and the highest point is not where previously given, 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, or when the summit of the hill is in a different field compared to where previously given, or when the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary that is judged to be a relatively recent man-made construct.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 Explorer map is being prioritised in favour of the 1:50,000 Landranger map for detailing these relocations.

The Trimble GeoXH 6000 gathering data at the summit of Cistfaen

The summit height produced by the Trimble GeoXH 6000 survey is 535.1m and is positioned at SN 86787 77515.  This position is given a 536m spot height on the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map and is approximately 450 metres north-eastward from where the previously listed summit position is situated, and approximately 600 metres north-eastward from the ancient cairn that LIDAR analysis gives as 0.1m higher than the original listed summit position.

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Elenydd

Name:  Cistfaen

OS 1:50,000 map:  135, 136 147

Summit Height:  535.1m (converted to OSGM15)

Summit Grid Reference (new position):  SN 86787 77515

  

Bwlch Height:  512.9m (converted to OSGM15)

Bwlch Grid Reference:  SN 86609 77748

Drop:  22.3m (converted to OSGM15)

For details on the survey of this hill

Myrddyn Phillips and Aled Williams (August 2019)

Mapping Mountains – Trimble Surveys – Elenydd

28.03.19  Cerrig Gwaun y Llan (SN 865 779), Cistfaen (SN 867 775) and Llechwedd y Cloddiau (SN 853 786)

Cerrig Gwaun y Llan (SN 865 779)

In June 2008 I tramped through copious amounts of rough tussock grass approaching from the south to visit the 535m map heighted summit of Cistfaen (SN 864 771) and retraced my steps happy in the knowledge that I’d bagged another 500m P15.  However, summit locations are prone to change and a few years later when the Ordnance Survey Vector Map Local appeared on the Geograph website, the connecting forested summit towards the north-east was given a 536m spot height.  Therefore, I wanted to visit the new summit and if conifers permitted gather Trimble data from its high point.

The weather forecast was set fine for the day with light breeze, blue sky and increasing warmth and I was parked beside a cattle grid at the top of the dead end road at the base of a track leading to the mast atop Llechwedd y Cloddiau and ready to head in to more tussocks by 8.15am.  I’d been this way before in April 2000 and March 2009 and remembered it being rough underfoot with a semblance of a sheep track / narrow path easing passage toward the summit of Cerrig Gwaun y Llan, and I wanted to take advantage of this before the summer months when the rough grass of the Elenydd can hide any semblance of path and make walking particularly difficult.

From where I parked two fences lead down in to the land of tussocks, I followed one and soon made my way to the connecting bwlch of my first hill of the day; Cerrig Gwaun y Llan.  Considering the open nature of this land and the underfoot conditions it was not too difficult to pinpoint the area for this hill’s critical bwlch and the Trimble was soon atop my rucksack gathering its customary five minutes of data.

Gathering data at the critical bwlch of Cerrig Gwaun y Llan

As I stood at the bwlch the only sound that pervaded this land was that of Sky Larks, with soothing incessant song they accompanied me for large stretches of the walk; and proved a welcome backdrop to the wild land of the Elenydd.

A path of sorts headed up from this bwlch and I started on it and soon lost any semblance of its continuing direction and slowly stumbled the remainder of the way on to the broad tussock and heather bound summit ridge of Cerrig Gwaun y Llan and veered right to walk toward its high point on the southern periphery of its summit plateau.

Gentle blue sky shone from above as the Trimble gathered its customary summit data set, as I stood back waiting for the 300 individual datum points to be stored I wondered what the tussock grasslands would be like for the continuation of the walk toward the forest ride that would give access toward the summit of the 536m map heighted hill.

Gathering data at the summit of Cerrig Gwaun y Llan

The walk down to the next connecting bwlch positioned close to the forest ride was broken by a number of large rocks strewn on the moor; a welcome addition for the eye compared to an otherwise bleak but wonderful scene of open moor and quietness.

The forested summit of Cistfaen from the approach to its bwlch

The position of this critical bwlch proved relatively easy to pinpoint and again the Trimble was soon set-up gathering data.  Ahead of me I could see the start of the forest break that led up toward the summit of the hill I wanted to visit and after the Trimble was closed down and packed away I headed toward it.

Gathering data at the critical bwlch of Cistfaen

The forest break proved relatively wide compared to many that I’ve ventured on to over the years and formed a cross roads higher on the summit ridge.  With the bisecting break from the south-west connecting to the lower 535m map heighted summit of Cistfaen, whilst this same forest ride continued to my left toward the higher map heighted summit.

The forest break leading to the summit of Cistfaen

The way up on the left and the summit on the right

Once at the summit I waited an inordinate amount of time for the Trimble to slowly ebb down toward its 0.1m accuracy level before data should be logged and stood silent in shade where nothing stirred with a canopy of blue sky and succulent greens of conifers above.  Every five minutes or so I would dash toward the Trimble to check on its downward progress and walk away knowing that my wait would be a long one, eventually I activated the equipment and waited patiently for it to gather and store data.

Gathering data at the summit of Cistfaen

I now had to retrace my inward route, down through the forest break and across the bwlch, up past the rocks and over the summit of Cerrig Gwaun y Llan and down through the tussocks and heather to its connecting bwlch.  During this my mind wandered and trance like I made steady progress, enjoying the wild land whilst listening to the accompaniment of those ever present Sky Larks.

My original plan was to include a visit and survey of Cefn (SN 851 772) which connects with these hills, but I also wanted to head toward the north-eastern Pumlumon range and re-survey Y Grug (SN 840 934) for Uchaf status, and with a visit to the trig pillar and ancient cairn on Llechwedd y Cloddiau which was positioned above where my car was parked, I decided the survey of Cefn could wait for another day and headed up following the inward fence to the minor road and forest track that leads toward the mast positioned close to the high point of Llechwedd y Cloddiau.

Entering the forest on the track I was met by the gentle scent of pine needles and instantly transported back to a walk through pine forests on Cyprus where piecing blue sky radiated from above.  The forest track soon led me to the mast and a muddied and wet forest break then led onward toward the ancient cairn and trig pillar which constitutes the summit of Llechwedd y Cloddiau.

The trig pillar is positioned in the centre of an ancient cairn which has been re-made to form a wind shelter, although nowadays the forest canopy will give protection from the incoming wind.  The land beside the ancient cairn is now vegetated and on its north-eastern side almost reached the highest rocks of the cairn and as this was solid I decided to place the Trimble here considering it now a part of the hill.

Gathering data at the summit of Llechwedd y Cloddiau

As data were gathered I stood beside the conifers and waited and looked at the moss on trees, the many hued greens and the morning light, it was a quiet scene and one that I appreciated.

All that remained was to retrace my steps back toward the mast and the forest track leading downhill to my awaiting car.  I now wanted to head toward Y Grug for a series of summit and bwlch surveys that I hoped would determine the hill’s status.    

 

Survey Result:

Cerrig Gwaun y Llan

Summit Height:  538.1m (converted to OSGM15)

Summit Grid Reference:  SN 86560 77993

Bwlch Height:  484.5m (converted to OSGM15)

Bwlch Grid Reference:  SN 85778 78270

Drop:  53.6m

Dominance:  9.96%

Cistfaen

Summit Height:  535.1m (converted to OSGM15)

Summit Grid Reference:  SN 86787 77515 (summit relocation retained)

Bwlch Height:  512.9m (converted to OSGM15)

Bwlch Grid Reference:  SN 86609 77748

Drop:  22.3m

Dominance:  4.16%

Llechwedd y Cloddiau

Summit Height:  559.7m (converted to OSGM15)

Summit Grid Reference:  SN 85382 78688

Bwlch Height:  518m (SH)

Bwlch Grid Reference:  SN 85314 79750 (SH)

Drop:  42m

Dominance:  7.45%

For further details please consult the Trimble Survey Spreadsheet