Showing posts with label Clo Cadno. Show all posts
Showing posts with label Clo Cadno. Show all posts

Sunday, 29 October 2023

Mapping Mountains – Significant Height Revisions – Welsh Highlands – Uchafion Cymru


Clo Cadno (SO 118 162) 

There has been a Significant Height Revision to a hill that is listed in the Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Aled Williams. 

Clo Cadno (SO 118 162)

The criteria for the list that this height revision applies to are:

Welsh Highlands – Uchafion Cymru Welsh hills at or above 500m in height with 15m minimum drop, with an accompanying sub list entitled the Welsh Highland Subs, the criteria for which is all Welsh hills at or above 500m in height with 10m or more and below 15m of drop.  This list is authored by Myrddyn Phillips and Aled Williams with the Introduction to the list published on Mapping Mountains in November 2015 and the latest update relating to the list published on Mapping Mountains in January 2023.

Welsh Highlands - Uchafion Cymru by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Clo Cadno and it is adjoined to the Cefn yr Ystrad group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and is positioned with minor roads to its north-west and south-west and the B4560 road to its east, and has the village of Llangynidr towards the north-east and the small community of Trefil towards the south. 

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

When the list that later became known as the Welsh Highlands – Uchafion Cymru was first compiled, this hill was not included as the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map have an uppermost 520m ring contour with bwlch contouring between 510m – 520m. 

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

The details for this hill were re-examined via mapping on the OS Maps website.  This is the replacement for OS Get-a-map and had contours at 5m intervals which were proving consistently more accurate compared to the 5m contours that sometimes appear on the Ordnance Survey 1:25,000 Explorer map and the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map, and this mapping indicated that this hill had a minimum of 15m of drop. 

Extract from the interactive mapping that was hosted on the OS Maps 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 image of Clo Cadno (SN 118 162)

LIDAR analysis gives the highest ground on this hill as 530.3m positioned at SO 11849 16247, and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 530.3m and this was derived from LIDAR analysis, this is 10.3m higher than the uppermost 520m ring contour that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Cefn yr Ystrad

Name:  Clo Cadno

OS 1:50,000 map:  161

Summit Height (New Height):  530.3m (LIDAR) 

Summit Grid Reference:  SO 11849 16247 (LIDAR)

Bwlch Height:  513.6m (LIDAR)

Bwlch Grid Reference:  SO 12197 15992 (LIDAR)   

Drop:  16.7m (LIDAR) 

 

Myrddyn Phillips and Aled Williams (October 2023)

 

 

 

  

Thursday, 5 October 2023

Mapping Mountains – Trimble Surveys – Cefn yr Ystrad


02.09.23  Clo Cadno (SO 118 162) 

Clo Cadno (SO 118 162)

Clo Cadno is an attractive looking hill with a line of small crags encircling its upper western fringe.  Looking from its opposing ridge to the north-west it forms one of three hills, with the other two further to its north-east.  These can easily be combined and included with an ascent of their higher neighbour; Mynydd Llangynidr (SO 123 151).  The land hereabouts is open and consists of moorland, therefore not a place to linger when cloud is upon the hills.

My priority for the day was Clo Cadno, this hill is one of five remaining for a completion of the Welsh Highlands – Uchafion Cymru list.  These are the Welsh hills at and over 500m in height that have 15m minimum drop.  The current total is 630, it was more but LIDAR has deleted a number over recent times.

I was out with Aled, who I met in Caersŵs before driving further south to the heads of the valley’s road and onward heading north on a minor road through what is reputedly Wales’ highest village; Trefil.  Approaching the hill from this direction gives an easy ascent from what is now regarded a private quarry road, but was once classified as a B road.  This road is now rough in its upper section and eventually leads to the quarry positioned just below the summit of Cefn yr Ystrad (SO 086 137).  The last time I used this quarry road was in August 2015 when along with Mark Trengove we got locked in, not realising that the barrier across the road just above the last house in Trefil was locked later in the afternoon.  This was on a weekday and necessitated getting a key from the quarry to let us out.  Today was a Saturday and I was unsure whether the barrier would be unlocked during the day.  Driving up the road past the houses of Trefil we approached and there the barrier was; firmly locked across the road.  It had taken two hours to drive here and it seemed our plans would have to be quickly amended.

We stood beside the barrier and debated the best course of action, during this a tractor slowly rumbled up the road and pulled up beside the barrier, the driver obviously had a key and was heading toward fields at the far side of the quarry to work, and after a quick discussion the farmer suggested we follow him up the road and as long as I was back at the barrier within 2½ – 3 hours he would then let me out as he headed back home.  All was saved, although we did have to alter our plans as Aled had suggested surveying Garn Caws (SO 129 167), which as its name implies is crowned by the remains of an ancient cairn and dependent upon what rock is taken as its high point this may alter its current Welsh Highland Sub status. 

Aled's assessment of what was deemed the highest natural rock (marked with a yellow cross) compared to a LIDAR image for Garn Caws (Photo: Aled Williams)

However, a maximum of three hours to visit Clo Cadno, survey its summit, visit the sub positioned at SO 122 167 and continue to Garn Caws and survey its summit before Aled headed over to Mynydd Llangynidr and the Chartist Cave, whilst I headed back to survey the connecting bwlch of Clo Cadno, would in all probability not be sufficient.  Therefore, as my priority was Clo Cadno I was more than happy to just visit and survey its summit.  This would give me an unrushed day and allow a slow plod there and back and a sit in the sun waiting for the farmer to come back down from his fields.

Our plans went beyond this though as after these hills Aled wanted to head toward Cefn yr Ystrad and visit a further four subs, including two impressive rocky lumps left in situ in the quarry and then head down the track leading toward Tor y Foel (SO 114 194), where I would pick him up.

With our plans amended, but the day’s walking and surveying saved, we set off walking at 10.00am on a rough track which was once a part of the classified B road.  This soon headed steeply downhill, whilst our continued route followed a good green track which headed toward Clo Cadno. 

A convenient place to park

It was grey with an oppressive stillness in the air as we ascended.  The forecast gave for warming conditions after the morning murk was burnt off.  The cloud was only just above the tops we headed for, with more under murk to our east. 

Heading off on the path toward the summit of Clo Cadno

From this direction it was only a short walk to the summit of Clo Cadno, but still very enjoyable as we continued up the green track passing one or two wet, boggy patches of land.  Just before the crags we left the main path and were soon standing on the westerly upper part of the hill, just a few minutes’ walk to our east was its nondescript high point.  This consists of low heather and moor grass.  Once we had checked the LIDAR co-ordinates for the summit position which Aled had produced during the updating of the Welsh Highland list with new Welsh LIDAR, I soon had the Trimble positioned on top of my rucksack and as I activated it to gather data, Aled headed off to visit the two subs and inspect the summit cairn of Garn Caws. 

Gathering data from the summit area of Clo Cadno

As the Trimble gathered its allotted five minutes of data I stood away from it so as not to interfere with satellite reception and looked behind me and farther to the east as the grey mornings murk slowly descended.  The high ridge of Mynydd Llangynidr was now under the murk and the cairn atop Garn Caws was only just free of the veil of cloud.  I hoped Aled could do what he wanted and not have the prospect of a couple of hours wandering the wild moors of south Wales under a bed of grey cloud. 

The onward route for Aled, with the summit of Garn Caws on the right

Once allotted data were gathered and stored, I closed the equipment down, took a few photos and then packed it away and started back toward its western top.  Once there I avoided the crags and re-joined our inward route, only stopping to take a few photos of mountain ponies, with one or two making cursory approaches before their timidness backed them away. 

A misty scene in the background with the first glimmers of direct sunlight 

As I approached the rough track leading back to my car a tractor swung on to it from the quarry road.  As it got nearer I flagged it down.  Its driver; Kevin Morris was more than happy to talk about the hills, and as I pointed to one he would give me the name he knew it by.  To my knowledge two of the names he gave have never appeared on an Ordnance Survey map. 

Mountain Ponies on Clo Cadno

After thanking Kevin for his time I waved him off and continued up the slight rise back toward my car, as I did so I noticed a figure emerging from the green path on to the rough track, it was Aled.  We arrived at the car at about the same time, as the murk had descended he decided to just visit the two subs beyond Clo Cadno and also inspect the cairn on Garn Caws, Mynydd Llangynidr and the Chartist Cave could wait for another day. 

Kevin Morris

I then drove further up the quarry road until it got particularly rough with large watery pot holes looking as if they could swallow my car.  After dropping Aled off I drove back down the quarry road, stopped the car to change and then continued down to wait at the barrier, sitting in the emerging sunshine whilst chatting with the occasional walker.  Soon a man with the farmer’s key turned up, he had passed me as I had driven down the quarry road.  I thanked him as he unlocked the barrier and let me out. 

The higher of the two quarry subs (Photo: Aled Williams)

All that remained was to follow my hand written instructions on how to connect with the Llangynidr road from Trefil, after this it was up the steep road leading south of Tor y Foel and further down a track until this merged in to an earthen path.  Here I stopped, sat on a convenient stone bench whilst enjoying the afternoon sun, reading a book and chatting with all manner of people with runners, dog walkers, cyclists and walkers all heading this way and that.  An hour or so after arriving, a weary looking Aled wandered down the path with stories of impressive rocky quarried subs, with one summit that he only touched and not stood on due to large fissures in the rock. 

The lower of the two quarry subs (Photo: Aled Williams)

On our way back we stopped for a meal, sitting outside the Wheelwright Arms in Erwyd enjoying good pub grub in the afternoon warmth, it proved a good way to end an excellent day.  

 

Survey Result:

 

Clo Cadno                                  

Summit Height:  530.3m (LIDAR) (significant height revision)

Summit Grid Reference:  SO 11849 16247 (LIDAR)

Bwlch Height:  513.6m (LIDAR)

Bwlch Grid Reference:  SO 12197 15992 (LIDAR)

Drop:  16.7m (LIDAR) (Welsh Highland P15 addition)

Dominance:  3.15% (LIDAR)

                                       

 

For further details please consult the Trimble Survey Spreadsheet

 

  

Tuesday, 28 January 2020

Mapping Mountains – Hill Reclassifications – Welsh Highlands – Uchafion Cymru


Clo Cadno (SO 118 162) – Welsh Highland P15 addition

There has been an addition to the listing of the Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Aled Williams.

LIDAR image of Clo Cadno (SO 118 162)

The criteria for the list that this addition applies to are:

The Welsh Highlands – Uchafion Cymru This is the revised draft title for the Welsh 500m P15s list that takes in all hills in Wales at or above 500m in height with 15m minimum drop.  The list is co-authored by Myrddyn Phillips and Aled Williams with the Introduction to the list being published on Mapping Mountains in November 2015 and an update relating to the list appearing on Mapping Mountains on the 19th June 2019.

The name the hill is listed by is Clo Cadno and it is adjoined to the Cymoedd Gwent group of hills, which are situated in the eastern part of South Wales (Region C, Sub-Region C2), and is positioned with minor roads to its north-west and south-west and the B4560 road to its east, and has the village of Llangynidr towards the north-east and the small community of Trefil towards the south.

During the compilation of the original list of Welsh 500m P15s that later became known as Yr Uchafion and latterly as the Welsh Highlands – Uchafion Cymru, this hill was not included in the main P15 list as Ordnance Survey 1:25,000 Explorer maps only give an uppermost 520m ring contour with bwlch contouring between 510m – 520m.

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

The details for this hill were re-examined via mapping on the OS Maps website.  This is the replacement for OS Get-a-map and has contours at 5m intervals which are proving consistently more accurate compared to the 5m contours that sometimes appear on Ordnance Survey 1:25,000 Explorer maps and the online Vector Map Local hosted on the Geograph website.  As OS Maps data suggested that this hill had a minimum of 15m of drop it prompted scrutiny using LIDAR.

Extract from the OS Maps website

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.  

Therefore, the addition of Clo Cadno to Welsh Highland P15 status is due to LIDAR analysis, resulting in a 530.3m summit height and a 513.6m bwlch height, with these values giving this hill 16.7m of drop which is sufficient for it to be classified as a Welsh Highland P15.


The full details for the hill are:

Group:  Cymoedd Gwent

Name:  Clo Cadno

OS 1:50,000 map:  161

Summit Height:  530.3m (LIDAR)

Summit Grid Reference:  SO 11849 16247 (LIDAR)

Bwlch Height:  513.6m (LIDAR)

Bwlch Grid Reference:  SO 12197 15992 (LIDAR)
   
Drop:  16.7m (LIDAR) 


For the additions, deletions and reclassifications to The Welsh Highlands – Uchafion Cymru reported on Mapping Mountains please consult the following Change Registers:










Aled Williams and Myrddyn Phillips (January 2020)