Showing posts with label Allt Goch. Show all posts
Showing posts with label Allt Goch. Show all posts

Friday, 18 November 2022

Mapping Mountains – Hill Reclassifications – Y Trichant – The 300m Hills of Wales


Allt Goch (SN 947 972) – Sub-Trichant addition

There has been confirmation of an addition to the list of Y Trichant – The 300m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Allt Goch (SN 947 972)

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

Y Trichant – The 300m Hills of Wales – Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant, with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13th May 2017, and the Introduction to the Mapping Mountains publication of the list appearing on the 1st January 2022. 

Y Trichant - The 300m Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Allt Goch, and it is adjoined to the Pumlumon group of hills, which are situated in the northern part of South Wales (Region B, Sub-Region B1), and it is positioned with the A470 road to its north-east and a minor road to its south, and has the village of Carno towards the south-east.

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with 21m of drop, based on the 309m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 288m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

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

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.

Therefore, the confirmation of the addition of this hill to Sub-Trichant status is due to LIDAR analysis, resulting in a 308.4m summit height and a 288.2m bwlch height, with these values giving this hill 20.2m of drop, which is sufficient for it to be classified as a Sub-Trichant. 

 

The full details for the hill are: 

Group:  Pumlumon 

Name:  Allt Goch 

OS 1:50,000 map:  136

Summit Height:  308.4m (LIDAR)                                                           

Summit Grid Reference:  SN 94775 97259 (LIDAR) 

Bwlch Height:  288.2m (LIDAR) 

Bwlch Grid Reference:  SN 94675 97387 (LIDAR) 

Drop:  20.2m (LIDAR) 

 

Myrddyn Phillips (November 2022)

 

 

 

 

 

 

 

  

Saturday, 13 February 2021

Mapping Mountains – Trimble Surveys – Elenydd

 

22.10.20  Allt Goch (SN 671 773) 

LIDAR image of Allt Goch (SN 671 773)

This hill was the third of seven that I planned on visiting during the day, and prior to this I had analysed its numerical details via LIDAR.  LIDAR shows the upper part of the hill to consist of a slender mound running in a north to south direction and the bwlch positioned to the east north-east of the summit on or beside the A4120 road. 

A conveniently placed bridleway marches across this hill from north to south and this gave an easy option for the ascent.  I found parking on the grass verge beside the road a few metres west from where the bridleway started. 

The bridleway consists of a track and as I gained height on it the first flashes of morning light highlighted parts of the surrounding land.  Prior to this the skies had been overcast, and although the higher tops to the east were still bathed in clag, I had spotted a number of the hills I planned on visiting later in the day and their summits were all below the cloud base. 

Autumnal light can be wonderful with it highlighting the colourful display on trees, when their golden yellows and rusted reds are mixed along with browns and oranges giving a myriad of colour.  This is only enhanced when grey sky predominates, as this forms an ideal backdrop for autumnal light.  Although the cloud had started to break up and sunlight gave intermittent colour it wasn’t until later in the day that I was treated this magical display of autumnal light. 

The track soon led to a gate and this gave access to the upper field where the summit of the hill is situated.  Once on the high point I assessed the lay of land for Trimble placement, two points vied for the accolade of summit position, each only a couple of metres from the other.  Having chosen what I judged to be the highest I set the Trimble up to gather data. 

Gathering data at the summit of Allt Goch

During data collection I stood away from the equipment and scribbled all necessary detail in my notebook, including the measurement offset, name of hill, point of survey (summit or bwlch), time the equipment was activated to gather data, number of satellites logged on to, estimated margin of positional uncertainty, feature at summit or bwlch, number of points gathered and the time duration of the survey. 

All of the above passes a minute or two and as the normal allotted time for each survey is five minutes, the time spent at the summit soon passes, and today I also kept an eye on four horses, and although they has spotted me they thankfully kept their distance.  Once five minutes of data were gathered and stored I headed back up to the summit and closed the equipment down, took a few photos and packed it away. 

The Trimble set-up position at the summit of Allt Goch

Before leaving the summit I looked out toward my next hill of the day; Penpegws (SN 702 755).  This was to my south-east and whereas the first three hills of the day were accessed from the convenience of the A4120 road, the remaining four hills all had starting points from narrow lanes, and with each positioned close to a lake it was an area that I was looking forward to investigating. 

 

Survey Result: 

 

Allt Goch  

Summit Height:  238.8m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 67119 77395 (Trimble GeoXH 6000) 

Bwlch Height:  192.1m (LIDAR)

Bwlch Grid Reference:  SN 67881 77648 & SN 67876 77643 (LIDAR)

Drop:  46.7m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  19.56% (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

 

For further details please consult the Trimble Survey Spreadsheet

 

 

 

 

Tuesday, 19 August 2014

Mapping Mountains – Trimble Surveys – Y Berwyn


15.08.14  Sycharth (SJ 205 258), Mynydd y Bryn (SJ 217 268) and Allt Goch (SJ 209 252)


An artist's impression of Sycharth

In the heartland of mid Wales where country lanes lead to quiet farms and green hills predominate, and where the waters of the Cynllaith ebb and flow in to the Afon Tanat are the remains of Sycharth; a solidary Motte and Bailey castle perched above the river now overlooked by mixed forestry that descends south-westward from the summit of Mynydd y Bryn.

Sycharth is one of the two traditional principal courts of Owain Glyndŵr, it is where he was born and it is where, in May 1403 Harry of Monmouth, later to become King Henry V, visited with unfriendly intention, writing to his father King Henry IV on 15th May 1403 that ‘we took our people and went to a place of the said Oweyn, well built, which was his principal mansion called Saghern, where we supposed that we should have found him if he had been willing to have fought in the manner as he said, but upon our arrival we found no one; hence we caused the whole place and many of his other houses of his tenants in the neighbourhood to be burnt and then went directly to his other place of Glyndourdy (Glyndyfrdwy) to seek for him there. We caused a fine lodge in his park to be burned and all the country therabout and we lodged at rest there all that night...’

Glyndŵr’s residence of Sycharth is described in a praise poem by Iolo Goch which was written before the Welsh revolt.  Goch refer’s to the generosity of Glyndŵr as a host and mentions the continental European and Anglo-Norman inspiration for the architecture, describing Sycharth as containing ‘nine plated buildings on the scale of eighteen mansions, fair wooden buildings on top of a green hill’ and ‘a tiled roof on every house with frowning forehead, and a chimney from which the smoke would grow; nine symmetrical, identical halls, and nine wardrobes by each one.’

Today the site is a quiet haven of contemplation of times long gone and opportunity unfulfilled.  The remains of this once proud emblem of a fledgling nation is now no more than a grassed mound with customary earthwork.  However, the site is impressive, partly for its solitude and ambience, but also for its size, as excavations in the early 1960’s revealed the presence of two timber halls on the flat topped mound, one being 43 metres in length.  These excavations also unearthed evidence of the site being burnt, a reminder of the destruction from over 500 years ago.

Approaching Sycharth across the field from the small car park

Part of the moat, see artist's impression above

Sycharth is highly recommended to visit, two interpretive boards giving a brief history of the site with an artist’s impression of what it once looked like and an aerial view of the site as it is nowadays greet the visitor in a recently installed small car park.  In other realms this site may have had a full blown £10 entry fee with a singing and dancing video experience including a 3D venture around the site as it was in the late 1300’s.  Thankfully this has not happened, it remains a site landscaped in beauty, somewhere to visit both for historians and those rebellious at heart.

An aerial view of Sycharth

I’d only visited once before when I took my Father there, unfortunately he was at an age that he could not walk to the site and so remained in the car, having enjoyed the journey there he was happy to wait for me to visit the earthen mound and wander around it for 15 minutes.  Today’s visit was a little different as I wanted to extend the walk and take in two P30’s; Mynydd y Bryn and Allt Goch either side of Sycharth to its east.

From the small car park a track leads to a ladder stile which gains access in to the field where Sycharth is situated.  The earthen mound rises ahead, now surrounded by mature trees with its outer embankment still an impressive sight.  This morning the sun highlighted the colours of the lion’s rampant on the standard of Glyndŵr that had been attached to a number of the surrounding trees, a sign that the site is not forgotten.

The Lion's Rampant - the Standard of  Owain Glyndŵr

The Standard of Glyndŵr bears witness over Sycharth

I spent quite some time wandering around; it was as I remembered it from so many years ago, the flatbed of its top being grassy and having summer thistles springing up.  It wasn’t my intention to measure its absolute height as the ‘hill’ only has about 13 – 14 metres of prominence, but as I was there, I thought ‘why not’.  As the Trimble crept down to its required 0.1m accuracy before data can be logged, I pottered about taking photographs as the mewing pee-oo of a Buzzard added depth to the surroundings.  Once the accuracy had been achieved and data collected I packed the Trimble away and bade my farewells to Sycharth and headed back to the ladder stile which gave access to a forest track.

Gathering data at the high point of Sycharth

The forest track soon bisects with the lower branch heading toward a footpath, whilst the higher branch continued through the forestry, with both meeting higher up the side of the hill.  The hill being; Mynydd y Bryn, one of the few P30’s in this area that I had not previously visited.  Glimpses through the trees gave views of the 523m hill named Gyrn Moelfre on the map, as height was gained the green track emerged out of the forest to give views westward toward the high Berwyn, from this point their eastern wedged ridge being on grand display.

Looking through the trees toward the 523m hill named as Gyrn Moelfre on the map

By now the morning’s sunshine was being quickly overtaken with a build-up of grey pockets of cloud, heralding heavy afternoon showers, I hoped that my walk wouldn’t take too long as with a 3.00pm appointment in the near town of Oswestry I wanted to be down from the hill by 1.30pm and the cloud predicted that if my time on the hill was protracted I may get a wee bit wet.

The high Berwyn in the background

The green track soon swung around the higher northerly ridge of Mynydd y Bryn and soon deposited me at the summit, which has a cairn, small trees and loose rocks.  I picked my spot for Trimble placement and gathered ten minutes of data as the sun disappeared behind the grey cloud.  Away to the north-east the first signs of showers could distinctly be seen as their grey sheen scattered raindrops on the ground below.  There are excellent views from this hill’s summit looking beyond the Stiperstones and the Wrekin to the flatlands of Shropshire, to the west a multitude of hills took in the splendours of Y Berwyn whilst farther away the high Aran rose up and dominated.

The high Aran dominating the view south-westward

The Trimble GeoXH 6000 gathering data at the summit of Mynydd y Bryn

Once the Trimble was packed away I headed down the south-west ridge of the hill and soon started to encounter barbed wire fences, thick fields of ferm, some of which was chest high, an occasional boggy bit and a lot of low overhanging tree branches.  As I stumbled my way over another barbed wire fence I picked up a vehicle track over a field that lead down to a footpath and the connecting bwlch between Mynydd y Bryn and my next and last hill of the day; Allt Goch.

The bwlch consisted of a neatly cropped large field just beyond the farm house of Pen-y-graig-isaf, as I placed the Trimble on the ground a woman approached from the farm; I went over and chatted with her for five minutes, explaining what I was doing.  She didn’t mind, and explained that the field had recently had a marquee erected on it which explained why there was a large square shape with the grass being of lighter colour.

Somewhere on that expanse of green is a Trimble, with Allt Goch looking down on its critical bwlch

Once data were collected I headed up to the first summit of Allt Goch, this is given a 227m spot height on the Ordnance Survey enlarged mapping on the Geograph website just south of a fence that splits the first summit, I found ground to the north of this fence to be the higher on this particular summit.  By now the Trimble was taking an age to achieve the required accuracy, this sometimes happens and can be quite frustrating if on a walk with a friend, when on my own I usually sit and patiently wait, today I had to sit and wait for over 30 minutes and it was only at the fourth attempt and only after I used the improvised Tupperware and draugths board tripod that the required 0.1m accuracy was achieved.

Gathering data at the first option for the summit of Allt Goch.  This is at SJ 21069 25292 and came to 226.221m

The second option for the summit of Allt Goch was just to the south-west and has a 228m spot height adjoined to it on Ordnance Survey maps.  I placed the Trimble on its improvised tripod a few metres from a stone wall and sat and waited.  The spot height on the map appears directly next to this wall, on the western side of which if woodland, the Trimble placement was clear of trees and looked as high as where the spot height appears on the ground. 

Gathering data at the second option for the summit of Allt Goch.  This is at SJ 20912 25241 and came to 226.732m

As I checked the route back to the awaiting car on the map I felt an occasional drop of rain that was blown westward from the greying clouds away to the east.  I’d kept my eye on the weather to the east for the last couple of hours as this was where shower clouds were massing, but as I descended to the lane and headed back toward the car next to Sycharth the weather to the west suddenly started to close in heralding outbursts of heavy afternoon showers.  Thankfully I arrived back at the car in time to change and pack my gear away before the downpours arrived and in time for my 3.00pm appointment in Oswestry.  On the way I drove in to heavy showers, no more than three miles from where I’d been walking the hills, with the road soaked and puddles of water cast on the ground, good timing I thought!


Survey Result:


Sycharth

Summit Height:  146.8m (converted to OSGM15)  

Summit Grid Reference:  SJ 20540 25873

Drop:  12.9m (converted to OSGM15) (from later bwlch survey)

Dominance:  8.82%





Mynydd y Bryn

Summit Height:  334.8m (converted to OSGM15, Trimble GeoXH 6000)  

Summit Grid Reference:  SJ 21715 26858 (Trimble GeoXH 6000)

Bwlch Height:  210.5m (LIDAR)

Bwlch Grid Reference:  SJ 22591 26635 (LIDAR)

Drop:  124.3m (Trimble GeoXH 6000 summit and LIDAR bwlch) 

Dominance:  37.13% (Trimble GeoXH 6000 summit and LIDAR bwlch)



 

Allt Goch

Summit Height:  226.8m (converted to OSGM15) 
 
Summit Grid Reference:  SJ 20912 25241

Bwlch Height:  194.1m (converted to OSGM15)

Bwlch Grid Reference:  SJ 21139 25570

Drop:  32.7m  (200m Twmpau status confirmed)

Dominance:  14.40%





For details on the bwlch survey of Sycharth

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