Mapping Mountains – Trimble Surveys – Fforest Glud

11.01.14  Old Radnor Hill (SO 251 588)

Old Radnor Hill (SO 251 588)

Old Radnor Hill (SO 251 588) is currently listed as a Subhump with a 317m summit (SO 25122 58775) and 222m bwlch (SO 258 591), giving a drop of 95m.  Until recent times the hill was listed as a Hump with a 327m summit (SO 252 588) and a drop of 110m, giving a bwlch height of 217m.  The reason for the dramatic decrease in height is the Gore Quarry as the old high point is no more and the whole inner section of the hill has been dug out leaving a gaping hole full of quarry workings.

What is left of the hill is positioned in the quiet countryside of Radnorshire, between the villages of Walton and Old Radnor.  As the old summit no longer exists I wanted to survey the remaining high point and establish an accurate height for it, and also investigate the area of the bwlch and see if I could pinpoint where the critical bwlch is and survey it for absolute height.

I approached the hill with intention of visiting the summit first, but driving to the Gore Quarry entrance to familiarise myself with the layout of the bwlch before finding suitable parking for the ascent.  My first surprise was the public road through the quarry is now closed to the public and only accessible to quarry personnel and emergency vehicles.  I quickly turned around and headed back toward Walton and the narrow lane to Old Radnor.

Parking can be found near houses just north of Yatt Farm; from here I headed up on a footpath through a wood and stopped to talk to a woman and her son, who were on their way down.  The young boy kindly told me the way to the top and the woman explained about the quarry and the southerly narrow road now being closed to the public.

Exiting the wood the footpath continued around the southerly slopes of the hill, but as the young boy had said; a bulldozed earthen track bisects it and heads up to the remaining high point.  Within a few minutes the top is reached with a barbed wire fence halting progress to the quarry edge, here a signpost proclaims ‘DANGER this site is not a play area STAY OUT caring for your safety’.  I’m afraid I didn’t stay out and stepped over the fence as others had no doubt done so before me, as the wire fence was now sagging somewhat and gave relatively easy access to the lip of the quarry and the remaining high point of Old Radnor Hill.

The welcoming sign at the remaining high point of  Old Radnor Hill.

Toward the north, the left as one stands on the edge of the drop, is another high point.  I descended a metre or so and used the top of one of the wooden fence posts to align my tiny spirit level with the near high point and the more northerly one, the summit by the sign proved the higher.

During this process I kept looking down in to and across the quarry for any activity, as it was a Saturday it seemed no one was working.  I then dug below the grass to the earth and laid the Trimble on the high point and waited for it to reach its required 0.1m of accuracy before activating it to gather data.  I then retreated to the safer side of the fence and admired the view.  To the south-west is the Dolyhir Quarry obliterating another hill.  However, quarries do not predominate and the hills were on grand display in the afternoon’s sunshine.

The Trimble GeoXH 6000 on the current high point of Old Radnor Hill.

After 11 minutes I switched the Trimble off and retraced my inward route back to the car and drove toward the Gore Quarry entrance on the north-east side of the hill.  The eastern side of the hill has a road cutting through it which transports the A44 southward towards Kington.  The quarry is entered from a small slip road that has access from north and south.  I parked next to the Quarry entrance and started investigating the land beside the upper part of the slip road.  The first surprise was an island of seemingly abandoned and hedged off land between the A44 and the slip road that is higher than the quarry entrance where I’d parked my car.  This is part of the ‘natural’ land as it made its way downward toward the bwlch on the hill to hill traverse.  Examining maps beforehand had pinpointed where the critical bwlch may lie if indeed it was based centrally on both hill to hill and valley to valley traverses.  This is beside a meeting of fences next to the quarry and a large building.  I quickly looked for this spot but decided to wander down to the road cutting and investigate that first.

Thankfully there is plenty of space either side of this road to potter about safely without being squished to smithereens. I found what I thought to be the high point of the road and dug to the earth below the thick grass and set the Trimble gathering data as cars whizzed past.  During data gathering I clambered up the cutting’s incline and sat in the afternoon’s sun feeling content.  Six minutes of data collected I headed back to the slip road and the proper investigation started.

The Trimble gathering data at the high point of the road cutting.

Although I didn’t venture in to the quarry I did look around it from its perimeter, it is extensive with roads, buildings and workings and no sign of any ‘natural’ ground in evidence.  To an extent that last sentence is subjective, as what is ‘natural’ in such an environment?  No gaping holes have been quarried out in the area of the bwlch (except for the road cutting!), but the land has been terra-formed by roads, buildings and their foundations, car parks and the like.  Is any of this natural?  If the ‘natural’ bwlch is under this area it has not been dramatically increased in height by the intrusion of man, but to my eye ‘natural’ ground no longer existed in the area of the quarry.

I then looked at my map (the Ordnance Survey 1:25,000 map is better than the Ordnance Survey enlarged mapping on the Geograph website for pinpointing a centralised point as the more enlarged map has contours disappearing in the area of the quarry workings, whereas the 1:25,000 map has continuous contours).  Walking in a southerly direction I crested the high point of the slip road and visited the field adjacent to the quarry.  This is south of the quarry entrance and just west of the slip road.  It is in the corner of this field where I hoped a centralised ‘natural’ critical bwlch may still exist.  From a southerly direction the land came up to the corner of this field, but to the eye it seemed to continue in a slight rise in to the area of the quarry.  Part of the land beyond the field has a large chapel on it which is adjacent to the slip road.

I placed the Trimble and gathered data in two different spots in this field, one near the corner and one nearer the slip road; the latter seemed the better position on the hill to hill traverse.  Both positions were close to the fence and had trees overhead.  Ten and twelve minutes of data was collected respectively.  

The Trimble gathering data in the corner of the field.

During the process of data gathering I kept assessing the field and its upward slant toward the quarry, the area next to the fence levels off and could be where the ‘natural’ bwlch position is still clinging on for dear life, but the land seemed to continue in a slight (very slight!) rise beyond the boundary fence to land beside a Chapel.

Trimble in the field.  Is this the position of the 'natural' critical bwlch for Old Radnor Hill?

Same position as above, but different view.  Looking across and down the field.

The clue to where the natural bwlch is positioned may lie in the high point of the slip road, as this high point is on the hill to hill traverse and when found all you have to do is follow it by eye either in to the field or beside the Chapel (if the ‘natural’ bwlch remains) or in to the Chapel building / quarry (if the ‘natural’ bwlch no longer remains).  It followed the latter (only just), implying that the ‘natural’ bwlch no longer exists.  However, since this survey LIDAR contouring is now available and this implies that the natural bwlch is intact and is positioned on grass beside the Chapel.

Survey Result:

Old Radnor Hill

Summit Height:  312.6m (converted to OSGM15) (significant height revision)

Summit Grid Reference:  SO 25135 58770

Bwlch Height (beside road):  215.6m (converted to OSGM15)

Bwlch Grid Reference (beside road):  SO 25946 59114

Bwlch Height (in field):  222.7m (converted to OSGM15)

Bwlch Grid Reference (in field):  SO 25888 59083

Bwlch Height (beside Chapel):  222.8m (LIDAR)

Bwlch Grid Reference (beside Chapel):  SO 25887 59097 (LIDAR)

Drop:  97.1m (beside road) (Subhump status reinstated) 

Drop:  89.9m (in field) (Subhump deletion confirmed)

Drop:  89.9m (beside Chapel) (Trimble summit and LIDAR bwlch) (Subhump deletion recommended)

Dominance:  28.74% (Trimble summit and LIDAR bwlch) 

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