Mapping Mountains – Significant Height Revisions – Y Pedwarau – The 400m Hills of Wales

 

Stonewall Hill (SO 318 696) 

There has been a Significant Height Revision to a hill that is listed in the Y Pedwarau – The 400m Hills of Wales under the classification of National Top status (for details relating to the concept of National Tops see separate post), with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and Aled Williams. 

Stonewall Hill (SO 318 696)

The criteria for the list this height revision 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 Y Pedwarau list are five categories of sub hills, with this hill being included in the 400m Sub-Pedwar category.  The criteria for 400m Sub-Pedwar status being all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  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

The name the hill is listed by is Stonewall Hill and it is adjoined to the Beacon Hill group of hills, which are situated in Mid and West Wales (Region B, Sub-Region B1), and it is positioned with the A4113 road to its north, a minor road to its immediate west and the B4355 road farther to its west, and has the town of Trefyclo (Knighton) towards the north-west.

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

When the original 400m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included as the concept of National Tops had not been devised.  The hill was subsequently analysed using contemporary Ordnance Survey maps and LIDAR for height and drop.  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 Stonewall Hill (SO 318 696)

LIDAR analysis confirms this hill as over 400m in height, and as the summit has now been surveyed with the Trimble GeoXH 6000, it is this result that is being prioritised for listing purposes 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 summit 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. 

The Trimble GeoXH 6000 gathering data at the summit of Stonewall Hill

Therefore, this hill’s new listed summit height is 400.1m and this was derived from a Trimble GeoXH 6000 survey, this is 5.1m higher than the uppermost 395m ring contour taking in the summit of this hill on contemporary Ordnance Survey maps, although an erroneous 400m ring contour is shown toward the west. 

 

The full details for the hill are:

Group:  Beacon Hill 

Name:  Stonewall Hill

OS 1:50,000 map:  137, 148

Summit Height (New Height):  400.1m (converted to OSGM15)

Summit Grid Reference:  SO 31823 69655

Bwlch Height:  376.4m (converted to OSGM15)

Bwlch Grid Reference:  SO 31273 70279

Drop:  23.8m

 

Myrddyn Phillips and Aled Williams (October 2021)

 

 

Mapping Mountains – Hill Reclassifications – Y Pedwarau – The 400m Hills of Wales

 

Stonewall Hill (SO 318 696) – 400m Sub-Pedwar addition

There has been an addition to the listing of the Y Pedwarau – The 400m Hills of Wales under the classification of National Top status (for details relating to the concept of National Tops see separate post), with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and Aled Williams. 

Stonewall Hill (SO 318 696)

The criteria for the list that this addition applies to 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 Y Pedwarau list are five categories of sub hills, with this hill being added to the 400m Sub-Pedwar category.  The criteria for 400m Sub-Pedwar status being all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  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

The name the hill is listed by is Stonewall Hill and it is adjoined to the Beacon Hill group of hills, which are situated in Mid and West Wales (Region B, Sub-Region B1), and it is positioned with the A4113 road to its north, a minor road to its immediate west and the B4355 road farther to its west, and has the town of Trefyclo (Knighton) towards the north-west.

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

Extract from the Ordnance Survey series of Six-Inch maps showing the course of the border

Extract from the Magic Maps website showing the course of the border

When the 1^st edition of the Y Pedwarau was published by Europeaklist in May 2013, this hill was not included as the concept of National Tops had not been devised.  The hill was subsequently analysed using contemporary Ordnance Survey maps and LIDAR for height and drop.  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 Stonewall Hill (SO 318 696)

LIDAR analysis confirms this hill as over 400m in height, and as the summit has now been surveyed with the Trimble GeoXH 6000, it is this result that is being prioritised for listing purposes. 

Gathering data at the summit of Stonewall Hill

Therefore, the confirmation of the addition of this hill to 400m Sub-Pedwar status under the National Top classification is due to LIDAR analysis and a subsequent Trimble GeoXH 6000 survey, resulting in a 400.1m summit height and a 376.4m bwlch height, with these values giving this hill 23.8m of drop which is sufficient for it to be classified as a 400m Sub-Pedwar. 

 

The full details for the hill are:

Group:  Beacon Hill 

Name:  Stonewall Hill

OS 1:50,000 map:  137, 148

Summit Height:  400.1m (converted to OSGM15)

Summit Grid Reference:  SO 31823 69655

Bwlch Height:  376.4m (converted to OSGM15)

Bwlch Grid Reference:  SO 31273 70279

Drop:  23.8m

 

For the additions, reclassifications and deletions to Y Pedwarau – The 400m Hills of Wales reported on Mapping Mountains since the May 2013 publication of the list by Europeaklist please consult the following Change Registers:

 

Y Pedwarau

 

Y Pedwarau – 400m Sub-Pedwarau

 

Y Pedwarau – 390m Sub-Pedwarau

 

Y Pedwarau – 390m Double Sub-Pedwarau

 

Aled Williams and Myrddyn Phillips (October 2021)

 

 

 

 

Mapping Mountains – Trimble Surveys – Beacon Hill

 

28.08.21  Stonewall Hill (SO 318 696) 

Stonewall Hill (SO 318 696)

Stonewall Hill had previously been surveyed on the 17^th July, just over five weeks later and Aled and I were again back on its summit.  We parked on the high narrow lane that skirts the border with England and headed back to its high point for more summit data.  The reason for doing so was that the higher of two previous summit surveys came to 399.97m, just 3cm below 400m. 

Stonewall Hill is one of two hills that are listed under the newly created status of National Top, each are now included in the Y Pedwarau – The 400m Hills of Wales list, the other being Hergest Ridge (SO 246 557).  The concept of National Tops is explained in a separate post and for the lists co-authored with Aled Williams, this status affects just these two hills. 

The summit of Stonewall Hill consists of a mound; its highest part has slight undulations but only comprises a small area.  We debated whether three or five further surveys were sufficient.  Four are documented and combined with the two previous surveys give six in all. 

Once on the summit Aled prodded around and we quickly decided the approximate position for each survey.  We then spent about 50 minutes hunkered below the survey equipment as it gathered one data set closely followed by another. 

Gathering data at the summit of Stonewall Hill

We debated whether this was the most unusual Trimble survey to have taken place, as the hill is now a National Top, which is a new concept, this was a re-survey, it is positioned within a couple of minutes’ walk from a road and the summit is on top of a mound of unknown origin. 

However, it is a good little top and has extensive views out toward the Clee Hills.  Once all data sets were gathered and stored we headed back to the car.  The processed result will tell us whether this hill makes it to the 400m height barrier! 

 

Survey Result: 

 

Stonewall Hill

Summit Height:  400.1m (converted to OSGM15) (400m Sub-Pedwar addition under National Top status) (significant height revision)

Summit Grid Reference:  SO 31823 69655  

Bwlch Height:  376.4m (converted to OSGM15, from previous Trimble GeoXH 6000 survey)

Bwlch Grid Reference:  SO 31273 70279 (from previous Trimble GeoXH 6000 survey)

Drop:  23.8m

Dominance:  5.95%

 

 

For details on the 1^st summit survey of Stonewall Hill

 

For further details please consult the Trimble Survey Spreadsheet

 

 

 

Mapping Mountains – Trimble Surveys – Beacon Hill

17.07.21  Stonewall Hill (SO 318 696) 

Stonewall Hill (SO 318 696)

Stonewall Hill was the second National Top that Aled and I planned on visiting and surveying during the day.  We had just visited the first; the Welsh summit of Hergest Ridge (SO 246 557) and duly surveyed it.  

The border hereabouts follows the course of a narrow lane with the summit of The Warren (SO 318 685) which is classified as an English Sub-Four, just to its east, whilst the summit of Stonewall Hill is just in Wales.  The concept of National Tops is explained in a separate post and for the lists co-authored with Aled Williams, this status affects just these two hills. 

If wanting, the narrow road that follows the border before veering eastward gives opportunity for a quick ascent of The Warren and the National Top of Stonewall Hill.  I’d previously visited The Warren so waited beside my car as Aled walked to its high point.  Once Aled had returned I drove the short distance on the continuation of the narrow road and pulled in beside the gate that gives access to a public footpath leading through the mixed wood to the summit of Stonewall Hill. 

By now the heat was becoming increasingly uncomfortable and especially so if doing any form of excursive.  As I got my camera, map and rucksack out of the car and then locked it, I could hear a good deal of bashing going on, this came from the undergrowth on the opposing side of the gate; Aled was submerged in the public footpath that doesn’t seem to be used very often as summer growth had formed a jungle around its narrow confines. 

By the time I joined Aled a path of sorts was emerging through the undergrowth aided by a branch that was being used to swat the long grass, nettles and any other form of greenery that had swamped the path.  I was glad it was Aled doing this and not me as all I wanted was the easiest route and as little uphill as possible, even following in Aled’s footsteps was tiring. 

On the path through the wood

Eventually the undergrowth gave way to easier conditions through the mixed wood and led us to a mound which had a stunted tree near its high point; leading to it was a sea of green fern.  This was the summit of the newly acclaimed Nation Top of Stonewall Hill.  Considering the conditions we had walked through, the summit was relatively open which gave good opportunity for the Trimble to log on to orbiting satellites. 

Approaching the summit of Stonewall Hill

Once at the top Aled assessed the lay of land and we decided to take two data sets, about one metre apart.  During data collection Aled sat below the equipment to its immediate south and I scribbled all necessary detail in my surveying notebook. 

Gathering data at the summit of Stonewall Hill

Adjacent to the summit of Stonewall Hill was a ploughed field, between the summit and the field’s easy underfoot conditions was a barb wired fence, and beyond the field the narrow road.  This looked an easier route back when compared to retracing our inward trek, and once the Trimble had gathered and stored its second data set I closed it down, packed it away and in to the field we went.  From here it was only a short walk back to the car. 

The two National Tops had now been visited and surveyed and their newly acquired classifications confirmed.  It had been a good morning on the hill, but one hill still remained to visit; Farrington Bank (SO 305 699).

 

Survey Result: 

 

Stonewall Hill

Summit Height:  400.1m (converted to OSGM15, from subsequent Trimble GeoXH 6000 survey) (400m Sub-Pedwar addition under National Top status) (significant height revision)

Summit Grid Reference:  SO 31823 69655 (from subsequent Trimble GeoXH 6000 survey)   

Bwlch Height:  376.4m (converted to OSGM15, from previous Trimble GeoXH 6000 survey)

Bwlch Grid Reference:  SO 31273 70279 (from previous Trimble GeoXH 6000 survey)

Drop:  23.8m

Dominance:  5.95%

For details on the 2nd survey of Stonewall Hill 

 

For further details please consult the Trimble Survey Spreadsheet