Mapping Mountains – Significant Name Changes – 200m Twmpau

Llwynderw Hill (SJ 196 036) 

There has been a Significant Name Change to a hill that is listed in the 200m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips. 

LIDAR image of Llwynderw Hill (SH 196 036)

The criteria for the list that this name change applies to are: 

200m Twmpau - Welsh hills at or above 200m and below 300m in height with 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 200m Twmpau by Myrddyn Phillips

The hill is adjoined to the Carnedd Wen group of hills which are situated in the south-eastern part of North Wales (Region A, Sub-Region A4), and it is positioned with minor roads to its north, west and south and the A483 road to its south-east, and has the town of Y Trallwng (Welshpool) towards the north-east. 

When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was listed under the invented and transposed name of Pen y Belan, with an accompanying note stating; Name from surrounding district.

 

Pen y Belan

238m

SJ196036

136

216

Name from surrounding district

During my early hill listing I thought it appropriate to either invent a name for a hill, or use a name that appeared near to the summit of the hill on Ordnance Survey maps of the day.  My preference was to use farm names and put Pen, Bryn or Moel in front of them or as in this instance transpose the name of the district where the hill is situated and add the words Pen y to it.  This is not a practice that I now advocate as with time and inclination place-name data can be improved either by asking local people or by examining historic documents, through this form of research an appropriate name for the hill can usually be found. 

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

When I first visited this hill in June 2011 I called at Mount Farm (SJ 190 040) and met Peter Holloway.  Peter is local to the area and has farmed from Mount Farm all of his life.  I asked about the names of a number of local hills and for this hill he told me that he knows it as Llwynderw Hill. 

Therefore, the name this hill is now listed by in the 200m Twmpau is Llwynderw Hill, and this was derived from local enquiry. 

 

The full details for the hill are:

Group:  Carnedd Wen

Name:  Llwynderw Hill

Previously Listed Name:  Pen y Belan   

OS 1:50,000 map:  136

Summit Height:  237.9m (converted to OSGM15, Trimble GeoXH 6000) 

Summit Grid Reference:  SJ 19600 03662 (Trimble GeoXH 6000) 

Bwlch Height:  159.7m (LIDAR) 

Bwlch Grid Reference:  SJ 18827 03989 (LIDAR) 

Drop:  78.3m (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

Myrddyn Phillips (June 2021)

 

 

  

Mapping Mountains – Summit Relocations – 200m Twmpau

 

Llwynderw Hill (SJ 196 036) 

There has been a Summit Relocation to a hill that is listed in the 200m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips. 

LIDAR image of Llwynderw Hill (SJ 196 036)

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

200m Twmpau – Welsh hills at or above 200m and below 300m in height that have 30m minimum drop, with an accompanying sub category entitled the 200m Sub-Twmpau consisting of all Welsh hills at or above 200m and below 300m 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 200m Twmpau by Myrddyn Phillips

The name the hill is listed by is Llwynderw Hill and this was derived from local enquiry, and it is adjoined to the Carnedd Wen group of hills which are situated in the south-eastern part of North Wales (Region A, Sub-Region A4), and it is positioned with minor roads to its north, west and south and the A483 road to its south-east, and has the town of Y Trallwng (Welshpool) towards the north-east. 

When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was included in the main P30 list, and listed with a 238m summit height, based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer 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. 

LIDAR analysis shows the ground on a raised field boundary to be the highest on the hill, however as this is deemed a relatively recent man-made construct such ground is discounted from the height of a hill in the listings I author.  LIDAR analysis also shows the position of the highest remaining natural ground and this has now been surveyed with the Trimble GeoXH 6000 and it is this result that is being prioritised for this hill. 

LIDAR summit image of Llwynderw Hill

The summit height and position produced by the Trimble GeoXH 6000 survey is 237.9m at SJ 19600 03662, and this position in relation to the raised field boundary shown by LIDAR analysis comes within the parameters of the Summit Relocations used within this page heading, these parameters are: 

The term Summit Relocations applies when the hill’s high point is found to be positioned; in a different field, to a different feature such as in a conifer plantation, placed within a different map contour, to a different point where a number of potential summit positions are within close proximity, or when natural ground or 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, 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. 

The Trimble GeoXH 6000 gathering data at the natural summit of Llwynderw Hill

Therefore, the new listed summit height for this hill is 237.9m and is positioned at SJ 19600 03662, this position is not given a spot height on contemporary Ordnance Survey maps and is in a different field to where the 238m spot height is positioned on the Ordnance Survey 1:25,000 Explorer map and is approximately seven metres east north-eastward from where LIDAR gives the high point of the raised field boundary. 

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Carnedd Wen

Name:  Llwynderw Hill

OS 1:50,000 map:  136

Summit Height:  237.9m (converted to OSGM15, Trimble GeoXH 6000) 

Summit Grid Reference (New Position):  SJ 19600 03662 (Trimble GeoXH 6000) 

Bwlch Height:  159.7m (LIDAR) 

Bwlch Grid Reference:  SJ 18827 03989 (LIDAR) 

Drop:  78.3m (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

Myrddyn Phillips (June 2021)

 

 

 

 

 

Mapping Mountains – Hill Reclassifications – Y Trechol – The Dominant Hills of Wales

Llwynderw Hill (SJ 196 036) – Lesser Dominant deletion

There has been a deletion to the listing of Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill derived from LIDAR analysis and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips. 

LIDAR image of Llwynderw Hill (SJ 196 036)

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

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format. 

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Llwynderw Hill and this was derived from local enquiry, and it is adjoined to the Carnedd Wen group of hills which are situated in the south-eastern part of North Wales (Region A, Sub-Region A4), and it is positioned with minor roads to its north, west and south and the A483 road to its south-east, and has the town of Y Trallwng (Welshpool) towards the north-east. 

After the original 200m height band of Welsh P30 hills published on Geoff Crowder’s v-g.me website were standardised and interpolated heights also included, this hill was listed with an estimated c 80m of drop and 33.61% dominance, based on the 238m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 158m bwlch height, based on interpolation of 5m contouring between 155m – 160m that appears on the Ordnance Survey 1:25,000 Explorer 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. 

LIDAR analysis confirmed the natural summit position of this hill and decreased its dominance to 33.87%, and as the summit of this hill has now been surveyed with the Trimble GeoXH 6000 it is this result that is being prioritised in preference to the LIDAR height and position, resulting in a summit height of 237.9m positioned at SJ 19600 03662. 

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

Therefore, the deletion of this hill from Lesser Dominant status is due to LIDAR bwlch analysis and a Trimble GeoXH 6000 summit survey, resulting in a 237.9m summit height and a 159.7m bwlch height, with these values giving this hill 78.3m of drop and 32.89% dominance, which is insufficient for it to be classified as a Lesser Dominant hill. 

 

The full details for the hill are:

Group:  Carnedd Wen

Name:  Llwynderw Hill 

OS 1:50,000 map:  136

Summit Grid Reference:  SJ 19600 03662 (Trimble GeoXH 6000)

Summit Height:  237.9m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SJ 18827 03989 (LIDAR)

Drop Summit to Bwlch:  78.3m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Drop Bwlch to ODN:  159.7m (LIDAR)

Dominance:  32.89% (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

Myrddyn Phillips (June 2021)

 

 

 

 

 

 

 

  

Mapping Mountains – Trimble Surveys – Carnedd Wen

 

25.02.21  Llwynderw Hill (SJ 196 036)

LIDAR image of Llwynderw Hill (SJ 196 036)

I’d visited this hill once before in June 2011 and on that occasion the circular walk from my home taking in its summit formed one of a number of preparation walks for the Fisherfield surveys conducted for The Munro Society.  Then I did not have a Trimble, now I do and the hill was within easy striking distance from my home for a socially distanced lock down walk. 

Prior to this re-visit I had examined the details for the hill via LIDAR and noted an accurate height and position for both its summit and bwlch, with the natural summit being prioritised over the higher field boundary. 

Llwynderw Hill is positioned overlooking the Severn Valley and can be easily accessed from the convenience of the Montgomeryshire Canal.  My walking companions for the day were Linda and Nic and we met beside the wharf next to Morrisons car park. 

Linda, Tommy the dog and Nic on the canal towpath

The ducks were shining their bright coloured feathers in the morning sunshine as we leisurely made our way out of town following the canal towpath.  This was a change from what has become the norm of using the Cefnyspin and Frochas Lanes to access Y Golfa and its adjacent hills.  And however beautiful and welcome that route had become it was good to have a change of scene. 

Beyond Belan Lock the opposite side of the canal was awash in dazzling Snowdrops, they shined back at us all whitened standing upright in the late February sunshine as the first warmth of spring continued to take hold. 

Admiring the Snowdrops

We left the canal towpath after almost three miles and headed west up a steepening narrow lane which although highlighted yellow on contemporary Ordnance Survey 1:25,000 Explorer maps, is not recommended to drive up as one steep section is particularly daunting where the paved section has crumbled leaving a ramp.  Thankfully, today we were walking and not attempting to drive. 

Nearing the high point of the narrow lane we accessed a field next to a gate and continued up toward the high point.  The girls found a sheltered spot to indulge in lunch, whilst I sauntered over to the summit zeroing in on the ten figure grid reference produced from LIDAR analysis for the natural high point.  I soon had the Trimble set-up gathering data and re-joined the girls whilst it quietly beeped away collecting its individual datum points. 

Gathering data at the natural summit of Llwynderw Hill

After five minutes data were gathered and stored, I closed the equipment down and sauntered back to join Linda and Nic sitting in the sunshine for a bite to eat and lots of good conversation. 

Nic engaging in an unusual self examination exercise!

We left the field and joined a public footpath leading to Cefn-hilin farm and then onward down the continuation of the lane to another public footpath which headed across fields, over a brook and then beside forestry.  It was beautiful.  It was also quiet and gave a sense of detachment from the world of Covid and lock down restrictions, with increasing warmth as late morning gave way to early afternoon. 

Our route toward Lower Pwll and the Red Lane

Friendly horse

The footpath led down to Lower Pwll and the Red Lane, which we happily followed past the entrance to Powis Castle and eventually back to our inward route on the canal towpath. 

The greens of late February

The walk took about seven hours and was very enjoyable and relaxed with good company, views, lots of laughs and another summit Trimbled.  It had been another good day on the hill!

 

Survey Result: 

 

Llwynderw Hill (significant name change)

Summit Height:  237.9m (converted to OSGM15, Trimble GeoXH 6000) 

Summit Grid Reference:  SJ 19600 03662 (Trimble GeoXH 6000) (summit relocation confirmed)

Bwlch Height:  159.7m (LIDAR)

Bwlch Grid Reference:  SJ 18827 03989 (LIDAR)

Drop:  78.3m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  32.89% (Trimble GeoXH 6000 summit and LIDAR bwlch) (Lesser Dominant deletion)

 

 

For further details please consult the Trimble Survey Spreadsheet