Mapping Mountains – Trimble Surveys – Carnedd Wen

30.04.25  Castell Dolforwyn (SO 151 950) 

Castell Dolforwyn (SO 151 950)

With the weather set fine, my cousin Lynn, wanted to visit Castell Dolforwyn.  We’d spoken about the castle on a number of occasions over recent years, but up until now had not fixed a date to visit.  It was going to be a family outing as we had mentioned this to another cousin; Thelma, and she also wanted to visit.

It proved an extremely warm day and especially so during the afternoon.  We set off walking at 2.00pm from the small car park directly east of the summit.  It’s only a short walk from here to the remains of the castle, but today with the heat of the afternoon it was going to be a slow plod to the top. 

Information board giving detail of the castle's construction

Llywelyn ap Gruffydd built the castle in 1273 on the Welsh side of the Afon Hafren (River Severn), with Montgomery castle a few miles away on the English side of the river, with this being part of the lordships associated with the English crown.

Its occupation by Llywelyn was short lived, as defiance toward the English crown resulted in a siege, with its surrender in 1277.  Afterward it was occupied and reinforced by Marcher Lord Roger Mortimer, before falling in to disrepair and abandonment in the 14^th century.  Today it stands on a quiet Welsh hill top looking out toward border country. 

Information board giving detail of the later renervation

On my previous visit I had Trimbled the summit, therefore today was purely set aside for an afternoon with my cousins, with good conversation and lots of laughs.  A steep track leads from the car park toward a gate and an earthen track beyond, thankfully the majority of which was in shade.  The dappled light and increasing warmth gave a Mediterranean feel to the whole walk. 

The path leading to the old entrance gate

Reaching the outer perimeter of the castle a grassed bank leads through what was once the gateway entrance, to the remaining walls and enclosed rooms within.  Today we had the castle to ourselves for the majority of our visit, with the only other visitors being a mother and her two young children, who were on holiday from Belgium exploring Wales for the week in a large camper van.  They had visited the Gower, Pembrokeshire, Anglesey, Yr Wyddfa and were heading down to Brecon before flying home from Bristol tomorrow morning.  They had certainly picked a glorious week to visit. 

Thelma beside the wall

Having roamed the interior of the castle we did a loop of the exterior walls before heading back inside the castle remains, where we found a suitable place to sit and relax in shade away from what was proving a quite ferocious sun.  We remained here for about 20 minutes, cooling down and chatting. 

Lynn admiring the view

All that remained was a steady walk back down our inward route to the awaiting car, where I changed from walking boots to sandals before driving the short distance back to Welshpool. 

 

Survey Result:

 

Castell Dolforwyn (significant name change)  

Summit Height:  228.5m (converted to OSGM15, previous Trimble GeoXH 6000 survey) (significant height revision)

Summit Grid Reference:  SO 15189 95016 (previous Trimble GeoXH 6000 survey)

Bwlch Height:  188.1m (LIDAR)

Bwlch Grid Reference:  SO 14988 95278 (LIDAR)

Drop:  40.4m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  17.68% (Trimble GeoXH 6000 summit and LIDAR bwlch)

                                       

 

For details on the summit survey of Castell Dolforwyn

For further details please consult the Trimble Survey Spreadsheet 

Mapping Mountains – Significant Name Changes – 200m Twmpau

Castell Dolforwyn (SO 151 950) 

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 a Trimble GeoXH 6000 survey and LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Castell Dolforwyn (SO 151 950)

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 that have 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 southern part of North Wales (Region A, Sub-Region A3), and it is positioned encircled by minor roads, with the B4389 road farther to its south-west and the A483 road farther to its south-east, and has the town of Y Drenewydd (Newtown) towards the south-west.

The hill appeared in the original Welsh 200m P30 list on Geoff Crowder’s v-g.me website, under the transposed name of Dolforwyn Castle, with an accompanying note stating; Name from remains of castle at summit.

Dolforwyn Castle

230c

SO152951

136

215

Name from remains of castle at summit

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 a bilingual name that appears on contemporary Ordnance Survey maps and use it for that of the hill.  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

Since the original publication of the Welsh P30 lists on Geoff Crowder’s v-g.me website there have been a number of maps made available online.  Some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website.  Whilst others were digitally updated such as the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map, whilst others are current and digitally updated such as the interactive mapping on the Magic Maps and WalkLakes websites.  One of the historic maps now available online is the Ordnance Survey Draft Surveyors map which formed the basis for the first publicly available Ordnance Survey One-Inch ‘Old Series’ map, and it is the Draft Surveyors map and the prioritised language protocol that has prompted the change in the listed name of this hill.

The Draft Surveyors maps consist of the preliminary drawings made by the Ordnance Survey surveyors between the 1780s and 1840 and formed the basis for the first publicly available One-Inch map.  They were drawn at scales of six inches to the mile for areas considered of particular military significance and down to two inches to the mile for other areas.  Fair copies were then produced from these preliminary drawings to one inch to the mile and then copper plates were prepared for printing.  The Draft Surveyors maps for the whole of Wales are now available online and they form an important part in the study of Welsh upland place-names as they bridge the time frame between the late 18^th century and the mid-19^th century when the Ordnance Survey produced their first One-Inch maps, and importantly for this hill and its listed name, it is this map that uses the name of Castell Dolforwyn. 

Extract from the Ordnance Survey Draft Surveyors map

The intricacies of language and prioritising one in favour of another for listing a hill is fraught with complication, with originating Cymraeg names being anglicised and also originating English names being cymricised, examples such as these are more common in border country and especially so for anglicised forms.  There is no steadfast rule that fits all, but as a standard a name that has its origins in the Welsh language and where this is substantiated by either historic documentation and/or contemporary usage should be prioritised in favour of a contemporary anglicised or English version of the name.  Likewise, if a name exists where an element of it is in English and if this name applies to a hill that is situated in a Welsh speaking part of Wales it is standard practice to use a full Welsh term for the name.  It is also standard practice to use a Welsh name for a hill if another name exists that has originated in a different language.

Therefore, the name this hill is now listed by in the 200m Twmpau is Castell Dolforwyn, and this was derived from the Ordnance Survey Draft Surveyors map with the prioritised language protocol being used. 

 

The full details for the hill are:

Group:  Carnedd Wen

Name:  Castell Dolforwyn

Previously Listed Name:  Dolforwyn Castle   

OS 1:50,000 map:  136

Summit Height:  228.5m (Trimble GeoXH 6000) 

Summit Grid Reference:  SO 15189 95016 (Trimble GeoXH 6000) 

Bwlch Height:  188.1m (LIDAR) 

Bwlch Grid Reference:  SO 14988 95278 (LIDAR) 

Drop:  40.4m (Trimble GeoXH 6000 summit and LIDAR bwlch) 

 

Myrddyn Phillips (November 2023)

  

Mapping Mountains – Significant Height Revisions – 200m Twmpau

Castell Dolforwyn (SO 151 950) 

There has been a Significant Height Revision 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 a Trimble GeoXH 6000 survey and LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Castell Dolforwyn (SO 151 950)

The criteria for the list that this height revision 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 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 name the hill is now listed by is Castell Dolforwyn, and it is adjoined to the Carnedd Wen group of hills, which are situated in the southern part of North Wales (Region A, Sub-Region A3), and it is positioned encircled by minor roads, with the B4389 road farther to its south-west and the A483 road farther to its south-east, and has the town of Y Drenewydd (Newtown) towards the south-west.

When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was listed with a summit height of c 23om, with this being the uppermost contour on the contemporary Ordnance Survey 1:25,000 Explorer map. 

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

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 an estimated c 43m of drop, based on the 231m summit spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map and an estimated c 188m bwlch height, based on interpolation of 5m contouring between 185m – 190m that also appeared on this mapping. 

The Trimble GeoXH 6000 gathering data at the summit of Castell Dolforwyn

However, it was not until the Trimble GeoXH 6000 survey that the details for this hill could be accurately re-assessed.  The summit height produced by this survey is 228.5m and is positioned at SO 15189 95016, 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 228.5m and this was derived from a Trimble GeoXH 6000 survey, this is 2.5m lower than the previously listed summit height of 231m, which was based on the spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Carnedd Wen 

Name:  Castell Dolforwyn 

OS 1:50,000 map:  136

Summit Height (New Height):  228.5m (Trimble GeoXH 6000) 

Summit Grid Reference:  SO 15189 95016 (Trimble GeoXH 6000) 

Bwlch Height:  188.1m (LIDAR) 

Bwlch Grid Reference:  SO 14988 95278 (LIDAR) 

Drop:  40.4m (Trimble GeoXH 6000 summit and LIDAR bwlch) 

 

Myrddyn Phillips (November 2023)

 

 

 

 

 

  

Mapping Mountains – Trimble Surveys – Carnedd Wen

06.09.23  Castell Dolforwyn (SO 151 950) 

Castell Dolforwyn (SO 151 950)

Castell Dolforwyn sits atop a hill that from the near main road is shrouded by trees.  I had only visited once before; in February 2004 when combining this hill with a number of other P30s to its north-west.  Other than prior knowledge of its position and/or the small signpost pointing toward it from the road to its east, it would be all too easy not to know that one of Wales’ most important ancient castles is positioned near-by. 

Text from the information board at the small car park

The castle was built in 1273 by Llywelyn ap Gruffydd on the Welsh side of the Afon Hafren (River Severn), with the castle at Montgomery only a few miles away on the English side of the river and very much a part of the lordships associated with the English crown.

The information board beside the narrow lane leading to the small car park

Its occupation by Llywelyn was short lived as defiance toward the English crown resulted in a siege and following surrender of the castle in 1277.  It was then occupied and reinforced by Marcher Lord Roger Mortimer, before falling in to disrepair and abandonment in the 14^th century.  Today its remains are evocative, standing as one of the last vestiges of Welsh Princedom in this part of the country. 

A brief history of the castle

With business to attend to in Newtown and the prospect of a forested top to visit this upcoming Saturday, and the forecast for warm conditions I thought a small walk to a single hill on my way home to Welshpool was in order, and Castell Dolforwyn ticked all boxes.

I pulled up at the small parking area to the east of the summit and was walking by 10.15am.  The path from this direction leads through a gate and then steeply up a track with embedded stone giving grip for vehicle access to Yewtree Cottage, which could be seen clinging to the hillside from the car park below. 

One of many butterflies flitting about in the morning's sun

The hedgerows were awash in greenery with a myriad of butterflies flitting about in the morning sun.  The track veered leftward and then gradually gained height until beside the cottage, from here a gate accesses the upper track which eventually leads to the remains of the castle. 

The track leading to the castle

The sky was ablaze with blue as I approached the stone work of the exterior walls, it was already warm and I was glad that the uphill was now over with.  Prior to the visit I had used LIDAR to determine the height and position of the summit and its connecting bwlch and had come prepared with the relevant ten figure grid references.

LIDAR gives two high points 1.1cm apart in height.  The first one that I approached looked higher.  However, it is reported that the upper hill was levelled to accommodate the building of the castle, so any semblance of a natural high point is only what remains today.  Before positioning the Trimble to gather its first data set I wandered parts of the castle and looked back toward the spot the Trimble was now placed upon, and it was soon set to gather its allotted data. 

Gathering data at the summit of Castell Dolforwyn

This high point matched the LIDAR co-ordinates for the summit.  As the Trimble quietly beeped away gathering its all-important summit data I sat on one of the stone walls and waited for the five minutes of data to be stored.

Once data were gathered and stored I closed the equipment down and immediately activated it again as I headed toward the second LIDAR top, this proved to be on a gravelled section at the north-easterly part of the castle, I quickly dismissed this as unnatural and backtracked to a slight grassy rise between the two points. 

LIDAR summit image of Castell Dolforwyn

This second position is given lower by LIDAR, but now here I wanted a comparison of Trimble data with the gravelled section dismissed as a recent man-made construct.  During data collection the castle surrounds remained quiet, with only the occasional sound of a bird and the tree scampering of a squirrel. 

Gathering data at the second point surveyed with the Trimble GeoXH 6000

Once the equipment was packed away I wandered around the castle, reading the various information boards as I did so.  Leaving the inner castle I then walked the perimeter of the exterior walls at their immediate base.  This gave a good and different perspective to the castle and I would recommend doing this to any visitor. 

Part of the exterior wall

An information board in the interior of the castle

The south-west corner of the castle

By the time I left and headed back down the rack it was getting increasing warmer, but I was in no rush and the going was easy.  Back at my car I talked with a Dutch couple who were touring Wales for the week.  We chatted for ten minutes or more before they set off up the steep track toward the castle; I recommended taking lots of water as it was now decidedly hot.  

 

Survey Result:

 

Castell Dolforwyn (significant name change)

Summit Height:  228.5m (Trimble GeoXH 6000) (significant height revision)

Summit Grid Reference:  SO 15189 95016 (Trimble GeoXH 6000)

Bwlch Height:  188.1m (LIDAR)

Bwlch Grid Reference:  SO 14988 95278 (LIDAR)

Drop:  40.4m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  17.68% (Trimble GeoXH 6000 summit and LIDAR bwlch)

                                       

For details on the 2nd visit to Castell Dolforwyn

For further details please consult the Trimble Survey Spreadsheet