Mapping Mountains – Significant Height Revisions – Y Trichant – The 300m Hills of Wales

Glynllugwy (SH 754 592) 

There has been a Significant Height Revision to a hill that is listed in the 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 Glynllugwy (SH 754 592)

The criteria for the list that this height revision 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 13^th May 2017, and the Introduction to the Mapping Mountains publication of the list appearing on the 1^st January 2022. 

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

The name the hill is now listed by is Glynllugwy, and this was derived from the Tithe map, and it is adjoined to the Carnedd Llywelyn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned between Llyn Bychan to its west, Llyn Goddionduon to its south and Llyn Bodgynydd to its east, with the A5 road to its south and the B5106 road, the Afon Conwy and the A470 road to its east, and has the village of Capel Curig towards the west south-west and the village of Betws-y-coed 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 included in the main P30 list with a non interpolated summit height of c 310m, based on the uppermost contour on the contemporary 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 40m of drop, based on an estimated c 313m summit height and an estimated c 273m bwlch height, with both heights based on interpolation of 10m contouring. 

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

One of the resources recently available online is the mapping on the OS Maps website and the details for this hill were subsequently re-assessed against this mapping.  This is the replacement for OS Get-a-map and until recent times had contours at 5m intervals which were proving consistently more accurate compared to the 5m contours that sometimes appear on the Ordnance Survey 1:25,000 Explorer map and used to appear on the online Vector Map Local.  This mapping had an uppermost 305m contour ring and bwlch contouring between 270m – 275m, with interpolation placing the height of the summit as c 309m and the height of th e bwlch as c 271m, with these values giving this hill as estimated c 38m of drop.

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 summit image of Glynllugwy (SH 754 592)

The summit height produced by LIDAR analysis is 318.4m and is positioned at SH 75484 59240, 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, Harvey or other interactive 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 with the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 318.4m and this was derived from LIDAR analysis, this is 5.4m higher than the estimated c 313m summit height, which was based on interpolation of the uppermost 310m contour that appears on the Ordnance Survey 1:25,000 Explorer map, and 9.4m higher than the estimated c 309m summit height, which was based on interpolation of the uppermost 305m contour that appeared on the interactive mapping hosted on the OS Maps website. 

 

The full details for the hill are: 

Group:  Carnedd Llywelyn 

Name:  Glynllugwy 

OS 1:50,000 map:  115

Summit Height (New Height):  318.4m (LIDAR)                                                           

Summit Grid Reference:  SH 75484 59240 (LIDAR) 

Bwlch Height:  270.4m (LIDAR) 

Bwlch Grid Reference:  SH 75296 59502 (LIDAR) 

Drop:  48.1m (LIDAR) 

 

Myrddyn Phillips (February 2025)

 

 

  

Mapping Mountains – Summit Relocations – 200m Twmpau

 

Cae Gwar y Tŷ (SO 035 495) 

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 conducted by Myrddyn Phillips. 

LIDAR image of Cae Gwar y Tŷ (SO 035 495)

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 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.  The list is authored by Myrddyn Phillips, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

200m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Cae Gwar y Tŷ, and this was derived from the Tithe map, and it is adjoined to the Mynydd Epynt group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with a minor road to its west and immediate east, and the B4520 road farther to its east, and has the town of Llanfair-ym-Muallt (Builth Wells) towards the north.

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 with a 235m summit height, based on the spot height that appears on 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 37m of drop, based on the 235m summit spot height positioned at SO 03503 49545 and the 198m bwlch spot height that appears on the Ordnance Survey 1:50,000 Landranger and 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 gives the highest ground on this hill as 232.84m positioned at SO 03504 49538.  However, this is a part of a raised field boundary and protocols dictate that as this is deemed a relatively recent man-made construct such ground is discounted from the height of a hill. 

LIDAR summit image of Cae Gwar y Tŷ (SO 035 495)

The height produced by LIDAR analysis to the natural summit of this hill is 232.81m and this is positioned at SO 03502 49537 and SO 03504 49535, and this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour either on Ordnance Survey maps or interactive mapping, to a different point where a number of potential summit positions are within close proximity, 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 or covered reservoir that is considered 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.

Therefore, the summit height produced by LIDAR analysis is 232.81m and this is positioned at SO 03502 49537 and SO 03504 49535, and this position is approximately three metres west south-westward from the high point of the raised field boundary. 

 

The full details for the hill are: 

Group:  Mynydd Epynt 

Name:  Cae Gwar y Tŷ                  

OS 1:50,000 map:  147

Summit Height:  232.8m (LIDAR) 

Summit Grid Reference (New Position):  SO 03502 49537 & SO 03504 49535 (LIDAR) 

Bwlch Height:  198.4m (LIDAR) 

Bwlch Grid Reference:  SO 03391 49083 (LIDAR) 

Drop:  34.4m (LIDAR) 

 

Myrddyn Phillips (February 2025)

 

Mapping Mountains – Significant Height Revisions – The Fours – The 400m Hills of England

 

Belles Knott (NY 297 085) 

There has been a Significant Height Revision to a hill that is listed in the The Fours – The 400m Hills of England, with the summit height, col height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Belles Knott (NY 297 085)

The criteria for the list that this height revision applies to are:

The Fours – The 400m Hills of England - English hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list is a sub list entitled the Sub-Fours, the criteria for which are all English hills at or above 400m and below 500m in height that have 15m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is available to download in Google Doc format from the Mapping Mountains site.

The Fours - The 400m Hills of England by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Belles Knott, and it is adjoined to the High Raise group of hills, which are situated in the Lake District, and it is positioned with the B5343 road to its south and the A591 road to its east, and has the village of Grasmere towards the east.

When the Introduction to the first group of hills for the updated and revised listing of the The Fours – The 400m Hills of England was published by Mapping Mountains on the 10^th September 2022, it was announced that the accompanying sub lists were being revised with the two 390m categories dispensed with and the criteria and name of the 400m Sub-Fours revised.  The one accompanying sub list is now named the Sub-Fours with its criteria being all English hills 400m and above and below 500m in height that have 15m and more and below 30m of drop.

Prior to this revision this hill was listed with an estimated c 21m of drop, based on an estimated c 493m summit height and an estimated c 472m col height, with both heights based on interpolation of 5m contouring that appeared on the interactive mapping hosted on the OS Maps website. 

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 summit image of Belles Knott (NY 297 085)

LIDAR analysis gives the height of this hill as 490.6m positioned at NY 29711 08585, and when compared to its originally listed summit height 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, Harvey or other interactive 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 with the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 490.6m and this was derived from LIDAR analysis, this is 2.4m lower than the originally listed c 493m summit height, which was based on interpolation of 5m contouring that appeared on the interactive mapping hosted on the OS Maps website. 

 

The full details for the hill are:

Group:  High Raise

Name:  Belles Knott

OS 1:50,000 map:  89, 90

Summit Height (New Height):  490.6m (LIDAR)

Summit Grid Reference:  NY 29711 08585 (LIDAR)

Col Height:  471.65m (LIDAR)

Col Grid Reference:  NY 29595 08661 (LIDAR)

Drop:  18.9m (LIDAR)

 

Myrddyn Phillips and Aled Williams (February 2025)

 

 

Mapping Mountains – Significant Name Changes – 200m Twmpau

Bigni (SN 199 311) 

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 conducted by Myrddyn Phillips. 

LIDAR image of Bigni (SN 199 311)

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.  The list is authored by Myrddyn Phillips, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

200m Twmpau by Myrddyn Phillips

The hill is adjoined to the Mynydd Preseli group of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north, south and east, and the A478 road to its west, and has the village of Crymych towards the north-west.

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 under the transposed name of Bryn-eithin, with an accompanying note stating; Name from building to the South.

Bryn-eithin

263m

SN199311

145

35

Name from buildings to the South

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, with little consideration for the meaning of the name and where it was appropriately applied to.  My preference was to use farm names and put Pen, Bryn or Moel in front of them or as in this instance transpose a name of a farm 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, and it is the series of Ordnance Survey Six-Inch maps that form the basis of the change in the listed name of this hill.

The Ordnance Survey series of Six-Inch maps formed the base map Ordnance Survey used for many decades leading to the production of the 1:10,000 Series of maps, both have now been superseded by the digitised Master Map.  The series of Six-Inch maps are excellent for name placement and especially so compared to the contemporary Ordnance Survey 1:25,000 Explorer map, and it is the series of Six-Inch maps that position the name of Begney adjacent to the summit of this hill.

Extract from the Ordnance Survey series of Six-Inch maps

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.  With online sources, including Coflein giving the alternate name of Bigni.

Therefore, the name this hill is now listed by in the 200m Twmpau is Bigni, and this was derived from the Ordnance Survey series of Six-Inch maps, with the language protocol also being used. 

 

The full details for the hill are:

Group:  Mynydd Preseli

Name:  Bigni

Previously Listed Name:  Bryn-eithin   

OS 1:50,000 map:  145

Summit Height:  262.9m (LIDAR) 

Summit Grid Reference:  SN 19911 31149 (LIDAR) 

Bwlch Height:  211.8m (LIDAR) 

Bwlch Grid Reference:  SN 19869 31901 (LIDAR) 

Drop:  51.1m (LIDAR) 

 

Myrddyn Phillips (February 2025)