Mapping Mountains – Summit Relocations – 100m Twmpau

Twyn y Cryn (SO 325 008)

There has been confirmation of a Summit Relocation to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Twyn y Cryn (SO 325 008)

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

100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m 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.

100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Twyn y Cryn, and it is adjoined to the Cefn yr Ystrad group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and it is positioned with the A4042 road to the west and the A472 road to the north, and has the town of Pont-y-pŵl (Pontypool) towards its west and Brynbuga (Usk) towards its east.

When the original Welsh 100m P30 list was published on Geoff Crowder’s v-g.me website this hill was listed with twin tops with the prioritised summit positioned at SO 325 005, with an accompanying note stating Two tops of same height – other at SO 326 009.

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

The details for this hill were re-evaluated when the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map became available online, however both tops were given an uppermost 145m contour ring and no spot height, therefore the details relating to this hill remained the same.

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website

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 Twyn y Cryn (SO 325 008)

The height produced by LIDAR analysis to the natural summit of this hill is 148.3m positioned at SO 32531 00891,  this confirms the summit position and its relocation from its previously prioritised position originally given in the 100m P30 list of Geoff Crowder’s v-g.me website, and as such comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies to any listed hill whose summit meets the following criteria; where there are a number of potential summit positions within close proximity and the highest point is not where previously given, 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, or when the summit of the hill is in a different field compared to where previously given, or when 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.

Therefore, the height produced by LIDAR analysis is 148.3m and this is positioned at SO 32531 00891, this position is not given a spot height on contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and is approximately 350 metres northward from where the previously prioritised summit was listed.

The full details for the hill are:

Group:  Cefn yr Ystrad

Name:  Twyn y Cryn

OS 1:50,000 map:  171

Summit Height:  148.3m (LIDAR)

Summit Grid Reference (New Position):  SO 32531 00891 (LIDAR)

Bwlch Height:  113.0m (LIDAR)

Bwlch Grid Reference:  SO 32392 01153 (LIDAR)

Drop:  35.3m (LIDAR)

Myrddyn Phillips (September 2019)

Mapping Mountains – Hill Reclassifications – 100m Twmpau

Twyn y Cryn (SO 325 008) – 100m Sub-Twmpau reclassified to 100m Twmpau

There has been confirmation of a reclassification to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Twyn y Cryn (SO 325 008)

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

100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m 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.

100m Twmpau by Myrddyn Phillips

The name the hill is listed by is Twyn y Cryn, and it is adjoined to the Cefn yr Ystrad group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and it is positioned with the A4042 road to the west and the A472 road to the north, and has the town of Pont-y-pŵl (Pontypool) towards its west and Brynbuga (Usk) towards its east.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list that accompanied the main P30 list, as it did not meet the criteria then used in this list. 

When 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 35m of drop, based on an estimated c 147m summit height and an estimated c 112m bwlch height, with both heights based on interpolation of 10m contouring between 110m - 120m that appears on the Ordnance Survey 1:25,000 Explorer map.

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

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website became available online; and which is entitled the Interactive Coverage Map.  This mapping has additional spot heights not available on any other form of Ordnance Survey publicly available map, although no additional spot heights are given for this hill, this mapping does have contours at 5m intervals for this hill with bwlch contouring between 110m – 115m with an estimated bwlch height of c 112m and an uppermost summit contour of c 145 with an estimated summit height of c 147m, with these values confirming the interpolated values given this hill based on detail from the Ordnance Survey 1:25,000 Explorer map.

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website

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. 

Therefore, the confirmation of the reclassification of this hill from 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 148.3m summit height and a 113.0m bwlch height, with these values giving this hill 35.3m of drop which is sufficient for it to be classified as a 100m Twmpau.

The full details for the hill are:

Group:  Cefn yr Ystrad

Name:  Twyn y Cryn

OS 1:50,000 map:  171

Summit Height:  148.3m (LIDAR)

Summit Grid Reference:  SO 32531 00891 (LIDAR)

Bwlch Height:  113.0m (LIDAR)

Bwlch Grid Reference:  SO 32392 01153 (LIDAR)

Drop:  35.3m (LIDAR)

Myrddyn Phillips (September 2019)

Mapping Mountains – Significant Name Changes – 100m Twmpau

Twyn y Cryn (SO 325 008)

There has been a Significant Name Change to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Twyn y Cryn (SO 325 008)

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

100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m 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.

100m Twmpau by Myrddyn Phillips

The hill is adjoined to the Cefn yr Ystrad group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B5), and it is positioned with the A4042 road to the west and the A472 road to the north, and has the town of Pont-y-pŵl (Pontypool) towards its west and Brynbuga (Usk) towards its east.

The hill originally appeared in the 100m P30 liston Geoff Crowder’s v-g.me website under a transposed and partly invented, and transposed name of Maes-mawr / Pen Twyn y Cryn, with an accompanying note stating; Names from buildings to the South-West and wood to the North-West.  With these two names relating to what was considered the twin topped nature of this hill.

Maes-mawr / Pen Twyn y Cryn

140c

SO325005

171

152

Names from buildings to the South West & wood to the North-West.

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 a farm and also that of a wood and prefix the latter with the word Pen.  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

The summit of this hill has now been confirmed as that adjoined to Twyn y Cryn, and as this name is recorded on the Ordnance Survey series of Six-Inch maps and the contemporary Ordnance Survey 1:25,000 Explorer map and is appropriate for that of the hill, there is no reason why it should be prefixed with an invented word.

Therefore, the name this hill is now listed by in the 100m Twmpau is Twyn y Cryn, and this was derived from the Ordnance Survey series of Six-Inch maps and the contemporary Ordnance Survey 1:25,000 Explorer map.

The full details for the hill are:

Group:  Cefn yr Ystrad

Name:  Twyn y Cryn

Previously Listed Name:  Maes-mawr / Pen Twyn y Cryn 

OS 1:50,000 map:  171

Summit Height:  148.3m (LIDAR)

Summit Grid Reference:  SO 32531 00891 (LIDAR)

Bwlch Height:  113.0m (LIDAR)

Bwlch Grid Reference:  SO 32392 01153 (LIDAR)

Drop:  35.3m (LIDAR)

Myrddyn Phillips (September 2019)