Mapping Mountains – Significant Name Changes – 200m Twmpau

Pt. 277.7m (SO 106 406) 

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 Pt. 277.7m (SO 106 406)

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. 

200m Twmpau by Myrddyn Phillips

The hill 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 the A470 road to its east, and has the small community of Erwyd (Erwood) towards the north 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 not included in the accompanying Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

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 under the name of Cefn Gafros Common with an estimated c 18m of drop, based on the 275m summit spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map and an estimated c 257m bwlch height, based on interpolation of 10m contouring between 250m – 260m. 

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

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 use a prominent name that appeared close to the summit of the hill on the contemporary Ordnance Survey 1:25,000 Explorer map.  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.

However, on occasion even when research is conducted an appropriate name for the hill may not be found, and on such occasions the listing protocol is to use the point (Pt. 277.7m) notation, and for this hill this is such an example with the name of the Common applicable to land that does not take in the summit of this hill.

Therefore, the name this hill is now listed by in the 200m Twmpau is Pt. 277.7m, and this is being used as the author has not found an appropriate name for the hill either through historic research and/or local enquiry. 

 

The full details for the hill are:

Group:  Mynydd Epynt

Name:  Pt. 277.7m

Previously Listed Name:  Cefn Gafros Common   

OS 1:50,000 map:  148, 161

Summit Height:  277.7m (LIDAR) 

Summit Grid Reference:  SO 10666 40689 (LIDAR) 

Bwlch Height:  255.1m (LIDAR) 

Bwlch Grid Reference:  SO 10264 40290 (LIDAR) 

Drop:  22.6m (LIDAR) 

 

Myrddyn Phillips (August 2024)

 

  

Mapping Mountains – Significant Height Revisions – 200m Twmpau

 

Pt. 277.7m (SO 106 406) 

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 LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Pt. 277.7m (SO 106 406)

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. 

200m Twmpau by Myrddyn Phillips

The hill is being listed by the point (Pt. 277.7m) notation, 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 the A470 road to its east, and has the small community of Erwyd (Erwood) towards the north 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 not included in the accompanying Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

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 18m of drop, based on the 275m summit spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map and an estimated c 257m bwlch height, based on interpolation of 10m contouring between 250m – 260m. 

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 Pt. 277.7m (SO 106 406)

LIDAR analysis gives the summit of hill as 277.7m positioned at SO 10666 40689, and when compared to its originally listed summit height of 275m 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 277.7m and this was derived from LIDAR analysis, this is 2.7m higher than the originally listed summit height of 275m, which was based on the spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Mynydd Epynt 

Name:  Pt. 277.7m 

OS 1:50,000 map:  148, 161

Summit Height (New Height):  277.7m (LIDAR) 

Summit Grid Reference:  SO 10666 40689 (LIDAR) 

Bwlch Height:  255.1m (LIDAR) 

Bwlch Grid Reference:  SO 10264 40290 (LIDAR) 

Drop:  22.6m (LIDAR) 

 

Myrddyn Phillips (August 2024)

 

 

 

Mapping Mountains – Hill Reclassifications – 200m Twmpau

Pt. 277.7m (SO 106 406) – 200m Sub-Twmpau addition

There has been an addition to the list of 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 Pt. 277.7m (SO 106 406)

The criteria for the list that this addition 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. 

200m Twmpau by Myrddyn Phillips

The hill is being listed by the point (Pt. 277.7m) notation, 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 the A470 road to its east, and has the small community of Erwyd (Erwood) towards the north 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 not included in the accompanying Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

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 18m of drop, based on the 275m summit spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map and an estimated c 257m bwlch height, based on interpolation of 10m contouring between 250m – 260m. 

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.

Therefore, the addition of this hill to 200m Sub-Twmpau status is due to LIDAR analysis, resulting in a 277.7m summit height and a 255.1m bwlch height, with these values giving this hill 22.6m of drop, which is sufficient for it to be classified as a 200m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Epynt 

Name:  Pt. 277.7m 

OS 1:50,000 map:  148, 161

Summit Height:  277.7m (LIDAR) 

Summit Grid Reference:  SO 10666 40689 (LIDAR) 

Bwlch Height:  255.1m (LIDAR) 

Bwlch Grid Reference:  SO 10264 40290 (LIDAR) 

Drop:  22.6m (LIDAR) 

 

Myrddyn Phillips (August 2024)