Mapping Mountains – Hill Reclassifications – 700m Twmpau

700m Twmpau – Hill Reclassifications

The 700m Twmpau (thirty welsh metre prominences and upward) are the Welsh hills at or above 700m and below 800m in height that have a minimum drop of 30m.  Accompanying the main P30 list is a sub list entitled the 700m Sub-Twmpau with the qualification to this sub category being all Welsh hills at or above 700m and below 80om in height with 20m or more and below 30m of drop.  The Introduction to this list is linked in the above title.

The list is authored by Myrddyn Phillips and the posts that have appeared on Mapping Mountains detailing the additions, reclassifications and deletions to the main P30 list and the sub list appear below presented chronologically in receding order.

Mapping Mountains - Hill Reclassifications - 700m Twmpau

Pt. 714.3m (SH 827 359) – 700m Sub-Twmpau addition (5th reclassification)

Significant Height Revisions post for Pt. 714.3m

There has been an addition to the listing of the 700m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Aled Williams. 

LIDAR image of Pt. 714.3m (SH 827 359)

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

700m Twmpau - Welsh hills at or above 700m and below 800m in height with 30m minimum drop, with an accompanying sub list entitled the 700m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 700m and below 800m 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 list is authored by Myrddyn Phillips and is available to download in Google Doc format from Mapping Mountains.

The 700m Twmpau by Myrddyn Phillips

The hill is being listed by the point (Pt. 714.3m) notation and it is adjoined to the Arenig Fawr group of hills, which are situated in the central part of North Wales (Region A, Sub-Region A2), and it is positioned with a minor roads to the north, south-west and east, and the A4212 road farther to its north, and has the town of Y Bala towards the east.

When the list that later became known as the 700m Twmpau was first compiled, this hill was not included in the accompanying sub list due to an eye and spirit level survey conducted by John and Anne Nuttall that resulted in 60ft (18.3m) of drop, and it was originally listed with a 712m summit height based on the spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and a 694m bwlch height. 

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 700m Sub-Twmpau status is due to LIDAR analysis, resulting in a 714.3m summit height and a 693.6m bwlch height, with these values giving this hill 20.7m of drop, which is sufficient for it to be classified as a 700m Sub-Twmpau.

 

The full details for the hill are:

Group:  Arenig Fawr

Name:  Pt. 714.3m

OS 1:50,000 map:  124, 125

Summit Height:  714.3m (LIDAR) 

Summit Grid Reference:  SH 82741 35938 (LIDAR) 

Bwlch Height:  693.6m (LIDAR) 

Bwlch Grid Reference:  SH 82725 36128 (LIDAR) 

Drop:  20.7m (LIDAR)

 

Myrddyn Phillips (July 2023)

 

Mapping Mountains - Hill Reclassifications - 700m Twmpau

Pen y Gadair Fawr (SO 229 287) – 800m Twmpau reclassified to 700m Twmpau (4th reclassification)

There has been a reclassification to the listing of Twmpau (thirty welsh metre prominences and upward) hills due to analysis of LIDAR data by Aled Williams.  The hill was listed in the 800m height band of P30 Twmpau hills and it has now been reclassified to a 700m Twmpau.

The criteria for 700m Twmpau status is all Welsh hills at or above 700m and below 800m in height with 30m minimum drop, whilst the criteria for 800m Twmpau status is all Welsh hills at or above 800m and below 900m in height with 30m minimum drop.  Details to the 700m Twmpau were published on Mapping Mountains on 15^th April 2015, and details to the 800m Twmpau were published on Mapping Mountains on the 15^th March 2015.

The name of the hill is Pen y Gadair Fawr and it had been listed in the 800m height band of Twmpau hills, based on the 800m summit spot height that appears on Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps.  With the 800m height on Ordnance Survey maps originating from the 2624ft (799.8m) imperial bench mark height on the series of old Six-Inch maps.

The hill is situated on one of the central ridges that forms the Mynyddoedd Duon (Black Mountains) group of hills with its Cardinal Hill being Waun Fach (SO 215 299) and is placed in the Region of South Wales (Region C, Sub-Region C3).  It is situated between the steam valleys of the Grwyne Fawr to its north-east and the Grwyne Fechan to its south, with the town of Talgarth towards the north-west and Y Gelli Gandryll (Hay-on-Wye) towards the north.

As the hill is a part of designated open access land it can be accessed from most directions, however an extended circular walk taking in the ridge upon which it is positioned in conjunction with the ridge to its west is a good way to accustom oneself with this hill range.

The reclassification of Pen y Gadair Fawr to 700m Twmpau status is due to the analysis of LIDAR data by Aled Williams.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

Aled’s analysis of LIDAR data gives the hill the following details:

Pen y Gadair Fawr

Summit Height:  799.8m

Summit Grid Reference:  SO 22944 28758

Bwlch Height:  753.2m

Bwlch Grid Reference:  SO 22657 29359

Drop:  46.6m

Therefore, the 799.8m LIDAR data produced for the summit position at SO 22944 28758 and the 753.2m LIDAR data produced for the bwlch position at SO 22657 29359 gives this hill 46.6m of drop, and as the summit height is below 800m it is reclassified to a 700m Twmpau with a 799.8m summit height.

This now revises the total in the 800m and 700m Twmpau which will be updated accordingly.

The full details for the hill are:

Cardinal Hill:  Waun Fach

Summit Height:  799.8m (LIDAR data)

Name:  Pen y Gadair Fawr

OS 1:50,000 map:  161

Summit Grid Reference:  SO 22944 28758
  

Drop:  46.6m (LIDAR data)

Pen y Gadair Fawr (SO 229 287) now reclassified from an 800m Twmpau to a 700m Twmpau

My thanks to Aled Williams for sending the details of this hill to me

Myrddyn Phillips (October 2017)

Mapping Mountains - Hill Reclassifications - 700m Twmpau

Craig Eigiau (SH 713 654) – 700m Sub-Twmpau addition (3rd reclassification)

Survey post for Craig Eigiau

There has been an addition to the listing of the 700m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Leica RX1250 survey conducted by Alan Dawson, with a previous Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and Aled Williams having taken place.

Craig Eigiau (SH 713 654)

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

700m Twmpau - Welsh hills at or above 700m and below 800m in height with 30m minimum drop, with an accompanying sub list entitled the 700m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 700m and below 800m 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 list is authored by Myrddyn Phillips and is available to download in Google Doc format from Mapping Mountains.

700m Twmpau by Myrddyn Phillips

The name the hill is listed by is Craig Eigiau 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 with a minor road to its east and the B5106 road farther to its east, and has the small community of Tal-y-bont towards the north-east.

When the list that later became known as the 700m Twmpau was first compiled, this hill was not included in the accompanying sub list as it was listed with an estimated c 19m of drop, based on the 735m summit spot height that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 716m bwlch height, based on interpolation of 10 contouring between 710m - 720m. 

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

However, it was not until the Trimble GeoXH 6000 survey that the details for this hill could be accurately re-assessed.  This survey resulted in the hill being included as a 700m Sub-Twmpau.  The hill has now been surveyed by Alan Dawson with the Leica RX1250 and it is the height and position produced from this survey that is being prioritised.

The Trimble GeoXH 6000 gathering data at the summit of Craig Eigiau

Therefore, the addition of this hill to 700m Sub-Twmpau status is due to a Trimble GeoXH 6000 survey and a subsequent Leica RX1250 survey, resulting in a 735.0m summit height and a 714.1m bwlch height, with these values giving this hill 20.9m of drop, which is sufficient for it to be classified as a 700m Sub-Twmpau.

The full details for the hill are:

Group:  Carnedd Llywelyn

Name:  Craig Eigiau

OS 1:50,000 map:  115

Summit Height:  735.0m (converted to OSGM15, Leica RX1250)

Summit Grid Reference:  SH 71315 65425 (Leica RX1250) 

  

Bwlch Height:  714.1m (converted to OSGM15, Leica RX1250)

Bwlch Grid Reference:  SH 71191 65460 (Leica RX1250) 

Drop:  20.9m (Leica RX1250)

Myrddyn Phillips (July 2017)

Mapping Mountains - Hill Reclassifications - 700m Twmpau

Fan y Big (SO 036 206) - 700m Twmpau reclassified to 700m Sub-Twmpau (2nd reclassification)

1st survey post for Fan y Big

2nd survey post for Fan y Big

Significant Height Revisions post for Fan y Big

There has been a reclassification to the listing of Twmpau (thirty welsh metre prominences and upward) hills due to analysis of LIDAR data by Aled Williams.  The hill was listed in the 700m height band of P30 Twmpau hills and it has now been reclassified to a 700m Sub-Twmpau, with the criteria for the sub hills being 700m or more and below 800m in height with 20m or more and below 30m of drop.  Details to this height band of the Twmpau were published on the Mapping Mountains site on 15^th April 2015.

The hill had been listed with 30m of drop, based on the 719m summit spot height that appears on Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps and the 689m bwlch spot height that appears on the Ordnance Survey enlarged mapping hosted on the Geograph website. 

The hill is situated in the central part of the main ridge that forms the Bannau Brycheiniog (Brecon Beacons) group of hills with its Cardinal Hill being Pen y Fan (SO 012 215) and is placed in the Region of South Wales (Region C, Sub-Region C2).  It is situated between the towns of Aberhonddu (Brecon) to its north and Merthyr Tudful to its south.

The hill can be accessed from public footpaths originating from its north and from its south; or it can be combined as a longer expedition taking in the main Bannau Brycheiniog ridge either from its west or from its east.

The name of the hill is Fan y Big and its reclassification to a 700m Sub-Twmpau is due to the analysis of LIDAR data by Aled Williams.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

Aled’s analysis of LIDAR data gives the hill the following details:

Fan y Big

Summit Height:  716.3m

Summit Grid Reference:  SO 03651 20662

Bwlch Height:  688.1m

Bwlch Grid Reference:  SO 03773 19876

Drop:  28.2m

Therefore, the 716.3m LIDAR data produced for the summit position at SO 03651 20662 and the 688.1m LIDAR data produced for the bwlch position at SO 03773 19876 is sufficient for this hill to be reclassified from a 700m Twmpau to a 700m Sub-Twmpau with 28.2m of drop.

This now revises the total in the 700m Twmpau which will be updated accordingly.

The full details for the hill are:

Cardinal Hill:  Pen y Fan

Summit Height:  716.3m (LIDAR data)

Name:  Fan y Big

OS 1:50,000 map:  160

Summit Grid Reference:  SO 03651 20662 

  

Drop:  28.2m (LIDAR data)

Fan y Big (SO 036 206) now reclassified to a 700m Sub-Twmpau

My thanks to Aled Williams for analysing the details of this hill

For details on the first survey of Fan y Big

For details on the second survey of Fan y Big

Myrddyn Phillips (March 2017)

Mapping Mountains - Hill Reclassifications - 700m Twmpau

Bera Mawr (SH 674 682) - 700m Twmpau reclassified to 700m Sub-Twmpau (1st reclassification)

Survey post for Bera Mawr

There has been a deletion to the listing of the 700m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and a subsequent Leica RX1250 survey conducted by Alan Dawson. 

Bera Mawr (SH 674 682)

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

700m Twmpau - Welsh hills at or above 700m and below 800m in height with 30m minimum drop, with an accompanying sub list entitled the 700m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 700m and below 800m 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 list is authored by Myrddyn Phillips and is available to download in Google Doc format from Mapping Mountains.

700m Twmpau by Myrddyn Phillips

The name the hill is listed by is Bera Mawr 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 with the A55 road to to its north and the A5 road towards its south-west, and has the town of Llanfairfechan towards the north.

When the list that became known as the 700m Twmpau was first compiled, this hill was included in the main list with an estimated c 31m of drop, based on the 794m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 763m bwlch height, based on interpolation of 10m contouring between 760m – 770m.

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

However, it was not until the Trimble GeoXH 6000 survey that the details for this hill could be accurately re-assessed.  This survey resulted in a 793.6m summit height and a 763.9m bwlch height, with these values giving this hill 29.7m of drop.  The hill has subsequently been surveyed by Alan Dawson using the Leica RX1250, with the resulting summit height being prioritised for the listed values of this hill.

The Trimble GeoXH 6000 gathering data at the summit of Bera Mawr

Therefore, the reclassification of this hill to 700m Sub-Twmpau status is due to a Trimble GeoXH 6000 survey with a subsequent Leica RX1250 summit survey being prioritised for listing purposes, resulting in a 793.7m summit height and a 763.9m bwlch height, with these values giving this hill 29.8m of drop, with is insufficient for it to be classified as a 700m Twmpau. 

The full details for the hill are:

Group:  Carnedd Llywelyn

Name:  Bera Mawr

OS 1:50,000 map:  115

Summit Height:  793.7m (converted to OSGM15, Leica RX1250)

Summit Grid Reference:  SH 67482 68271 (Leica RX1250)

Bwlch Height:  763.9m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SH 67513 68149 (Trimble GeoXH 6000)

Drop:  29.8m (Leica RX1250 summit and Trimble GeoXH 6000 bwlch)

Myrddyn Phillips (March 2014)