Mapping Mountains – Hill Reclassifications – 500m Twmpau

Esgair Saeson (SN 795 603) – 500m Sub-Twmpau deletion

There has been a deletion to the listing of the 500m 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 imge of Esgair Saeson (SN 795 603)

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

500m Twmpau - Welsh hills at or above 500m and below 600m in height with 30m minimum drop, with an accompanying sub list entitled the 500m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 500m and below 600m 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 500m Twmpau by Myrddyn Phillips

The name the hill is listed by is Esgair Saeson and it is adjoined to the Esgair Wen 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 north-west and south, and has the small community of Pontrhydfendigaid towards the north-west and the town of Tregaron towards the west.

After the list that later became known as the 500m Twmpau was first compiled, this hill was included in the accompanying sub list with an estimated c 24m of drop, based on the 500m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 476m bwlch height, based on interpolation of 10m contouring between 470m – 480m. 

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

Since the original compilation of this list 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.

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had a 475m bwlch spot height positioned at SN 79101 60658, and when coupled with its 500m summit spot height these values gave this hill 25m of drop.

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 bwlch contouring between 470m – 475m, with interpolation placing the height of the bwlch as an estimated c 473m, resulting in its drop value being amended to an estimated c 27m.

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 deletion of this hill from 500m Sub-Twmpau status is due to LIDAR analysis, resulting in a 498.4m summit height and a 473.8m bwlch height, with these values giving this hill 24.6m of drop, with its height insufficient for it to be classified as a 500m Sub-Twmpau. 

 

The full details for the hill are:

Group:  Esgair Wen

Name:  Esgair Saeson

OS 1:50,000 map:  146, 147

Summit Height:  498.4m (LIDAR)

Summit Grid Reference:  SN 79504 60391 (LIDAR)

Bwlch Height:  473.8m (LIDAR)

Bwlch Grid Reference:  SN 79174 60567 (LIDAR)   

Drop:  24.6m (LIDAR) 

 

Myrddyn Phillips (November 2023)

 

  

Mapping Mountains – Hill Reclassifications – 500m Twmpau

Esgair Llyn Du (SN 769 620) – 500m Sub-Twmpau deletion

There has been a deletion to the listing of the 500m 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. 

Esgair Llyn Du (SN 769 620)

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

500m Twmpau - Welsh hills at or above 500m and below 600m in height with 30m minimum drop, with an accompanying sub list entitled the 500m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 500m and below 600m 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 500m Twmpau by Myrddyn Phillips

The name the hill is listed by is Esgair Llyn Du and it is adjoined to the Esgair Wen 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 north-west and south, and has the small community of Pontrhydfendigaid towards the north-west and the town of Tregaron towards the west south-west. 

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

After the list that later became known as the 500m Twmpau was first compiled, this hill was included in the accompanying sub list with 20m of drop, based on the 534m summit spot height positioned at SN 767 617 and the 514m bwlch spot heights that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map, with this mapping giving two positions of equal height for the bwlch. 

Extract from the interactive mapping hosted on the WalkLakes website

The Ordnance Survey Vector Map Local hosted on the Geograph website gave the higher spot height to the middle of three larger 530m map contour rings, with the southerly and middle ring contours subsequently surveyed with the Trimble GeoXH 6000.  However, the interactive mapping hosted on the WalkLakes website indicates that the most northerly of these is the higher. 

The Trimble GeoXH 6000 set-up position at the southerly of the three tops

The Trimble GeoXH 6000 set-up position at the middle of the three tops

At the northerly of the three tops and the summit of Esgair Llyn Du

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 image of Esgair Llyn Du (SN 769 620)

Therefore, the deletion of this hill from 500m Sub-Twmpau status is due to LIDAR analysis, resulting in a 532.8m summit height and a 513.8m bwlch height, with these values giving this hill 19.0m of drop, which is insufficient for it to be classified as a 500m Sub-Twmpau.

 

The full details for the hill are:

Group:  Esgair Wen

Name:  Esgair Llyn Du

OS 1:50,000 map:  146, 147

Summit Height:  532.8m (LIDAR) 

Summit Grid Reference:  SN 76930 62044 (LIDAR) 

Bwlch Height:  513.8m (LIDAR) 

Bwlch Grid Reference:  SN 76942 61196 (LIDAR) 

Drop:  19.0m (LIDAR)

 

Myrddyn Phillips (November 2023)

 

 

  

Mapping Mountains – Hill Reclassifications – 500m Twmpau

Carreg y Big (SH 927 201) – 500m Sub-Twmpau deletion

There has been a deletion to the listing of the 500m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail produced by Joe Nuttall in his surface analysis progamme, with subsequent LIDAR analysis conducted by the DoBIH team and independently by Myrddyn Phillips. 

LIDAR image of Carreg y Big (SH 927 201)

The criteria for the list that this deletion applies to are:500m Twmpau - Welsh hills at or above 500m and below 600m in height with 30m minimum drop, with an accompanying sub list entitled the 500m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 500m and below 600m 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 500m Twmpau by Myrddyn Phillips

The name the hill is listed by is Carreg y Big and it is adjoined to the Esgeiriau Gwynion group of hills, which are situated in the southern part of North Wales (Region A, Sub-Region A3), and it is positioned with a minor road to its north and west, and the B4393 road to its east north-east, and has the village of Llanwddyn towards the east.

When the list that later became known as the 500m Twmpau was first compiled, this hill was included in the accompanying sub list with an estimated c 21m of drop, based on the 589m summit height that appears on the contemporary Ordnance Survey 1:25,000 Outdoor Leisure map, and an estimated c 568m bwlch height, based on interpolation of 10m contouring between 560m – 570m. 

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 and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had a 569m bwlch spot height, and therefore the drop value was revised to 20m.

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 deletion of this hill from 500m Sub-Twmpau status is due to LIDAR analysis, resulting in a 589.4m summit height and a 569.8m bwlch height, with these values giving this hill 19.6m of drop, which is insufficient for it to be classified as a 500m Sub-Twmpau.

 

The full details for the hill are:

Group:  Esgeiriau Gwynion

Name:  Carreg y Big

OS 1:50,000 map:  125

Summit Height:  589.4m (LIDAR) 

Summit Grid Reference:  SH 92712 20119 (LIDAR) 

Bwlch Height:  569.8m (LIDAR) 

Bwlch Grid Reference:  SH 92769 19949 & SH 92769 19953 (LIDAR) 

Drop:  19.6m (LIDAR)

 

Myrddyn Phillips (August 2023)

 

  

Mapping Mountains – Hill Reclassifications – 500m Twmpau

 

Pt. 551.8m (SH 665 322) – 500m Sub-Twmpau addition

There has been an addition to the listing of the 500m 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. 551.8m (SH 665 322)

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

500m Twmpau - Welsh hills at or above 500m and below 600m in height with 30m minimum drop, with an accompanying sub list entitled the 500m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 500m and below 600m 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 500m Twmpau by Myrddyn Phillips

The hill is being listed by the point (Pt. 551.8m) notation and it is adjoined to the Y Llethr group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A2), and it is positioned with the B4573 road to its west, the A470 road to its east, and has a minor road to its west south-west, and has the village of Trawsfynydd towards the north-east.

When the list that later became known as the 500m Twmpau was first compiled, this hill was not included in the accompanying sub list due to a basic levelling survey conducted by Myrddyn Phillips on the 31^st August 2004 that resulted in 63ft (19.2m) of drop, and it was originally listed with an estimated c 552m summit height and an estimated c 533m bwlch height, with both heights based on interpolation of 10m contouring. 

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

Since the original compilation of this list 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.

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and for this hill it had a 551m summit spot height positioned at SH 66591 32219.

One of the mapping resources now available online is the WalkLakes website which hosts an interactive map originated from the Ordnance Survey Open Data programme.  This map has many spot heights not on other publicly available maps and for this hill it has two 512m summit spot heights which enabled the numerical detail to be updated, but with 19.2m of listed drop it was still not included as a 500m Sub-Twmpau. 

Extract from the interactive mapping hosted on the WalkLakes 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 addition of this hill to 500m Sub-Twmpau status is due to LIDAR analysis, resulting in a 551.8m summit height and a 531.7m bwlch height, with these values giving this hill 20.1m of drop, which is sufficient for it to be classified as a 500m Sub-Twmpau.

 

The full details for the hill are:

Group:  Y Llethr

Name:  Pt. 551.8m

OS 1:50,000 map:  124

Summit Height:  551.8m (LIDAR) 

Summit Grid Reference:  SH 66588 32216 (LIDAR) 

Bwlch Height:  531.7m (LIDAR) 

Bwlch Grid Reference:  SH 66333 32260 (LIDAR) 

Drop:  20.1m (LIDAR)

 

Myrddyn Phillips (July 2023)

 

 

 

 

 

Mapping Mountains – Hill Reclassifications – 500m Twmpau

Pt. 511.7m (SH 693 485) – 500m Sub-Twmpau addition

There has been an addition to the listing of the 500m 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. 511.7m (SH 693 485)

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

500m Twmpau - Welsh hills at or above 500m and below 600m in height with 30m minimum drop, with an accompanying sub list entitled the 500m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 500m and below 600m 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 500m Twmpau by Myrddyn Phillips

The hill is being listed by the point (Pt. 511.7m) notation and it is adjoined to the Moelwyn Mawr group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A2), and it is positioned with the A470 road to its east, and has the town of Blaenau Ffestiniog towards the south.

When the list that later became known as the 500m Twmpau was first compiled, this hill was not included in the accompanying sub list due to a basic levelling survey conducted by Myrddyn Phillips on the 13^th July 2004 that resulted in 65ft (19.8m) of drop, and it was subsequently listed with an estimated c 512m summit height and an estimated c 492m bwlch height, with both heights based on interpolation of 10m contouring that appear on the Ordnance Survey 1:25,000 Explorer map. 

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

Since the original compilation of this list 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 mapping resources now available online is the WalkLakes website which hosts an interactive map originated from the Ordnance Survey Open Data programme.  This map has many spot heights not on other publicly available maps and for this hill it has a 512m summit spot height which enabled the numerical detail to be updated, but with 19.8m of drop it was still not included as a 500m Sub-Twmpau. 

Extract from the interactive mapping hosted on the WalkLakes 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 addition of this hill to 500m Sub-Twmpau status is due to LIDAR analysis, resulting in a 511.7m summit height and a 491.7m bwlch height, with these values giving this hill 20.0m of drop, which is sufficient for it to be classified as a 500m Sub-Twmpau. 

 

The full details for the hill are:

Group:  Moelwyn Mawr

Name:  Pt. 511.7m

OS 1:50,000 map:  115

Summit Height:  511.7m (LIDAR) 

Summit Grid Reference:  SH 69325 48552 (LIDAR) 

Bwlch Height:  491.7m (LIDAR) 

Bwlch Grid Reference:  SH 69253 48542 (LIDAR) 

Drop:  20.0m (LIDAR)

 

Myrddyn Phillips (July 2023)