Mapping Mountains - Hill Reclassifications - Y Pedwarau - The 400m Hills of Wales

 

Y Pedwarau – Hill Reclassifications

Y Pedwarau are the Welsh hills at or above 400m and below 500m in height that have a minimum drop of 30m.  Accompanying the main P30 list are five sub lists; these are the 500m Sub-Pedwar, 500m Double Sub-Pedwar, 400m Sub-Pedwar, 390m Sub-Pedwar and 390m Double Sub-Pedwar category’s, with their criteria detailed in the respective Change Registers that have been created and which are linked in their above titles, with the Introduction to this list being linked in the above title.

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

Mapping Mountains - Hill Reclassifications - Y Pedwarau

Esgair Saeson (SN 795 603) – 400m Sub-Pedwar addition (107th reclassification)

There has been an addition to the listing of the Y Pedwarau – The 400m 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 Aled Williams. 

LIDAR image of Esgair Saeson (SN 795 603)

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

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are five categories of sub hills, with this hill being included in the 400m Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

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.

When the original 400m height band of Welsh P30 hills was published on Geoff Crowder’s v-g.me website, this hill was not included in the Hills to be surveyed sub list, as with a 500m summit spot height that appears on the contemporary Ordnance survey 1:50,000 Landranger and 1:25,000 Explorer map, its height was above the criterion used for this list.

With a summit spot height of 500m this hill was subsequently listed in the 500m Twmpau, and 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 inclusion of this hill as a 400m Sub-Pedwar 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 sufficient for it to be classified as a 400m Sub-Pedwar.

                                     

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) 

 

For the additions, reclassifications and deletions to Y Pedwarau – The 400m Hills of Wales reported on Mapping Mountains since the May 2013 publication of the list by Europeaklist please consult the following Change Registers:

 

Y Pedwarau

 

Y Pedwarau – 400m Sub-Pedwarau

 

Y Pedwarau – 390m Sub-Pedwarau

 

Y Pedwarau – 390m Double Sub-Pedwarau

 

Myrddyn Phillips and Aled Williams (November 2023)

Mapping Mountains - Hill Reclassifications - Y Pedwarau

Pen y Bwlch Coch (SH 751 159) – 390m Double Sub-Pedwar reclassified to 390m Sub-Pedwar (106th reclassification)

There has been a reclassification to the listing of the Y Pedwarau – The 400m Hills of Wales, 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 Pen y Bwlch Coch (SH 751 159)

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

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main Y Pedwarau list are five categories of sub hills, with this hill being reclassified from the 390m Double Sub-Pedwar category to the 390m Sub-Pedwar category.  The criteria for the former being all Welsh hills at or above 390m and below 400m in height that have 20m or more and below 30m of drop, with the criteria for the latter being all Welsh hills at or above 390m and below 400m in height that have 30m minimum drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Pen y Bwlch Coch, and it is adjoined to the Cadair Idris group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and it is positioned with the A470 road to its north and the A487 road to its east, and has the town of Dolgellau towards the north-west.

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 Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 category. 

Extract from 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 26m of drop, based on the 395m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger map and the 369m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website which was entitled the Interactive Coverage Map, however it was noted that the latter spot height was not centralised where interpolation would place the critical point of the bwlch, and these were the values this hill was listed by when the 1^st edition of the Y Pedwarau was published by Europeaklist in May 2013. 

Extract from the Ordnance Survey 1:50,000 Landranger 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 bwlch contouring between 365m – 370m, with interpolation placing the height of the bwlch as an estimated c 366m, and when coupled with the 395m summit spot height these values gave this hill an estimated c 29m 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.

Therefore, the reclassification of this hill from 390m Double Sub-Pedwar status is due to LIDAR analysis, resulting in a 395.1m summit height and a 364.9m bwlch height, with these values giving this hill 30.2m of drop, which is sufficient for it to be classified as a 390m Sub-Pedwar. 

 

The full details for the hill are:

Group:  Cadair Idris 

Name:  Pen y Bwlch Coch 

OS 1:50,000 map:  124

Summit Height:  395.1m (LIDAR)                                                           

Summit Grid Reference:  SH 75190 15937 (LIDAR) 

Bwlch Height:  364.9m (LIDAR) 

Bwlch Grid Reference:  SH 75107 15780 (LIDAR) 

Drop:  30.2m (LIDAR) 

 

For the additions, reclassifications and deletions to Y Pedwarau – The 400m Hills of Wales reported on Mapping Mountains since the May 2013 publication of the list by Europeaklist please consult the following Change Registers:

 

Y Pedwarau

 

Y Pedwarau – 400m Sub-Pedwarau

 

Y Pedwarau – 390m Sub-Pedwarau

 

Y Pedwarau – 390m Double Sub-Pedwarau

 

Myrddyn Phillips and Aled Williams (September 2023)