Mapping Mountains – Significant Name Changes – The Welsh P15s

Mynydd Trallwng (SN 965 311) 

There has been a Significant Name Change to a hill that is listed in The Welsh P15s, 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 Mynydd Trallwng (SN 965 311)

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

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s 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 minor roads to its north-east and south, and the A40 road farther to its south, and has the village of Pontsenni (Sennybridge) towards the west south-west.

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the 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 point (Pt. 377m) notation with 2om of drop (therefore listed as a Sub-Trichant with subsequent LIDAR analysis giving it 19.6m of drop), based on the 377m summit spot height that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and the 357m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

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

Since the original publication of the Welsh P30 lists on Geoff Crowder’s v-g.me website 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 historic maps now available online is the Ordnance Survey Draft Surveyors map which formed the basis for the first publicly available Ordnance Survey One-Inch ‘Old Series’ map, and it is the Draft Surveyors map that has prompted the change in the listed name of this hill. 

Extract from the Ordnance Survey Draft Surveyors Map

The Draft Surveyors maps consist of the preliminary drawings made by the Ordnance Survey surveyors between the 1780s and 1840 and formed the basis for the first publicly available One-Inch map.  They were drawn at scales of six inches to the mile for areas considered of particular military significance and down to two inches to the mile for other areas.  Fair copies were then produced from these preliminary drawings to one inch to the mile and then copper plates were prepared for printing.  The Draft Surveyors maps for the whole of Wales are now available online and they form an important part in the study of Welsh upland place-names as they bridge the time frame between the late 18^th century and the mid-19^th century when the Ordnance Survey produced their first One-Inch maps, and importantly for this hill and its listed name, it is this map that places the name Mynydd Trallwng adjacent to the summit of this hill.

Therefore, the name this hill is now listed by in the The Welsh P15s is Mynydd Trallwng, and this was derived from the Ordnance Survey Draft Surveyors Map. 

 

The full details for the hill are: 

Group:  Mynydd Epynt 

Name:  Mynydd Trallwng

Previously Listed Name:  Pt. 377m 

OS 1:50,000 map:  160

Summit Height:  376.9m (LIDAR)                                                           

Summit Grid Reference:  SN 96522 31151 (LIDAR) 

Bwlch Height:  357.3m (LIDAR) 

Bwlch Grid Reference:  SN 96272 31300 & SN 96275 31303 (LIDAR) 

Drop:  19.6m (LIDAR) 

 

Myrddyn Phillips (May 2025) 

Mapping Mountains – Hill Reclassifications – Y Trichant – The 300m Hills of Wales

Mynydd Trallwng (SN 965 311) – Sub-Trichant deletion

There has been a deletion from the list of Y Trichant – The 300m 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 Myrddyn Phillips. 

LIDAR image of Mynydd Trallwng (SN 965 311)

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

Y Trichant – The 300m Hills of Wales – Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant, with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13^th May 2017, and the Introduction to the Mapping Mountains publication of the list appearing on the 1^st January 2022. 

Y Trichant - The 300m Hills of Wales by Myrddyn Phillips

The name the hill is now listed by is Mynydd Trallwng and this was derived from the Ordnance Survey Draft Surveyors map, 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 minor roads to its north-east and south, and the A40 road farther to its south, and has the village of Pontsenni (Sennybridge) towards the west south-west.

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the 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 2om of drop, based on the 377m summit spot height that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and the 357m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

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 deletion of this hill from Sub-Trichant status is due to LIDAR analysis, resulting in a 376.9m summit height and a 357.3m bwlch height, with these values giving this hill 19.6m of drop, which is insufficient for it to be classified as a Sub-Trichant. 

 

The full details for the hill are: 

Group:  Mynydd Epynt 

Name:  Mynydd Trallwng 

OS 1:50,000 map:  160

Summit Height:  376.9m (LIDAR)                                                           

Summit Grid Reference:  SN 96522 31151 (LIDAR) 

Bwlch Height:  357.3m (LIDAR) 

Bwlch Grid Reference:  SN 96272 31300 & SN 96275 31303 (LIDAR) 

Drop:  19.6m (LIDAR) 

 

Myrddyn Phillips (June 2024)