Mapping Mountains – Summit Relocations – Y Pedwarau – The 400m Hills of Wales

Pen Moelallt (SO 003 094)

There has been a Summit Relocation to a hill that is listed in the Y Pedwarau – The 400m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Aled Williams.

LIDAR image of Pen Moelallt (SO 003 094)

The criteria for the list that this summit relocation 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, the list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

The name the hill is listed by is Pen Moelallt and it is adjoined to the Fforest Fawr group of hills, which are situated in the western part of South Wales (Region C, Sub-Region C2), and it is positioned with the A4059 road to its north-west, the A465 road to its south and the A470 road to its north-east, and has the town of Merthyr Tudful towards the south-east.

When the original 400m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the main P30 list with a summit height of c 420m positioned at SO 002 096, with an accompanying note stating; Seven points of same height.  This note refers to the seven 420m ring contours on the summit area of this hill.

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

When the 1^st edition of the Y Pedwarau was published by Europeaklist in May 2013 this hill was listed with c 65m of drop based on an estimated c 423m summit height and a 358m bwlch height, with the latter taken from the spot height on the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map, with the summit grid reference given as SO 001 096 which is a centred position in the largest of the 420m ring contours on the summit area of this hill.

When the Y Pedwarau- The 400m Hills of Wales list was published on Mapping Mountains the summit position for this hill was given as SO 00274 09673, with this taken from the hand-held GPS submissions to DoBIH.

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 Pen Moelallt

The summit height produced by LIDAR analysis is 424.5m at SO 00387 09483, and this position in relation to that previously given comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies to any listed hill whose summit meets the following criteria; where there are a number of potential summit positions within close proximity and the highest point is not where previously given, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist, or when the summit of the hill is in a different field compared to where previously given, or when it is positioned to a different feature such as in a conifer plantation, or when the high point of the hill is placed within a different map contour compared to its previous listed position, or when natural ground or the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary that is judged to be a relatively recent man-made construct.

Therefore, the summit height produced by LIDAR analysis for this hill is 424.5m and is positioned at SO 00387 09483, this position is not given a spot height on contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps and is approximately 200 metres south-eastward from where the previously listed summit is positioned.

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Fforest Fawr

Name:  Pen Moelallt

OS 1:50,000 map:  160

Summit Height:  424.5m (LIDAR)

Summit Grid Reference (new position):  SO 00387 09483 (LIDAR)

  

Bwlch Height:  357.8m (LIDAR)

Bwlch Grid Reference:  SO 00560 07323 (LIDAR)

Drop:  66.7m (LIDAR)

Aled Williams and Myrddyn Phillips (April 2020)