Mapping Mountains – Summit Relocations – 500m Twmpau and Welsh Highlands – Uchafion Cymru

Foel Fawr (SH 728 392)

There has been a Summit Relocation to a hill that is listed in the 500m Twmpau and the Welsh Highlands – Uchafion Cymru, 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 Aled Williams on the 19^th July 2020.

Foel Fawr (SH 728 392)

The criteria for the two listings that this summit relocation applies to are:

500m Twmpau – Welsh hills at or above 500m and below 600m in height that have 30m minimum drop, with an accompanying sub category entitled the 500m Sub-Twmpau consisting of all Welsh hills at or above 500m and below 600m in height that have 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 published on Mapping Mountains in Google Doc format.

The 500m Twmpau by Myrddyn Phillips

Welsh Highlands – Uchafion Cymru – This is the revised draft title for the Welsh 500m P15s list that takes in all hills in Wales at or above 500m in height with 15m minimum drop.  The list is co-authored by Myrddyn Phillips and Aled Williams with the Introduction to the list being published on Mapping Mountains in November 2015 and an update relating to the list appearing on Mapping Mountains on the 19th June 2019.

The Welsh Highlands - Uchafion Cymru by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Foel Fawr and it is adjoined to the Arenig Fach 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 B4391 road to its north, the A470 road to its west and the A4212 road to its south, and has the village of Trawsfynydd towards the south-west.

When the original list of Welsh 500m P15s that later became known as Yr Uchafion and latterly as The Welsh Highlands – Uchafion Cymru was first compiled, this hill was listed with an estimated c 41m of drop based on the 528m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and which is positioned at SH 72620 39472, and an estimated c 487m bwlch height, based on interpolation of 10m contouring between 480m - 490m.

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

Since first compilation of the Welsh 500m P15 list there have been a number of Ordnance Survey 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 are current and 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, and it was this map that showed a 528m map heighted twin summit positioned at SH 72873 39268.  The two 528m spot heights are also shown on the mapping hosted on the Magic Maps website.

Extract from the Magic Maps website

However, it was not until the survey with the Trimble GeoXH 6000 that the details for this hill could be accurately re-assessed.  The height and position for each summit is given below:

South-easterly summit:  528.611m at SH 72872 39284

North-westerly summit:  527.542m at SH 72621 39476

The above detail compared to the prioritised summit previously given comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour either on Ordnance Survey maps or interactive mapping, to a different point where a number of potential summit positions are within close proximity, 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 or covered reservoir that is considered a relatively recent man-made construct, or the listing of a new twin summit or de-twinning of a summit, 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.

Gathering data at the higher of the Foel Fawr summits

Gathering data at the lower of the Foel Fawr summits

Therefore, the summit height produced by the Trimble GeoXH 6000 survey is 528.6m and this is positioned at SH 72872 39284, this position is not given a spot height on contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps, but is given a 528m spot height on the interactive mapping hosted on the Magic Maps website, and is approximately 260 metres south-eastward from where the previously listed and prioritised summit is positioned.

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Arenig Fach

Name:  Foel Fawr

OS 1:50,000 map:  124

Summit Height:  528.6m (converted to OSGM15)

Summit Grid Reference (New Position):  SH 72872 39284

  

Bwlch Height:  485.5m (converted to OSGM15)

Bwlch Grid Reference:  SH 73074 39525

Drop:  43.1m

Myrddyn Phillips and Aled Williams (October 2020)