Mapping Mountains – Hill Reclassifications – 200m Twmpau

Erw Penlan (SO 045 495) – 200m Sub-Twmpau addition

There has been a confirmation of an addition to the 200m Twmpau (thirty welsh metre prominences and upward) ranks of hills due to a survey with the Trimble GeoXH 6000, with the survey that confirmed this addition being conducted on the 13^th June 2017.

The criteria for 200m Twmpau status is all Welsh hills at or above 200m and below 300m in height with 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop, and it is the inclusion of this hill in the 200m Sub-Twmpau that has been confirmed. 

The hill did not appear in the original Welsh P30 lists on Geoff Crowder’s v-g.me website as it did not meet the criteria then adopted for the Hills to be surveyed sub list.  The hill was later classified and listed in the sub category after this was standardised and interpolated drop values added, and was included when the updates to the 200m Welsh P30s were published for the Mynydd Epynt group of hills on Mapping Mountains on the 25^th August 2014.  The listing this hill is now a part of is named Twmpau (thirty welsh metre prominences and upward) and its height, drop and status was confirmed by a survey with the Trimble GeoXH 6000.   

Prior to the survey with the Trimble GeoXH 6000 the hill was listed by the name of Coetgae Fawr with an estimated c 21m of drop, based on the 213m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 192m based on interpolation of bwlch contouring between 190m – 200m.

The name that this hill is being listed by is Erw Penlan (see Significant Name Changes) and it is adjoined to the Mynydd Epynt range, which is situated in the south-eastern part of Mid and West Wales (Region B, Sub-Region B2) with its Cardinal Hill being Clepyn Melyn (SN 961 464), and it is positioned above the A 483 road which is to the hill’s north and east, with the town of Llanfair-ym-Muallt (Builth Wells) positioned to its north.

As the hill does not form a part of designated open access land permission to visit should be sought, for those wishing to do so a public footpath connects between minor country lanes to the north and south of the hill’s summit and proceeds around the upper western part of the hill.

The full details for the hill are:

Cardinal Hill:  Clepyn Melyn

Summit Height:  212.1m (converted to OSGM15)

Name:  Erw Penlan

OS 1:50,000 map:  147

Summit Grid Reference:  SO 04597 49535  

Drop:  20.9m (converted to OSGM15)

Erw Penlan (SO 045 495) now confirmed as a 200m Sub-Twmpau addition

For details on the survey that confirmed the addition of this hill to 200m Sub-Twmpau status

Myrddyn Phillips (August 2017)

Mapping Mountains – Hill Reclassifications – 30-99m Twmpau

Pt. 36.9m, Ynys Hir (SH 566 398) – 30-99m Sub-Twmpau addition

There has been an addition to the Twmpau (thirty welsh metre prominences and upward) list with this hill being included in the 30-99m height band.  Accompanying all the 100m height band of hills within the Twmpau are sub lists with the one attached to this list being entitled the 30-99m Sub-Twmpau.

The criteria for 30-99m Twmpau status is all Welsh hills at or above 30m and below 100m in height with 30m minimum drop, whilst the criteria for 30-99m Sub-Twmpau status is all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop.

The details relating to this hill’s addition are retrospective as it was proposed as a possible new P30 by Aled Williams, and subsequently surveyed with the Trimble GeoXH 6000 on the 1^st February 2014.

Prior to the survey with the Trimble this hill was unclassified, with the current Ordnance Survey 1:50,000 Landranger map, 1:25,000 Explorer map and the enlarged mapping hosted on the Geograph website all giving the hill an uppermost 20m ring contour, which implies that the hill does not have sufficient prominence for P30 status but may attain Sub-Twmpau status with 20m or more of drop.

The hill is in the Moel Hebog group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Pt. 734m (SH 525 502) and is situated between the communities of Porthmadog to its south and Tremadog to its north north-west, with the A 487 road to its immediate south.  The hill can be visited from this road where a lay-by gives access through a gate into woodland that covers this and other adjacent small hills.

The name the hill is listed by is Pt. 36.9m, Ynys Hir and as its name implies it forms an island, which is attached to the higher hill known as Ynys Hir (SH 566 396) which is to the immediate south, with both hills now being landlocked, it is included as a 30-99m Sub-Twmpau as the survey with the Trimble GeoXH 6000 produced a summit height of 36.9m (converted to OSGM15) and a bwlch height of 11.1m (converted to OSGM15), with these values giving this hill 25.8m of drop.

The full details for the hill are:

Cardinal Hill:  Pt. 734m (SH 525 502)

Summit Height:  36.9m (converted to OSGM15)

Name:  Pt. 36.9m, Ynys Hir

OS 1:50,000 map:  124

Summit Grid Reference:  SH 56649 39840

Drop:  25.8m (converted to OSGM15)

The Trimble GeoXH 6000 set-up position at the summit of Pt. 36.9m (SH 566 398).  Photo:  Aled Williams

For details on the summit survey and the bwlch survey that confirmed this hill’s 30-99m Sub-Twmpau status

Myrddyn Phillips (July 2017)