Mapping Mountains – Hill Reclassifications – Humps

 

Werfa (SS 912 947) – Subhump deletion

This is the thirty eighth in a series of Hill Reclassification posts that detail hills whose status has either been altered in the listing of the Humps (HUndred Metre Prominences) through map study, surveys or LIDAR analysis that I have been involved in, or it is the recommendation that their status is altered.

Werfa (SS 912 947) 

Many preceding posts detailing these hill reclassifications are retrospective as they were initiated from studying the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map, or from surveying with the Trimble GeoXH 6000, or from LIDAR analysis, and for this deletion that affected the Humps the email I posted on the Tump Googlegroups forum in relation to this hill was dated 12.11.20.

The listing of Humps was published in book format by Lulu in 2009 and entitled More Relative Hills of Britain, its author; Mark Jackson gives credit to a number of people who contributed toward the formation of this list, these include; Eric Yeaman, Alan Dawson, Clem Clements, Rob Woodall, Bernie Hughes, Pete Ridges and others.  When the list was published in book format there were 2987 Humps listed with their criteria being any British hill that has 100m or more of drop, irrespective of their height.  Accompanying the main list is a sub category entitled Subhumps, with the criteria being any British hill that has 90m or more and below 100m of drop.

More Relative Hills of Britain by Mark Jackson

The details for this deletion appear below:

There has been a deletion to the listing of the Humps (HUndred Metre Prominences) instigated by LIDAR analysis initially conducted by Aled Williams and then independently by Joe Nuttall who produced a summit analysis programme based on heights and drops of hills produced by LIDAR, and as there was a discrepancy in bwlch position for these two studies LIDAR analysis was then conducted by Myrddyn Phillips.

LIDAR bwlch image of Werfa

The bwlch of Werfa

The name the hill is listed by is Werfa and it is adjoined to the Cymoedd group of hills, and it is positioned with the A4190 road to its north-east, and has the village of Abergwynfi towards the north-west.

Prior to this deletion this hill was listed as a Subhump with 90m of drop based on the 568m summit spot height adjoined to a triangulation pillar and which appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps and a bwlch height of c 478m based on interpolation of 10m contouring between 470m – 480m.

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

However, the advent of LIDAR has meant greater accuracy for summit and bwlch heights and their positions.  Currently LIDAR only covers the bwlch of this hill and analysis gives a natural bwlch height of 479.9m positioned at SS 91189 97075.  This re-assessment resulted in a recommendation of this hill being deleted from Subhump status with 88m of drop.

This summit of this hill was subsequently surveyed on the 17.04.21 by Myrddyn Phillips and Aled Williams using a Trimble GeoXH 6000, resulting in a 567.5m summit height and when coupled with the 479.9m bwlch height ascertained from LIDAR analysis, these values give this hill 87.5m of drop.

The Trimble GeoXH 6000 gathering data at the summit of Werfa

The listing of the Humps was updated with the deletion of this hill from Subhump status and this was augmented on the 06.02.21.

 

The full details for the hill are:

Name:  Werfa [Mynydd Llangeinwyr] (as listed in the Humps)

OS 1:50,000 map:  170

OS 1:25,000 map:  166

Summit Height:  568m (as listed in the Humps, with the Trimble GeoXH 6000 survey giving 567.5m)

Summit Grid Reference:  SS 91278 94773 (as listed in the Humps, with the Trimble GeoXH 6000 survey giving SS 91274 94767)

Bwlch Height:  480.0m (as listed in the Humps with independent LIDAR analysis giving 479.9m)

Bwlch Grid Reference:  SS 9118 9707 (as listed in the Humps with independent LIDAR analysis giving SS 91189 97075)

Drop:  88m (as listed in the Humps with the Trimble GeoXH 6000 summit survey and independent LIDAR bwlch analysis giving 87.5m)

 

Myrddyn Phillips (July 2021)