Mapping Mountains – Hill Reclassifications – Y Pedwarau – The 400m Hills of Wales

Lan Fawr (SN 692 501) – Pedwar reclassified to 400m Sub-Pedwar

There has been a reclassification to the listing of the Y Pedwarau – The 400m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Trimble GeoXH 6000 survey conducted on the 5^th January 2020 by Myrddyn Phillips with assistance from Rob Woodall, with subsequent LIDAR bwlch analysis prioritised.

Lan Fawr (SN 692 501)

The criteria for the list that this reclassification 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, accompanying the main list are five categories of sub hills, with this hill being reclassified to the 400m Sub-Pedwar category.  The criteria for 400m Sub-Pedwar status being all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Lan Fawr, and it is adjoined to the Esgair Wen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with the Afon Teifi and the B4343 road to its north-west and the A482 road to its south-west, and has the village of Llanbedr Pont Steffan (Lampeter) towards the west.

When the 1^st edition of the Y Pedwarau was published by Europeaklist in May 2013, this hill was listed as a 400m Sub-Pedwar with 28m of drop, based on the 429m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and the 401m 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 and which is positioned at SN 69498 50464.  This spot height is also shown on Ordnance Survey data that appears on the Magic Maps website. 

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

The details for this hill were re-assessed when the OS Maps website became available online.  This is the replacement for OS Get-a-map and has contours at 5m intervals which are proving consistently more accurate compared to the 5m contours that sometimes appear on the Ordnance Survey 1:25,000 Explorer map and used to appear on the online Vector Map Local.  This re-assessment resulted in the hill being listed with an estimated c 30m of drop, based on interpolation of 5m bwlch contouring between 395m – 400m.

The Trimble GeoXH 6000 gathering data at the summit of Lan Fawr

The 401m spot height that appears on the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map originates from a 1316ft (401.1m) imperial height that appears on the Ordnance Survey series of Six-Inch maps.  This seems to be a levelled height and was not necessarily taken to the critical point of this bwlch.  As a consequence of these re-assessments this hill was reclassified to a Pedwar with an estimated c 30m of drop.

The Trimble GeoXH 6000 gathering data on the bwlch area of Lan Fawr

However, it was not until The Trimble GeoXH 6000 survey and subsequent LIDAR analysis 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 image of Lan Fawr (SN 692 501)

Therefore, the reclassification of this hill to 400m Sub-Pedwar status is due to a Trimble GeoXH 6000 survey and subsequent LIDAR analysis, resulting in a 427.4m summit height and a 398.2m bwlch height, with these values giving this hill 29.2m of drop which is insufficient for it to be classified as a Pedwar.

The full details for the hill are:

Group:  Esgair Wen

 

Name:  Lan Fawr

OS 1:50,000 map:  146

Summit Height:  427.4m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SN 69244 50156 (Trimble GeoXH 6000)

Bwlch Height:  398.2m (LIDAR)

Bwlch Grid Reference:  SN 69489 50456 (LIDAR)

Drop:  29.2m (Trimble GeoXH 6000 summit and LIDAR bwlch)

For the additions, reclassifications and deletions to Y Pedwarau – The 400m Hills of Wales reported on Mapping Mountains since the May 2013 publication of the list by Europeaklist please consult the following Change Registers:

Y Pedwarau

Y Pedwarau – 400m Sub-Pedwarau

Y Pedwarau – 390m Sub-Pedwarau

Y Pedwarau – 390m Double Sub-Pedwarau

Myrddyn Phillips and Aled Williams (May 2020)