Mapping Mountains – Significant Height Revisions – Y Trichant – The 300m Hills of Wales and Y Trechol – The Dominant Hills of Wales

 

Cefn y Coed (SO 211 934) 

There has been a Significant Height Revision to a hill that is listed in the Y Trichant – The 300m Hills of Wales and the Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, the dominance and status of the hill derived from a Leica RX1250 survey conducted by Alan Dawson and a subsequent Trimble GeoXH 6000 summit survey and LIDAR bwlch analysis conducted by Myrddyn Phillips. 

Cefn y Coed (SO 211 934)

The criteria for the two listings that this height revision applies to are:

Y Trichant – The 300m Hills of Wales – Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant, with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13^th May 2017, and the Introduction to the Mapping Mountains publication of the list appearing on the 1^st January 2022. 

Y Trichant - The 300m Hills of Wales by Myrddyn Phillips

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format. 

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Cefn y Coed and this was derived from the Tithe map, the Ordnance Survey One-Inch ‘Old Series’ map and local enquiry, and it is adjoined to the Cilfaesty group of hills, which are situated in the north-eastern part of South Wales (Region B, Sub-Region B2), and it is positioned with a minor road to its north and the A489 road to its south, and has the town of Trefaldwyn (Montgomery) to its north north-east.

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was listed with a non interpolated summit height of c 355m, based on the uppermost ring contour that appears on the Ordnance Survey 1:25,000 Explorer map. 

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with an estimated c 173m drop, based on an estimated c 356m summit height and an estimated c 183m bwlch height, with both heights based on interpolation of 5m contouring that appears on the Ordnance Survey 1:25,000 Explorer map. 

The Leica RX1250 set-up position at the summit of Cefn y Coed

However, it was not until the survey with the Leica RX1250 and subsequent LIDAR analysis and the survey with the Trimble GeoXH 6000 that the details for this hill could be accurately re-assessed. 

The Trimble GeoXH 6000 gathering data at the summit of Cefn y Coed

The summit height produced by the Leica RX1250 survey is 353.5m positioned at SO 21163 93413 and the summit height produced by the Trimble GeoXH 6000 survey is 353.6m positioned at SO 21164 93411, and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey, Harvey or other interactive map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR.  Also included are hills whose summit map data is missing an uppermost ring contour when compared with the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 353.6m and this was derived from a Trimble GeoXH 6000 survey, this is 2.4m lower than the previously listed summit height of c 356m, which was based on interpolation of the uppermost ring contour that appears on the contemporary Ordnance Survey 1:25,000 Explorer map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Cilfaesty

Name:  Cefn y Coed

OS 1:50,000 map:  137

Summit Height (New Height):  353.6m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SO 21164 93411 (Trimble GeoXH 6000)  

Bwlch Height:  184.2m (LIDAR)

Bwlch Grid Reference:  SO 20667 90868 (LIDAR)

Drop:  169.3m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  47.89% (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

Myrddyn Phillips (May 2026)