Mapping Mountains – Summit Relocations – Y Pedwarau

Llandegle Rocks (SO 132 617)

There has been a Summit Relocation to a hill listed in the Y Pedwarau which was initiated by LIDAR data analysed by Aled Williams and confirmed by a survey with the Trimble GeoXH 6000, with the survey that resulted in this summit relocation taking place on the 3^rd October 2017 in good, clear conditions.

The list that this summit relocation affects is:

Y Pedwarau – All Welsh hills at and above 400m and below 500m in height that have a minimum 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and the Introduction to the Mapping Mountains publication of the list appeared on the 30^th January 2017. 

The name of the hill is Llandegle Rocks and it is situated in the Fforest Glud range, this group of hills is positioned in the eastern part of Mid and West Wales (Region B, Sub-Region B1), and the hill is situated with the small community of Llandegle to the north north-east and Pen-y-bont to the north-west.  The upper part of the hill is made up of an island of designated open access land, with public footpaths leading to it from the west, north, east and south.  

Llandegle Rocks (SO 132 617)

The hill’s summit position was previously given as SO 131 618, this is where the 436m spot height appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps, which is adjoined to a triangulation pillar with the flush bracket height of 436.473m.  Ordnance Survey maps also give a separate 430m ring contour towards the south-east that is not spot heighted and which visually is close in height to where the summit was listed. 

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

However, prior to the survey with the Trimble GeoXH 6000 this hill’s summit was analysed using LIDAR data by Aled Williams.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

 

Aled’s analysis of LIDAR data gives the hill the following details:

Llandegle Rocks (contour ring with trig pillar)

Summit Height:  436.1m

Summit Grid Reference:  SO 13145 61803

Llandegle Rocks (south-east 430m ring contour)

Summit Height:  436.3m

Summit Grid Reference:  SO 13202 61751

Bwlch Height:  345.5m

Bwlch Grid Reference:  SO 11362 59618

Drop:  90.8m

Whilst the height produced by the Trimble GeoXH 6000 appears below:

Llandegle Rocks (contour ring with trig pillar)

Summit Height:  436.258m (converted to OSGM15)

Summit Grid Reference:  SO 13145 61803

Llandegle Rocks (south-east 430m ring contour)

Summit Height:  436.344m (converted to OSGM15)

Summit Grid Reference:  SO 13202 61752

The Trimble GeoXH 6000 gathering data at the old summit position of Llandegle Rocks with the new position for the summit on the left of this photo

Therefore, the position of the relocated summit is at SO 13202 61752 and is featureless ground consisting of grass, this position is within the south-eastern 430m ring contour on Ordnance Survey maps, although no spot height is given to it, the relocated summit is approximately 70 metres south-eastward from where the previously listed summit is positioned.

The full details for the hill are:

Cardinal Hill:  Gilwern Hill

Summit Height:  436.3m (converted to OSGM15)

Name:  Llandegle Rocks

OS 1:50,000 map:  148

Summit Grid Reference (New Position):  SO 13202 61752  

   

Drop:  90.8m

The Trimble GeoXH 6000 gathering data at the new summit position of Llandegle Rocks with the old summit position beside the trig pillar in the background of this photo

For details on the survey that confirmed the summit relocation of this hill

Myrddyn Phillips and Aled Williams (December 2017)