Monday, 30 May 2016

Mapping Mountains – Summit Relocations – 100m Twmpau

Pt. 173.8m (SN 225 503)

There has been a Summit Relocation to the 100m Twmpau (thirty welsh metre prominences and upward) list initiated by a survey with the Trimble GeoXH 6000, with the survey that resulted in this summit relocation being conducted on the 13th May 2016.

The hill is adjoined to the Rhos Ymryson range of hills and is situated to the north-east of Aberteifi (Cardigan) and to the west south-west of Aberporth, with the high point of the hill being close to the small community of Felinwynt which only comprises a few houses, and as the hill does not possess a name of its own on current Ordnance Survey maps, and as I do not know an appropriate name for it either from local enquiry or from historical research it is being listed under the point (Pt. 173.8m) notation.

Access to the hill is relatively easy as it comprises a large grassy field which has a minor lane running over it in a north to south direction.  However, the high point as surveyed with the Trimble GeoXH 6000 is not on open access land and therefore permission to visit should be sought.

The highest spot height adjoined to this hill on Ordnance Survey maps is 174m and this is positioned on the minor lane and adjacent to where a fence heads westward across a field.  A data set was taken with the Trimble from the high point of the road as well as from what was deemed to be the high point of the adjacent field, the results appear below:

High point of road:  173.7m (173.695m, converted to OSGM15)

High point of field:  173.8m (173.811m, converted to OSGM15)

These two results are very close and there is a possibility that higher ground exists in the field when compared to where the Trimble set-up position was placed.  However, for now this Trimble data is the most accurate that is known for this hill, and although the corner of the field is very close to the high point of the road it is worth itemising this positional change as a summit relocation as many people may just dip their toe on the tarmac instead of visiting the land within the adjacent field.

Therefore, the known higher part of the hill as surveyed with the Trimble GeoXH 6000  is not on the minor lane as ground in the adjacent westerly field is approximately 0.12m higher.

The full details for the hill are:

Cardinal Hill:  Rhos Ymryson

Summit Height:  173.8m (converted to OSGM15)

Name:  Pt. 173.8m

OS 1:50,000 map:  145

Summit Grid Reference (New Position):  SN 22587 50306 
Drop:  c 55m

The Trimble GeoXH 6000 gathering data at the summit of Pt. 173.8m, with the minor road where the 174m spot height appears on the ground on the other side of the gorse hedgerow in the background of this photograph

For details on the survey that relocated the summit of this hill.

Myrddyn Phillips (May 2016)

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