Tuesday 11 December 2018

Mapping Mountains – Trimble Surveys – Yr Eifl


10.09.18  Bryn (SH 426 361)  

Today I wanted to visit a hill that Chris Pearson had proposed as a new Tump in February of this year, and which Chris Crocker then LIDARed as having 30.2m of drop, with a 36.9m summit and 6.7m bwlch height.  The hill is now listed as Penychain in the Tumps, and was first listed in the sub list that accompanied the 30-99m Welsh P30 list on Geoff Crowder’s v-g.me website under the invented name of Creigiau Penychain.

LIDAR summit image of Bryn

Prior to my visit I also LIDARed the hill and analysed its summit and bwlch contours, concluding that the hill is not a natural P30 as LIDAR bwlch contouring implies that the natural bwlch would once have been over 7m in height.  This bwlch is now reduced in height due to a railway cutting. 

LIDAR image of Bryn showing the railway cutting toward the top right of the image

I also researched an appropriate name for the hill via the Tithe map, and found that the upper section of the hill which now comprises one field, used to comprise two, with the boundary between each showing as a slight elevation on LIDAR.  This boundary although old, is not ancient, and would be a man-made construction.  LIDAR also shows that the natural summit of this hill still exists, close to the old field boundary.  Therefore I wanted to take data sets from the slightly raised field boundary, and the natural summit with LIDAR giving two potential positions for this, with one adjacent to the old field boundary and the other a few metres distant from it.  I had considered surveying the bwlch, but as its critical point is positioned behind a chalet in a holiday park I thought my intrusion may not be welcome, therefore the three planned surveys at this hill’s summit would have to suffice.

For those wishing to visit this hill there is parking for two cars beside the entrance to the Penychain Railway Station, from here a rough road proceeds toward the farm of Penychain.

As I left my car I looked over the railway bridge toward where the bwlch is situated, the rail line curved leftward out of view, with the bwlch to the right and on the other side of the perimeter fence, I thought it wise not to visit this bwlch and the height produced via LIDAR analysis would be sufficient when coupled with an on-site visit and the three planned Trimble surveys to confirm (or otherwise) this hill’s reclassification to the P30 Twmpau and Dominant ranks.

The railway that now cuts through the natural bwlch of this hill

The rough road led up toward the farm, one vehicle was parked outside when I approached, I did contemplate knocking on the door to make place-name enquiries with the farmer to check on this hill’s locally known name, but decided this was best to do after visiting its summit.

There is only one detailed log of this hill on the Hill Bagging website and that is by Alex Cameron who suggests that following the track to the right after passing the farm house avoids the worst of the gorse which swamps the majority of this hill, I was thankful for Alex’s advice as otherwise I may have ventured further on the track following the public right of way and tried a gorse bash that no doubt would have proved unwelcome.

The track on the southern side of the farm house leads to a gate, and just on the left of this is rough grass and an ATV track that leads through more rough grass toward the summit of the hill.

The view from the top is extensive and I stood and stared for a number of minutes following the coast as it swung south-westward toward Ynys Enlli, to the north-east the higher Eryri peaks were on display, some blanketed in the morning’s cloud, but many were free of murk with their greyed silhouettes merging from one to another.

Finding the high point of the slightly raised old field boundary was easy and when doing so I checked the ten figure grid reference produced via LIDAR against that showing on the screen of the Trimble.  This point consists of rough grass and as I set the Trimble up I stood looking north-east following the course of the old boundary across the summit area of the hill, this soon disappeared as it was swallowed by gorse bushes, turning round I again followed the old boundary’s course, this time south toward steepening slopes as it plunges down to a connecting field boundary, again this soon disappears in to gorse on the area of the summit, but the old field boundary is easily picked out and this would no doubt be man-made.

Gathering data at the high point of the old field boundary

Once Trimble data were gathered and stored I next surveyed the point where LIDAR gives the remaining natural summit of the hill to be positioned, this is no more than 4 metres from the high point of the boundary, I wondered if at one time it may have been a part of it, but LIDAR dismisses this and I concluded that it was not a part of the old boundary and is still a natural part of the hill.  As the Trimble beeped away gathering data I stood back and admired the view, for such a small heighted hill this proved wonderful and to be here all alone with the breeze blowing inland from the near sea was a sheer pleasure.  I then collected a second data set from this second point, and once stored moved on to where LIDAR gives another potential natural summit to be situated.

The position of the second data set with the old field boundary in the background

This third point consists of rock and I wondered if LIDAR had bi-passed its highest point, and as the Trimble gathered its allotted data I again stood back and savoured the view.  Once data were stored, all that remained was to retrace my inward route back down the hill to my car.

Gathering data at where the Trimble identified as the natural summit of Bryn

As I neared the gate adjacent to Penychain farm a vehicle appeared coming up the road, it was the local farmer, my timing could not have been better.  After introducing myself and explaining my interest in his hill and its name we talked for 15 minutes or so, he proved extremely knowledgeable and asked me not to mention him by name, as he wanted this to remain private.

He explained that the hill is known as the Bryn, without the use of the definite article ‘Y’, and as is the want of generic names it is also referred to locally as Bryn Penychain to differentiate it from other hills named Bryn in the local area.  I asked what of these two names would he prioritise and he said; Bryn.

I then told him about the Tithe names given to the two fields which are now one on the upper part of the hill, with the north-westerly field where the natural summit of the hill is situated being named Bryn Cefn Tŷ, and the south-easterly field named Cae Bryn on the Tithe.  He confirmed that the field used to be split in two and told me where the boundary went from his farm to the upper part of the hill and over its top down to another field boundary, which matches the course shown on the Tithe map, he then started giving me field names on the other side of the hill as well as one on the other side of the gate directly up the track from where we were standing.

I find it interesting that the two fields at the time of the Tithe both reference the word Bryn in their name, and this generic word is also the name that the local farmer knows the hill as.

Thanking him for his time I wandered back down the rough road toward my car, it had been a good morning on the hill taking four data sets, having an inspection of the old field boundary and then meeting the local farmer who confirmed the name of this hill.



Survey Result:



Summit Height:  36.7m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 42656 36173 (Trimble GeoXH 6000) (summit relocation confirmed)

Bwlch Height:  6.6m (LIDAR)

Bwlch Grid Reference:  SH 43103 36535 (LIDAR)

Drop:  30.0m (Trimble GeoXH 6000 summit and LIDAR bwlch) (30-99m Sub-Twmpau reclassified to 30-99m Twmpau)

Dominance:  81.88% (Trimble GeoXH 6000 summit and LIDAR bwlch) (Dominant addition confirmed)








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