Mapping Mountains – Trimble Surveys – Mynydd Hiraethog

18.09.19  Bryn Trillyn (SH 947 590, only bwlch surveyed)

The connecting bwlch of Bryn Trillyn is in utter contrast to its summit.  The latter is heather bound with moor grass and extensive views toward the higher Eryri hills, whilst its bwlch is in a field next to the A543 road at it speeds its way from the outskirts of Pentrefoelas toward Dinbych (Denbigh) in the north-east.

The summit of Bryn Trillyn (SH 947 590)

I’d last visited its summit along with Mark Trengove; watching the sunset from its high point as a thin flash of yellowed light highlighted an otherwise deep and darkening blued sky.

Weather and time of day can dictate many aspects of hill walking, and especially for those related to emotive state, and where the summit had been otherworldly with purpled heather and stillness of the setting sun, my visit to the bwlch consisted of greened fields and an occasional passing vehicle, with middays warmth leaving a contented feeling, but one mainly based on a good job done, as I needed to gather two sets of data, one from either side of the road where the hill to hill traverse descended to a slightly raised strip of tarmac, leaving a low point in each opposing field.

I’d examined the lay of land of this bwlch via the digitised image in a Google car and found a convenient parking place and realised before visiting that a point in the field either side of the road would need surveying.  Therefore, as I left my car I had a quick look on both sides of the road and decided that as the digitised image suggested; two data sets were required.

The Trimble was soon set-up atop my rucksack gathering data on the eastern side of the road.  Its placement was relatively easy to pinpoint as a greened and grassed small and broad ridge descended to the boundary fence, and once data were gathered and stored I closed the equipment down and headed back to the road and the field on its other side.

Gathering data at the bwlch area of Bryn Trillyn

The point to survey on the western side of the road was much tighter and in a dip close to the boundary fence, and as the Trimble beeped away collecting its individual datum points I happily stood back in the sunshine content that this third bwlch survey of the day was nearing completion, but with another six planned I could not linger. 

Gathering data at the second option for the bwlch of Bryn Trillyn

So, once the allotted data were gathered and stored I packed the equipment away and headed back the short distance to my car, checked the map and continued north-east toward the bwlch of Moel Fechan.

LIDAR bwlch image of Bryn Trillyn

Postscript:

Since surveying this hill full LIDAR coverage is now available.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height and positional data that is now freely available for England and Wales.  Consequently the numerical details for this hill have been analysed using this technique, and where appropriate LIDAR has been used in preference to that produced by the Trimble. 

Survey Result:

Bryn Trillyn

Summit Height:  495.6m (LIDAR)

Summit Grid Reference:  SH 94754 59091 (LIDAR) (summit relocation)

Bwlch Height:  446.6m (LIDAR)

Bwlch Grid Reference:  SH 96285 59660 (LIDAR)

Drop:  49.0m (LIDAR)

Dominance:  9.88% (LIDAR)

  

For details on the summit survey of Bryn Trillyn

For further details please consult the Trimble Survey Spreadsheet

Mapping Mountains – Trimble Surveys – Mynydd Hiraethog

22.08.14  Bryn Trillyn (SH 947 590)

Bryn Trillyn (SH 947 590)

Bryn Trillyn is positioned on the western fringe of Mynydd Hiraethog and looks out on desolation of moor.  It is easily accessible from the A543 which is just to its south-east.  The hill forms part of an extensive upland between the Welsh coast to the north, the Afon Conwy to the west, the hills of the Arennig to the south and the Afon Clwyd to the east.

This was my fourth and last walk of the day, and the second with Mark.  We’d just had a magical illuminated hour in the company of Moel Tywysog (SH 984 657) and confirmed its Pedwar status with a Trimble survey, we now wanted to watch the sun disappear behind the higher Eryri peaks and collect data to see if this 496m map heighted hill could become a fully-fledged Dewey.

We parked in a lay-by a few hundred metres south of the Sportsman’s Arms (SH 952 590).  This house is now for sale, it was once reputed to be the highest Inn in Wales, but the beer stopped being served a number of years ago.

We walked back up the road toward the Sportsman’s Arms and headed west over a foot stile on to a track, this leads to the summit of Bryn Trillyn, we diverged from the track and followed a fence line toward the heather moor.  Bearing left at the next fence junction directed us straight for the summit with reclaimed sheep pasture on the southern side of the fence and heather on the northern.  Mark chose the latter and I the former to walk on.  The heather was ablaze with delicate purples, all colour slightly diffused as the sun sank behind a thickening grey sky to the west.

Heading for the summit of Bryn Trillyn

We were now walking on a raised heather embankment which led straight to the high point of the hill, with subsequent research giving it as an old parish boundary.  After we reached the summit Mark went off to investigate the ruin of Gwylfa Hiraethog, whilst I set the Trimble up on its improvised tripod on the high point of the embankment.  Mark and I discussed the merits of including this as a part of the hill, which it could be considered a part of as nature had now taken it over, but it was obviously mad-made and because of this it was eventually discounted as the high point of the hill.

Mark approaching the high point of Bryn Trillyn

As the Trimble attained its 0.1m accuracy and data were collected I looked up and Mark was standing in the centre of the ruin, much higher than my position as the rubble of the old house had been in situ long enough for it to be stabilised and for grass to grow on it, however we both agreed that this was definitely man-made.

The ruined Gwylfa Hiraethog

The subtle grey of the northern Carneddau

Gathering data at the first of three positions

Gwylfa Hiraethog was once a shooting lodge of Hudson Ewbanke Kearley; the first Viscount Devonport, whose main estate was Wittington House in Buckinghamshire.  Its origins date to the early 1890’s when a wooden chalet was erected; this was transported from Norway in prefabricated sections.  The chalet was later incorporated in to a larger stone built lodge, this was later enlarged in 1913 under the guidance of the architect Sir Edwin Cooper, photographs show the lodge as an imposing mansion in the Jacobean style, with a three gabled front with cross wings, long windows and a stone flagged floor.

Gwylfa Hiraethog was once an impressive house which was used as a shooting lodge

The Gwylfa Hiraethog estate was put up for sale by Viscount Devonport in 1925, it was then described as a shooting box with residence comprising 11 principal bedrooms, two secondary bedrooms and servant’s quarters.  Following the sale the lodge became the residence of the estate gamekeepers and was finally abandoned in the 1960’s.  Its subsequent deterioration has been rapid and it now stands as a ruin.

By now the thickening mass of grey cloud to the west was shielding the sun with only a flicker of piercing orange tailing out to the north, as the black outline of hills mirrored the deep blue of the sky.  This only lasted a few minutes as the blaze of sun disappeared from view, supplanted by twilight’s darkening.

The sun piercing the cloud and tailing out to the north

I definitely wanted to discover a new Dewey and with a smile on my face insisted that the rubble strewn inner part of the abandoned old shooting lodge could definitely constitute the summit of a hill!  Therefore five minutes of data were collected from inside the house atop the grassed rubble.

Gathering data at the second of three positions

During this Mark investigated the moor and found a point that looked to be the highest outside of the heather embankment, once the Trimble had gathered its five minutes of allotted data from the top of the rubble summit I headed toward Mark.

Mark stands at the point for the third survey with his walking pole at the high point of the embankment and the highest remaining natural ground indicated by LIDAR at the base of the embankment on the right of the photo

In darkening conditions the Trimble was placed on its improvised tripod at the point Mark had found.  By now photography without the aid of using a flash resulted in a blurred image, once data were stored we headed down the grassed track back to the Sportsman’s Arms and the awaiting car.  Three points surveyed and my vote definitely goes toward the rubble summit!

Tryfan in centre background

Gathering data at the last of three positions

Postscript:

Since surveying these hills full LIDAR coverage is now available.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height and positional data that is now freely available for England and Wales.  Consequently the numerical details for these hills have been analysed using this technique, and where appropriate LIDAR has been used in preference to that produced by the Trimble.

LIDAR summit image of Bryn Trillyn

Survey Result:

Bryn Trillyn

Summit Height:  495.6m (LIDAR)  

Summit Grid Reference:  SH 94754 59091 (LIDAR) (summit relocation)

Bwlch Height:  446.6m (LIDAR)

Bwlch Grid Reference:  SH 96285 59660 (LIDAR)

Drop:  49.0m (LIDAR)

Dominance:  9.88% (LIDAR)

 

 

For details on the bwlch survey of Bryn Trillyn

For further details please consult the Trimble survey spreadsheet click {here}