Mapping Mountains – Trimble Surveys – Arenig Fach

01.03.14  Carnedd Iago (SH 782 406) and Llechwedd Deiliog (SH 785 398)

Carnedd Iago (SH 782 406)

After visiting the two hills of Y Garn and Pt. 477m (SH 758 375 and SH 758 378) Aled and I drove to the junction of the B4391 and proceeded toward Ffestiniog, where we parked next to the forest boundary at SH 788 395.  Parking can be found either on the northern side of this road where a forest track enters the conifer plantation or on the southern side where there is a relatively large graveled area.

We wanted to visit Carnedd Iago (SH 783 406) which has a 538m spot height at the summit on the Ordnance Survey 1:50,000 map, and the 502m summit of Llechwedd Deiliog (SH 785 398) which looked as if it may require a little tree bashing to get to its highest point.

It was spotting with rain when we set off and the sky didn’t look very promising for the remainder of the walk.  At least by keeping to the forest track we were a little sheltered.

Carnedd Iago is situated in the expanse of Y Migneint between Arenig Fach (SH 820 415) to its east and Cerrig y Ieirch (SH 758 425) to its north-west.  It really is a lonely and forgotten spot; if not for the nearness of the B road it would also be relatively remote for a hill in Wales.

We soon came to the small clearing in the trees where access to the open hill side can be found.  From here it’s a few minutes uphill to the highest point of Carnedd Iago.  As we approached the top the views opened up, we could see that the greyness that was playing with the coastal hills to the west had escaped and was now rapidly taking over the inland hills to our east.  However, the threatened rain was miraculously being kept at bay. 

Approaching the summit of Carnedd Iago

As we picked what we thought to be the highest point for the Trimble to gather 12 minutes of data, the hill ridges to the west were trying to emerge from their dark grey enshroudment.  Sometimes when the weather is turning inclement the cloud conditions can give sudden glimpses of accentuated ridges that otherwise may be taken for granted.

The Trimble GeoXH 6000 gathering data at the summit of Carnedd Iago

Looking toward the Moelwynion

Away to the north-east one building stood out amongst the loneliness of desolate moor – Cefngarw.  We’d visited this old farm house toward the end of December 2013 on our way to the summit of Bryn Mawr (SH 801 442).

Lonely Cefngarw

Toward the west the Rhinogydd looked at their impressive best, tinged in a primeval dullness with dark cloud empathising their roughness.  All highlighted with the smallest flash of light on cloud.  The mountains are quite magical whatever the time or weather, they never seem to disappoint.

The Rhinogydd looking grey and inviting

Rhinog Fach (L) and Rhinog Fawr (R)

Once the Trimble was packed away we headed down beside the forest edge to the bwlch that connects with Llechwedd Deiliog.  Our plan was to survey the bwlch and if the forestry permitted; also its summit.  As Aled stood beside the fence I ventured in to the land of the bwlch, which not surprisingly consisted of a bog.  The more I squashed my way around its domain the more methane gas was released, this was foul spelling.

A foul spelling bog is not the best to crawl around on your hands and knees trying to estimated where the hill to hill traverse meets the valley to valley traverse.  After a particularly unpleasant few minutes I picked a spot for Trimble placement with Aled verifying that this looked the best point, and set the Trimble on the ground to gather its customary data.

The Trimble GeoXH 6000 gathering data at the bwlch of Llechwedd Deiliog

The only place left to survey was the summit of Llechwedd Deiliog.  This is immersed in a conifer plantation which I had previously visited in May 2004 when conducting a basic leveling survey.  We pottered around in the forestry and having no clear sight from one possible high point to another, we eventually had to opt for a point to survey and found one that at least in its immediate vicinity looked to be the highest.  However, it was anyone's guess whether higher ground existed to our south.

Having set the Trimble up connected to its 2m pole we waited for nine minutes of data to be collected, then switched it off, packed the equipment away and headed back through to the trees to the forest track and the awaiting car below.  It proved an excellent couple of hours on the hill.

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 these results appear below. 

Survey Result

Carnedd Iago

Summit Height:  538.0m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 78271 40653 (Trimble GeoXH 6000)

Bwlch Height:  463.85m (LIDAR)

Bwlch Grid Reference:  SH 76016 43204 (LIDAR)

Drop:  74.15m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  13.78% (Trimble GeoXH 6000 summit and LIDAR bwlch)

Llechwedd Deiliog

Summit Height:  501.7m (LIDAR)

Summit Grid Reference:  SH 78522 39815 (LIDAR)

Bwlch Height:  481.2m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SH 78298 40196 (Trimble GeoXH 6000)

Drop:  20.6m (LIDAR summit and Trimble GeoXH 6000 bwlch)

Dominance:  4.10% (LIDAR summit and Trimble GeoXH 6000 bwlch)

For details on the bwlch survey of this hill

For further details please consult the Trimble Survey Spreadsheet