Mapping Mountains – Trimble Surveys – Aran and Bryniau Dyfi

08.03.14  Pen y Brynfforchog  (SH 817 179), Pt. 564.3m (SH 809 172) and Mynydd yr Hewyrch (SH 816 150), only bwlch surveyed

Pt. 564.3m (SH 809 172)

Spring is here!  The winter storms seem to be over and the sun is finally making an appearance as a predicted high pressure system is stabilising over the country.  However, high pressure systems can also bring murk and gloom, and so it was this morning, with the forecast of sunshine by midday.  Therefore I pottered about doing a variety of things before waiting for the first glimpse of the bright stuff before heading west to park at Bwlch Oerddrws (SH 802 170).

Two hills were on today’s agenda; Pen y Brynfforchog which is the most southerly of the Aran 2,000ft’s and Pt. 564.3m which is listed in Michael Dewey’s 500m list by a part invented name of Pen Ochr y Bwlch.

Bwlch Oerddrws is situated at the top of the A470 as it heads west from Dinas Mawddwy to Dolgellau and has a fairly large car park at its highest point.  To the north of this road rises a steep grassed slope with a helpful fence indicating the way up.  As progress is made up this slope the upper section of wire in the fence has been used as an aid in uphill momentum!

I was surprised to find a brisk breeze at the bwlch and as height was gained this turned into a buffeting wind.  Thankfully the strength of the wind was being funnelled up the hillsides and across the bylchau, so at least it wasn’t constant.

After the initial steep section is overcome a path contours around the bulk of Pt. 564m and heads towards its connecting bwlch with Pen y Brynfforchog.  This gave easy access to the latter hill and 90 minutes after leaving the car I was placing the Trimble close to the small summit cairn to gather data.

Pen y Brynfforchog (SH 817 179)

The Trimble GeoXH 6000 gathering data at the summit of Pen y Brynfforchog

Between this summit and the higher Aran is a conifer plantation that can be circumvented when heading toward Aran Fawddwy, but for those wishing to connect this hill up with the 600.5m summit of Y Gribin (SH 843 177) and the 541.9m summit of Foel Benddin (SH 853 165) (both heights are from surveys conducted by Alan Dawson with the blog author in attendance) a forest path is the most convenient way between the respective summits.  The conifer plantation has now largely been felled, with only haphazard pockets of trees remaining.  So the onward route to Y Gribin and Foel Benddin will now have views and hopefully the path hasn’t been destroyed by the tree felling.

Pen y Brynfforchog has an interesting listing history as its lower 656m summit at SH 818 185 had been designated the top in a number of published hill lists.  This was only rectified in 1974 when Phil Cooper listed the higher 685m summit at SH 817 179 in his single ring contour unpublished list.  The first published list to assign the higher 685m summit being in 1984 by Terry Marsh.

Once the Trimble had been packed away I headed back down beside the fence to the bwlch that connects Pen y Brynfforchog with Pt. 564m, I took data sets at two points.  The lower of the two and the one at the critical bwlch is nearer to the latter hill.

Gathering data at the first option for the bwlch of Pt. 564.3m

Gathering data at the second option for the bwlch of Pt. 564.3m

I then visited the summit of Pt. 564.3m which consists of an almost flat narrow ridge of grass which is rather unusual; I viewed this from opposing angles and chose my spot for the Trimble to be placed.  This hill was not included in Michael’s original 500-Metre Tops of England and Wales list and only entered the listing after a 115ft (35.1m) basic levelling survey I conducted for drop on the 28^th April 2000.  If memory serves me right I proposed the name of Ochr y Bwlch to Michael as this name appears on the OS map (although the hill is not known locally as this) and it was Rob Woodall who suggested adding the ‘Pen’ part to designate that the name applied to the ‘top’ of the hill, apologies to Mr Woodall if my memory is not wholly factual. 

  

The summit of Pt. 564.3m (SH 809 172)

As the Trimble gathered its data I looked out toward Cadair Idris to the west and down the A470 as it follows the course of the Afon Cerist toward Dinas Mawddwy.  Above this rose Mynydd yr Hewyrch, grand in its bulk and profile.

Cadair Idris from the southern Aran

Mynydd yr Hewyrch (SH 816 150) from the southern Aran

The downward route on the steep slope back to the car proved a little quicker than the upward slog.  Adjacent to the car park is the critical bwlch for Mynydd yr Hewyrch, the Ordnance Survey map has a 363m spot height on the road, but the bwlch is lower than the road and if not for a slightly raised section of land next to a fence that heads toward the next hill of Cribin Fawr (SH 794 153) the whole area would be a wet bog.  This raised section has the beginnings of a water course on its immediate west and another one a few metres away on its east; I placed the Trimble on the eastern edge of the raised section of land trying not to submerge it in the bog in the process.  Once ten minutes of data were collected I packed it away and headed up to Nantlle for the weekend.

Survey Result:

Pen y Brynfforchog

Summit Height:  685.0m (converted to OSGM15)

Summit Grid Reference:  SH  81776 17959

Bwlch Height:  614m (spot height)

Bwlch Grid Reference:  SH 82207 18618 (spot height)

Drop:  71m (Trimble GeoXH 6000 summit and spot height bwlch)

Dominance:  10.36% (Trimble GeoXH 6000 summit and spot height bwlch)

 

Pt. 564.3m

Summit Height:  564.3m (converted to OSGM15)

Summit Grid Reference:  SH 80957 17269

Bwlch Height:  530.5m (converted to OSGM15)

Bwlch Grid Reference:  SH 81133 17386

Drop:  33.8m (Dodd, Dewey and 500m Twmpau status confirmed)

Dominance:  5.99%

Mynydd yr Hewyrch

Summit Height:  678.3m (converted to OSGM15, from subsequent Trimble GeoXH 6000 survey) 678.5m (from subsequent Leica RX1250 survey) (significant height revision)

Summit Grid Reference:  SH 81697 15003

Bwlch Height:  360.5m (converted to OSGM15)

Bwlch Grid Reference:  SH  80208 17001

Drop:  318.0m (based on Trimble GeoXH 6000 bwlch and Leica RX1250 summit)

Dominance:  46.87% (based on Trimble GeoXH 6000 bwlch and Leica RX1250 summit) (Lesser Dominant status confirmed) 

The basic levelling survey conducted on the hill known as Pt. 564.3m in April 2000 gives good accordance with the data produced by the Trimble as Pt. 564.3m has 33.8m of drop (35.1m from the basic levelling survey), whilst current Ordnance Survey data has a bwlch spot height of 533m (enlarged Geograph map) and a summit spot height of 564m, giving a drop of 31m.

For details on the summit survey of Mynydd yr Hewyrch

For further details please consult the Trimble Survey Spreadsheet