Mapping Mountains – Trimble Surveys – Moel Siabod

25.02.23  Moel Siabod (SH 705 546, only bwlch surveyed) and Cefn y Cerrig (SH 674 545) 

Having scrutinised several OS maps a circular walk was devised from the viewing-point car park (SH 658 541) between Llyn Gwynant and Pen y Gwryd.  I had never started a hill walk from this point and found the idea rather novel.  I arrived just after 8am and soon set off along the road to Pen y Gwryd, flanked by a stunning view of Yr Wyddfa.  Remnants of recent snowfall speckled the upper slopes and the buffeting of a cold north-easterly reminded me that winter was not yet over. 

Yr Wyddfa looking resplendent as ever (Photo: Aled Williams)

As I approached Pen y Gwryd, the masses bound for Yr Wyddfa were already filling up the available roadside car parking spaces.  I slipped by unnoticed as I headed to the first of my surveying objectives; the critical bwlch of Moel Siabod.  I had assisted Myrddyn Phillips with the survey of this pass back in 2017 and was eager to collect a couple of extra data sets given that the drop result was so close to the 600m prominence threshold for Major status (hills that appear in Mark Trengove’s list The Major Mountains of Britain and Ireland).  Two data sets were taken at the bwlch, each involving a lonely five-minute vigil in the numbing chill of the north wind. 

Gathering data at the bwlch of Moel Siabod (Photo: Aled Williams)

The view toward Cefn y Cerrig (Photo: Aled Williams)

Having packed away the Trimble, I headed towards the high point of the day; the potential new Welsh Highlands Sub of Cefn y Cerrig.  It felt good to be out on the open mountain, although the underfoot conditions made the traverse of the moor a squelchy affair.  Drier conditions prevailed once on the arm of Cefn y Cerrig was reached and a leisurely walk soon brought me to the base of the summit tor. 

The view of Dyffryn Mymbyr (Photo: Aled Williams) 

Gathering data at the summit of Cefn y Cerrig (Photo: Aled Williams)

I had visited the summit of Cefn y Cerrig once before in December 2005 and my memory of it as a fine rocky top was affirmed by the stunning view of Dyffryn Mymbyr.  This time, there was work to do.  The high point was duly located and the Trimble was placed into position for measurement.  During data collection I sheltered in comfort on the south-western side of the summit rocks and spied my descent route. 

Gathering data at the bwlch of Cefn y Cerrig with Yr Wyddfa as backdrop (Photo: Aled Williams)

Cefn y Cerrig (Photo: Aled Williams)

Once the Trimble had completed its task, I scrambled down the rocky facade of Cefn y Cerrig to the bwlch connecting it to its parent peak; Clogwyn Bwlch y Maen.  The critical position was located beside a partially frozen pool and the final data set of the day was gathered shortly afterwards.  The ground between Cefn y Cerrig and the car was pathless and wet, but quick progress was made regardless.  The sudden appearance of Llyn Gwynant signalled my imminent arrival back at the car and the end of an enjoyable morning on the hill.

Heading down from the hill (Photo: Aled Williams)

 

Survey Result: 

 

Moel Siabod

Summit Height:  872.2m (converted to OSGM15, from previous Trimble GeoXH 6000 survey)

Summit Grid Reference:  SH 70524 54631 (from previous Trimble GeoXH 6000 survey)

Bwlch Height:  272.3m (converted to OSGM15)

Bwlch Grid Reference:  SH 66044 55603 (from previous Trimble GeoXH 6000 survey)

Drop:  599.9m (P600 Major deletion)

Dominance:  68.78%  

Cefn y Cerrig

Summit Height:  502.0m (converted to OSGM15)

Summit Grid Reference:  SH 67480 54509

Bwlch Height:  491.2m (converted to OSGM15)

Bwlch Grid Reference:  SH 67511 54413

Drop:  10.8m (Welsh Highland Sub addition)

Dominance:  2.14%

For details on the 1st bwlch survey of Moel Siabod

For details on the summit survey of Moel Siabod

For further details please consult the Trimble Survey Spreadsheet

 

 

 

  

Mapping Mountains – Hill Reclassifications – Major Mountains of Britain and Ireland

Moel Siabod (SH 705 546) – Major deletion

There has been a deletion to the list of the Major Mountains of Britain and Ireland, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and Aled Williams, with the bwlch position based on LIDAR analysis conducted by Aled Williams.

Moel Siabod (SH 705 546)

The criteria for the list that this deletion applies to are:

The Major Mountains of Britain and Ireland - British and Irish hills that have 600m or more of drop.  This list was first published in a downloadable leaflet format by Europeaklist in February 2010.  Its author; Mark Trengove originally listed 119 qualifying hills, with these comprising 82 hills in Scotland, 25 hills in Ireland, 7 hills in Wales, 4 hills in England and 1 hill in the Isle of Man, with a further five Scottish hills listed that fail to qualify by 10m or less of drop.

The Major Mountains of Britain and Ireland by Mark Trengove

The name the hill is listed by is Moel Siabod, and it is positioned with the A5 road to its north-east, the A4086 road to its north-west and the A498 road to its west, and has the small community of Capel Curig towards its north north-east.

When this list was originally published this hill was not included as it was documented with 595m of drop, based on the 872m summit spot height that is adjoined to a triangulation pillar and the 277m spot height that appears on the area of the bwlch on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.  However, the 277m spot height appears on a road which is above the position of the critical bwlch.

Extract from the Ordnance Survey 1:25,000 Explorer map

Since the original publication of this list there have been a number of Ordnance Survey maps made available online, some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website, whilst others are current and digitally updated such as the old Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map.

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available maps and for this hill it had a 272m bwlch spot height positioned at SH 66071 55625, and when coupled with the 872m summit spot height gave this hill 600m of drop.

Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website

However, it was not until the survey with the Trimble GeoXH 6000 that the details for this hill could be accurately re-assessed.  This resulted in a 872.2m summit height, with the author of the list present during this survey, and a 272.3m bwlch height, with the latter position based on LIDAR analysis.  With these vales giving this hill 599.9m of drop.  

Gathering data at the critical bwlch of Moel Siabod

Gathering data at the summit of Moel Siabod

Therefore, the deletion of this hill from Major status was accepted by Mark Trengove and announced in his photo blog on the Relative Hills of Britain Facebook page on the 14.03.18, with this deletion augmented in to the listing of the Major Mountains of Britain and Ireland resulting in the total reverting to 119 qualifying hills.

The full details for the hill are:

Name:  Moel Siabod

OS 1:50,000 map:  115

OS 1:25,000 map:  18

Summit Height:  872.2m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 70524 54631

Bwlch Height:  272.3m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SH 66044 55603

Drop:  599.9m

Myrddyn Phillips (April 2018)

Mapping Mountains – Trimble Surveys – Moel Siabod

11.03.18  Garreg Amlwg (SH 717 549), Moel Siabod (SH 705 546), Pt. 815.9m (SH 708 550), Pt. 811.2m (SH 709 551) and Pt. 800.8m (SH 711 552)

Garreg Amlwg (SH 717 549)

For many years it seemed as if I was walking with blinkers on, being preoccupied with the 2,000ft mountains of Wales with little regard for visiting lower heighted hills.  Nowadays I get pleasure enough on the lower P30s, but when opportunity arises to visit the higher hills their dramatic architecture is savoured, and today was such an occasion as along with Mark and Aled we planned on visiting Moel Siabod and a number of lower satellite peaks whose existing and potential P15 status needed clarifying.

Moel Siabod is a wonderful hill set apart from its higher neighbours, its 872m map heighted summit commands extensive views and is a relative recent addition to Mark’s P600 Majors list, only entering this list as the 272m bwlch spot height that appears on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website gives the hill 600m of map spot heighted drop.

Having left three cars at different points for optional descent routes we ascended via Pont Cyfyng, walking up the narrow lane to the footpath gaining the track leading to the north-eastern ridge of Moel Siabod, across the valley spring sunshine picked out the rugged profile of Creigiau Gleision and the pyramidal shape of Pen Llithrig y Wrach.  However, the sunshine was not to last as high greying cloud would slowly ebb in from the south adding wisps to the higher tops with the prospect of incoming rain.

Creigiau Gleision

Pen Llithrig y Wrach

The first hill we wanted to investigate is listed as an Uchaf, these are the Welsh P15 hills at and over 500m in height, and the hill only entered this list through a basic levelling survey conducted in July 2004.  Following a path toward a quarry lake the hill rose above slightly rounded and elongated in profile it sits away from its much higher neighbour and is probably seldom visited and yet it is situated in a marvellously wild landscape of heather moor, bog and rock.

Moel Siabod looked dramatically appetising as we descended to the hill’s connecting bwlch which has a number of small attractive pools situated on it, we judged where the critical bwlch lay and as I set the Trimble up and floundered in the overly wet bog adjacent to the larger of these pools, Mark and Aled headed off to investigate if there was an outflow from the opposing side of the pool.

Descending to the connecting bwlch of Garreg Amlwg

Mark with Moel Siabod as backdrop

Gathering data at the area of the bwlch of Garreg Amlwg

This hill has two tops and both were Trimbled, with each summit consisting of a large rock.  As the more north-westerly top was Trimbled Mark and Aled visited the south-easterly one, I looked out as they waited on this summit with the cliff face of Moel Siabod as backdrop rising skyward dwarfing our position.

Gathering data from what proved to be the lower of the two tops

Aled and Mark on the south-westerly top of Garreg Amlwg

Gathering data from the summit of Garreg Amlwg

Leaving the hill we followed a narrow path across the outflow from Llyn y Foel and joined the lower part of Daear Ddu, which if wanting a scramble is the way to approach Moel Siabod.  Daear Ddu is the eastern ridge of Moel Siabod and I’ve enjoyed its rock on many occasions, the first being with a horrendous hangover when I was sick on the hill, not a pretty sight!

Beside Llyn y Foel

As height was gained the view opened, down upon Llyn y Foel and across the Eryri peaks to the far off Berwyn and Bryniau Clwyd.  The ridge was fun, as it ever is, with just enough hand on rock to bring a sustainable amount of enjoyment.

Llyn y Foel

The north-eastern ridge of Moel Siabod with the three tops which were later surveyed

By the time we crested the summit ridge cloud had built and as the Trimble clung aligned to the highest rock gathering its all-important data, mist quickly rolled in and would remain with us until we descended.

The north-eastern ridge from close to the summit of Moel Siabod

The view south-west just before the mist rolled in

Gathering data at the summit of Moel Siabod

If time permitted we hoped to survey at least two of the three tops on the upper part of the north-easterly ridge of Moel Siabod, each is a jumble of rock with two of the three bylchau being tight with plunging drops nearby down horrendously steep gulleys.

After the Trimble had gathered its allotted data from the summit of Moel Siabod I joined Mark and Aled in the large wind shelter just below the high point for a bite to eat before continuing to the three rocky tops. 

As we walked through the mist toward the first connecting bwlch we discussed the merits of what ones to survey as dusk would be approaching on our descent and as the weather had closed in it looked as if the forecast rain would overtake us, these weren’t ideal conditions to survey castellated summits above mighty drops.  The impending problem was solved when Aled suggested a two minute data set at each bwlch and summit, this is the minimum suggested for data collection by Trimble.  This would enable the three tops to be surveyed in turn and would complete all tops adjoined to Moel Siabod then having been Trimbled.

The ridge proved fun as the rock was damp with rock step after rock step negotiated from one summit to bwlch and onward to the next summit.  These surveys came thick and fast with barely a moment to contemplate some of the Trimble bwlch positions with two being on the edge of mountainous drops down steep gulleys.

A precarious position for a Trimble

As the last summit was Trimbled Mark headed down to a fence which gave access to the path leading to where one of our cars was parked beside Plas y Brenin and Llynnau Mymbyr, Aled and I soon followed.

Gathering data  from the summit of Pt. 800.8m

It had been a good day on the hill with ten surveys completed, with an enjoyable time picking out an occasional scramble whilst visiting the summit of one of Eryri’s special mountains.  We ended the day in the Bryn Tyrch at Capel Curig with good conversation and a welcome meal.

Postscript:  Since the survey of these hills, the LIDAR (Light Detection & Ranging) technique is now being used to produce accurate height and position for hills.  Therefore, numerical data produced by surveying with the Trimble GeoXH 6000 is being updated.  However, each individual data set is analysed and as data produced by the Trimble GeoXH 6000 is considered more accurate it is this relative to the position produced by LIDAR that is prioritised.

   

Survey Result:

Garreg Amlwg

Summit Height:  561.6m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 71781 54962 (Trimble GeoXH 6000)

Bwlch Height:  546.5m (converted to OSGM15, Trimble GeoXH 6000 adjusted height relative to LIDAR position)

Bwlch Grid Reference:  SH 71738 55023 (LIDAR)

Drop:  15.1m (Trimble GeoXH 6000 summit and Trimble GeoXH 6000 adjusted bwlch height relative to LIDAR position)

Dominance:  2.69% (Trimble GeoXH 6000 summit and Trimble GeoXH 6000 adjusted bwlch height relative to LIDAR position)

Moel Siabod

Summit Height:  872.2m (converted to OSGM15)

Summit Grid Reference:  SH 70524 54631

Bwlch Height:  272.3m (converted to OSGM15) (from previous Trimble GeoXH 6000 survey)

Bwlch Grid Reference:  SH 66044 55603 (from previous Trimble GeoXH 6000 survey)

Drop:  599.9m (P600 Major deletion)

Dominance:  68.78%

Pt. 815.9m

Summit Height:  815.9m (converted to OSGM15)

Summit Grid Reference:  SH 70859 55036

Bwlch Height:  808.9m (converted to OSGM15)

Bwlch Grid Reference:  SH 70797 54991

Drop:  7.0m

Dominance:  0.86%

Pt. 811.2m

Summit Height:  811.2m (converted to OSGM15)

Summit Grid Reference:  SH 70955 55120

Bwlch Height:  803.9m (converted to OSGM15)

Bwlch Grid Reference:  SH 70898 55084

Drop:  7.3m

Dominance:  0.90%

Pt. 800.8m

Summit Height:  800.8m (converted to OSGM15)

Summit Grid Reference:  SH 71115 55231

Bwlch Height:  787.5m (converted to OSGM15)

Bwlch Grid Reference:  SH 71076 55224

Drop:  13.3m

Dominance:  1.66%

For details on the 1st bwlch survey of Moel Siabod

For details on the 2nd bwlch survey of Moel Siabod

For further details please consult the Trimble Survey Spreadsheet

Mapping Mountains – Hill Reclassifications – Major Mountains of Britain and Ireland

Moel Siabod (SH 705 546) – Major addition

There has been an addition to the list of the Major Mountains of Britain and Ireland, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary Ordnance Survey maps.

Moel Siabod (SH 705 546)

The criteria for the list that this addition applies to are:

The Major Mountains of Britain and Ireland - British and Irish hills that have 600m or more of drop.  This list was first published in a downloadable leaflet format by Europeaklist in February 2010.  Its author; Mark Trengove originally listed 119 qualifying hills, with these comprising 82 hills in Scotland, 25 hills in Ireland, 7 hills in Wales, 4 hills in England and 1 hill in the Isle of Man, with a further five Scottish hills listed that fail to qualify by 10m or less of drop.

The Major Mountains of Britain and Ireland by Mark Trengove

The name the hill is listed by is Moel Siabod, and it is positioned with the A5 road to its north-east, the A4086 road to its north-west and the A498 road to its west, and has the small community of Capel Curig towards its north north-east.

When this list was originally published this hill was not included as it was documented with 595m of drop, based on the 872m summit spot height that is adjoined to a triangulation pillar and the 277m spot height that appears on the area of the bwlch on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.  However, the 277m spot height appears on a road which is above the position of the critical bwlch.

Extract from the Ordnance Survey 1:25,000 Explorer map

Since the original publication of this list there have been a number of Ordnance Survey maps made available online, some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website, whilst others are current and digitally updated such as the old Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map.

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available maps and for this hill it had a 272m bwlch spot height positioned at SH 66071 55625, and when coupled with the 872m summit spot height gave this hill 600m of drop.

Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website

These details and the prospective addition of this hill to the Majors were conveyed to Mark Trengove; the author of the list in January 2016.  And the addition of this hill to Major status was accepted by the list author and its new classification augmented in to the listing of the Major Mountains of Britain and Ireland in January 2016 increasing the total of qualifying hills to 120. 

The full details for the hill are:

Name:  Moel Siabod

OS 1:50,000 map:  115

OS 1:25,000 map:  18

Summit Height:  872m (trig pillar)

Summit Grid Reference:  SH 70528 54633 (trig pillar)

Bwlch Height:  272m (spot height)

Bwlch Grid Reference:  SH 66071 55625 (spot height)

Drop:  600m (trig pillar summit and spot height bwlch)

Myrddyn Phillips (April 2018)