Showing posts with label Foel y Geifr. Show all posts
Showing posts with label Foel y Geifr. Show all posts

Tuesday, 11 July 2023

Mapping Mountains – Hill Reclassifications – 500m Twmpau


Foel y Geifr (SH 716 050) – 500m Twmpau reclassified to 500m Sub-Twmpau

There has been a reclassification to the listing of the 500m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail produced by Joe Nuttall in his surface analysis progamme, with subsequent LIDAR analysis conducted by the DoBIH team and independently by Aled Williams and Myrddyn Phillips. 

Foel y Geifr (SH 716 050)

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

500m Twmpau - Welsh hills at or above 500m and below 600m in height with 30m minimum drop, with an accompanying sub list entitled the 500m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 500m and below 600m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.  The list is authored by Myrddyn Phillips and is available to download in Google Doc format from Mapping Mountains. 

The 500m Twmpau by Myrddyn Phillips

The name the hill is listed by is Foel y Geifr and it is adjoined to the Tarren y Gesail group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and it is positioned with the B4405 road to its north-west, the A493 road to its south and the A487 road to its east, and has the town of Machynlleth towards the south-east.

When the list that later became known as the 500m Twmpau was first compiled, this hill was included in the main P30 list due to a basic levelling survey conducted by Myrddyn Phillips on the 26th June 2000 that resulted in over 30m of drop, and listed with a 515m summit height, based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map and a 483m bwlch height; relative to the drop value ascertained from the basic levelling survey and the summit spot height. 

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

Since the original compilation of this list there have been a number of 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 were digitally updated such as the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map, whilst others are current and digitally updated such as the interactive mapping on the Magic Maps and WalkLakes websites.

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 Ordnance Survey maps and for this hill it had a 486m bwlch spot height and when coupled with its 515m summit spot height, these values gave this hill 29m of drop.  This emphasised the uncertainty applicable to the result produced by the basic levelling survey. 

LIDAR image of Foel y Geifr (SH 716 050)

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the reclassification of this hill to 500m Sub-Twmpau status is due to LIDAR analysis, resulting in a 515.6m summit height and a 486.8m bwlch height, with these values giving this hill 28.8m of drop, which is insufficient for it to be classified as a 500m Twmpau. 

 

The full details for the hill are:

Group:  Tarren y Gesail

Name:  Foel y Geifr

OS 1:50,000 map:  124

Summit Height:  515.6m (LIDAR) 

Summit Grid Reference:  SH 71634 05092 (LIDAR) 

Bwlch Height:  486.8m (LIDAR) 

Bwlch Grid Reference:  SH 71726 05403 (LIDAR) 

Drop:  28.8m (LIDAR)

 

Myrddyn Phillips (July 2023)

 

  

Tuesday, 4 July 2023

Mapping Mountains – Hill Reclassifications – The 500-Metre Tops of England and Wales – Deweys


Foel y Geifr (SH 716 050) – Dewey deletion

This is one in a series of Hill Reclassification posts that detail hills whose status has altered in the listing of the Deweys.  These posts tie in with a ChangeRegister giving detail to this list and its alterations since publication in the Mountain tables book. 

Foel y Geifr (SH 716 050)

The 500-Metre Tops of England and Wales are affectionately known after their hill list compiler; Michael Dewey.  This list mixes metric and imperial height in its criteria to bookend up to the 2000ft height band and takes in all hills in England, Isle of Man and Wales that are 500m and above and below 2000ft (609.6m) in height that have 30m minimum drop.

This list formed one of a number of lists that appeared in the Mountain tables book published by Constable in 1995 and at the time of publication comprised 373 hills with 164 in England, 5 in the Isle of Man and 204 in Wales.  The Deweys have undergone extensive revision since first publication with the initial stages forming the basis of this revision given below: 

 

1995    Mountain tables published by Constable with 373 hills listed as Deweys.

 

April 2000    Strider (LDWA quarterly booklet) publishes contact details for David Purchase and Myrddyn Phillips who have found and list 24 and 14 possible new 500m tops respectively.

 

It was expanded versions of the above two lists that formed the basis of the next publication:

 

25th May 2000    List of Possible 500 Metre Tops by Michael Dewey listing 44 hills.

 

David Purchase expands his Additional Dewey 500m Hills and Myrddyn Phillips produces lists of English 500m hills to measure and Welsh 500m hills to measure.

 

These lists formed the basis of the next publication:

 

29th June 2000    Possible/Probable 500’s by Michael Dewey listing 77 hills.  Michael adopts following protocol; if one person proposes that a top should qualify as a 500 by personal survey, and is then confirmed by a second person, it should then be promoted to the main list.

 

April 2002    The 500+ Tops of England and Wales – The ‘New Deweys’ published in the Strider booklet and listing 66 new qualifying hills.

 

25th May 2006    Rob Woodall republishes Michael’s main and possible/probable lists on the RHB Yahoo group file database.

 

Postscript:  Michael Dewey died on the 5th November 2022.  His wife; Gillian wished for this list to be carried on and made provision for it to be co-authored by Myrddyn Phillips.  Michael will always be the compiler and originator, it’s just that he’s now got a co-author to safeguard and carry this list on.

Mountain tables by Michael Dewey

The details for this deletion appear below:

The name the hill is listed by in the Deweys is Foel y Geifr, and it is adjoined to the Cadair Idris group of hills which are situated in the south-western part of North Wales, and it is positioned with the B4405 road to its north-west, the A493 road to its south and the A487 road to its east, and has the town of Machynlleth towards the south-east.

This hill was not included in the original 1995 Constable publication, but with a 515m summit spot height and bwlch contouring between 480m – 490m that appear on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, the interpolated drop value was estimated sufficient for this hill to be a potential new Dewey. 

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

The above detail was noted by Myrddyn Phillips who then conducted a basic levelling survey of this hill on the 26th June 2000, resulting in over 30m of drop.  These details were forwarded to the list author; Michael Dewey and the hill was added to the list with the date of survey given in the Remarks column accompanying the list.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR image of Foel y Geifr (SH 716 050)

Therefore, the deletion of this hill from the The 500-Metre Tops of England and Wales list was instigated on the 26th May 2023 and is due to LIDAR analysis first reported by the DoBIH team based on detail produced by Joe Nuttall in his surface analysis programme, resulting in a 515.6m summit height and a 486.8m bwlch height, with these values giving this hill 28.8m of drop, which is insufficient for it to be classified as a Dewey. 

 

The full details for the hill are: 

Name:  Foel y Geifr 

OS 1:50,000 map:  124

OS 1:25,000 map:  23

Summit Height:  515.6m (LIDAR) 

Summit Grid Reference:  SH 71634 05092 (LIDAR) 

Bwlch Height:  486.8m (LIDAR) 

Bwlch Grid Reference:  SH 71726 05403 (LIDAR) 

Drop:  28.8m (LIDAR) 

 

Myrddyn Phillips (July 2023)

  

Thursday, 11 June 2020

Mapping Mountains – Hill Reclassifications – The 500-Metre Tops of England and Wales – Deweys



THIS HILL HAS SUBSEQUENTLY BEEN DELETED FROM THE DEWEY LIST


Foel y Geifr (SH 716 050) – Dewey addition

This is one in a series of retrospective Hill Reclassification posts that detail hills whose status has altered in the listing of the Deweys and where I have had direct association with the status change.  These posts will tie in with a forthcoming Change Register giving detail to this list and its alterations since publication in the Mountain tables book.

Foel y Geifr (SH 716 050) on left with Tarren y Gesail on the right

The 500-Metre Tops of England and Wales are affectionately known after their hill list compiler; Michael Dewey.  This list mixes metric and imperial height in its criteria to bookend up to the 2000ft height band and takes in all hills in England, Isle of Man and Wales that are 500m and above and below 2000ft (609.6m) in height that have 30m minimum drop.

This list formed one of a number of lists that appeared in the Mountain tables book published by Constable in 1995 and at the time of publication comprised 373 hills with 164 in England, 5 in the Isle of Man and 204 in Wales.  The Deweys have undergone extensive revision since first publication with the initial stages forming the basis of this revision given below:


1995    Mountain tables published by Constable with 373 hills listed as Deweys.

April 2000    Strider (LDWA quarterly booklet) publishes contact details for David Purchase and Myrddyn Phillips who have found and list 24 and 14 possible new 500m tops respectively.

It was expanded versions of the above two lists that formed the basis of the next publication:

25th May 2000    List of Possible 500 Metre Tops by Michael Dewey listing 44 hills.

David Purchase expands his Additional Dewey 500m Hills and Myrddyn Phillips produces lists of English 500m hills to measure and Welsh 500m hills to measure.

These lists formed the basis of the next publication:

29th June 2000    Possible/Probable 500’s by Michael Dewey listing 77 hills.  Michael adopts following protocol; if one person proposes that a top should qualify as a 500 by personal survey, and is then confirmed by a second person, it should then be promoted to the main list.

April 2002    The 500+ Tops of England and Wales – The ‘New Deweys’ published in the Strider booklet and listing 66 new qualifying hills.

25th May 2006    Rob Woodall republishes Michael’s main and possible/probable lists on the RHB Yahoo group file database. 

 
Mountain tables by Michael Dewey

The details for this addition appear below:

The name the hill is listed by in the Deweys is Foel y Geifr, and it is adjoined to the Cadair Idris group of hills which are situated in the south-western part of North Wales, and it is positioned with the B4405 road to its north-west, the A493 road to its south and the A487 road to its east, and has the town of Machynlleth towards the south-east.

This hill was not included in the original 1995 Constable publication, but with a 515m summit spot height and bwlch contouring between 480m – 490m that appear on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, the interpolated drop value was estimated sufficient for this hill to be a potential new Dewey.

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

The above detail was noted by Myrddyn Phillips who then conducted a basic levelling survey of this hill on the 26th June 2000, resulting in 104½ft / 31.9m of drop.  These details were forwarded to the list author; Michael Dewey and the hill was added to the list with the date of survey given in the Remarks column accompanying the list.


The full details for the hill are:

Name:  Foel y Geifr

OS 1:50,000 map:  124

OS 1:25,000 map:  23

Summit Height:  515m (spot height)

Summit Grid Reference:  SH 71636 05099 (hand-held GPS via DoBIH)

Bwlch Height:  483m (relative to spot heighted summit and basic levelling survey drop)

Bwlch Grid Reference:  SH 71733 05408 (interpolation)

Drop:  32m (spot height summit and basic levelling survey drop)


Myrddyn Phillips (June 2020)


Tuesday, 25 October 2016

Mapping Mountains – Trimble Surveys – Y Berwyn


19.10.16  Foel y Groes (SH 918 235), Moel y Cerrig Duon (SH 923 241), Pt. 605.7m (SH 918 257), Cefn Coch (SH 923 266), Foel y Geifr (SH 937 275), Trum y Gwragedd (SH 941 284, bwlch only) and Foel Cedig (SH 981 283, bwlch only [SH 944 273])

Moel y Cerrig Duon (SH 923 241)

Parts of the Berwyn have a reputation as being pathless heather bound wonders of torture, whilst other parts are just heather bound.  Today we encountered the former as tussocks; moor grass and heather stretched away in a sea of wilderness which is probably seldom visited except for the occasional sheep gatherer and peak bagger.

The land we visited stretches between Bwlch y Groes and Cwm Hirnant and consists of a number of 500m and 600m hills, all are bulbous affairs of heather and moor where solitude and pathless wandering is the order of the day.

I was out with Alan and we planned to survey everything we could, I met him at the high point of the road that heads from the northern extremity of Llyn Efyrnwy (Lake Vyrnwy) to Y Bala, leaving one car here we continued to Bwlch y Groes, which was where my interest in mountain surveying first cast its hold over me many a year ago when I met Dewi Jones in the car park and he told me that the Nuttall’s had missed a hill from their listing of Welsh mountains, and that he’d surveyed it as having over 15m of drop.  This chance meeting was in the late 1990’s and it led me down a rather unusual but very fulfilling surveying route that was totally unexpected.

As Alan got his autumnal wellies on I positioned the Trimble on top of my rucksack on the edge of the road beside the entrance to the large gravelled and rocky parking area at the top of Bwlch y Groes for the first of what proved to be 14 surveys of the day, this was for the critical bwlch of Moel y Cerrig Duon.

Surveying the critical bwlch of Moel y Cerrig Duon on the edge of the road at Bwlch y Groes

Once data were collected I headed up beside a fence on a narrow path which led toward the summit of Moel y Cerrig Duon, on the way is an Uchaf; Foel Groes, which is also the watershed summit of Wales, as drainage to its south flows into the Afon Dyfi (River Dovey) and Cardigan Bay, whilst drainage to its east flows into the Afon Hafren (River Severn) and the Bristol Channel and drainage to its north flows into the Afon Dyfrdwy (River Dee) and Liverpool Bay.

By the time the Trimble was being set up on the first of two potential summit positions for Foel y Groes, Alan had caught up, and as the second summit position was surveyed he headed off toward the higher summit of Moel y Cerrig Duon leaving me to survey the bwlch between.  This was the start of a system that worked extremely well with Alan heading off to find the next position to survey, leaving me to gather data with the Trimble where he had just surveyed with his Leica; this system remained with us all day.

Gathering data at the summit of Foel y Groes with (L-R) Pt. 605.7m and Moel y Cerrig Duon in the background

To our north and west the sky massed an ominous grey as dark showers broke out on the higher hills, and although the morning’s rain has ceased the thread of showers remained with us for the remainder of the walk.  The overhead conditions gave us an occasional flash of autumnal colour as deep greys of sky were highlighted by flashes of sunlight brightening an otherwise featureless and monochrome scene of mountain and moor.

When I joined Alan on the summit of Moer y Cerrig Duon his Leica was already gathering data beside the summit cairn, and once 22 minutes of data were collected he set off north-west toward a wilderness of open land that is pathless.  After the Trimble had gathered its customary five minutes of data I followed.  The going was uneven and a little tough in places, but just being there was compensation enough as I’d only joined the hills of Moel y Cerrig Duon with Foel y Geifr once before; with my Mother and her second husband; Barry, many a year ago, my memories from that day was of a great swathe of featureless tough moorland heather bashing, and the course of time has not diminished the nature of this land.

Alan beside the Leica RX1250 at the summit of Moel y Cerrig Duon


Gathering data with the Trimble GeoXH 6000 at the summit of Moel y Cerrig Duon

As I slowly stumbled my way down toward Alan who was assessing the lay of land and choosing his spot for Leica placement at the critical bwlch of Foel y Geifr, I looked toward the west as a great mass of blackened cloud enveloped the Arennig, being high when showers are breaking out is somewhat fulfilling as one can watch their course, this can sometimes be disconcerting as showers are prone to head the same way that you are going, and the going can then get rather wet, but on occasion showers can follow the course of valleys and break out either side of the hill you are on, leaving a pleasing feeling of dryness.

Alan beside the Leica RX1250 at the critical bwlch of Foel y Geifr


Foel y Geifr from its critical bwlch


Gathering data with the Trimble GeoXH 6000 at the critical bwlch of Foel y Geifr

As I joined Alan we had a quick chat before his Leica was packed away and my Trimble assembled over the same spot, next stop was the summit of a 606m map heighted Simm and Dewey, I followed Alan up the hill on pathless moor that developed in to a bed of wet peat toward the summit.  Once Alan’s Leica had gathered the customary 20 minutes of data he headed down to the next bwlch and I positioned the Trimble over the same spot and gathered five minutes of data, and then proceeded down to the next bwlch where the Leica was already in position. 

Nearing the summit of Pt. 605.7m (SH 918 257)


Approaching the summit of Pt. 605.7m (SH 918 257)


The Leica RX1250 gathering data at the summit of Pt. 605.7m


Pt. 605.7m (SH 918 257)


The Trimble GeoXH 6000 gathering data at the summit of Pt. 605.7m

The bwlch of the 606m map heighted hill was soon surveyed before I joined Alan on the summit of Cefn Coch which is listed as a Dewey with 31m of drop, this drop value is based on a rudimentary survey I conducted with Rob Woodall on the 28th October 2001, the result was sent to Michael Dewey who then promoted Cefn Coch to his 500m list of English and Welsh hills.  Since then the Ordnance Survey enlarged mapping on the Geograoh website has become available and shows a 565m spot height at this hill’s bwlch and when coupled with its 594m summit spot height, only gives this hill 29m of map drop, which is insufficient for Dewey qualification, it will be good to finally confirm this hill’s drop value and status, as well as having another comparison of data between my old rudimentary staff and the Trimble.

Once on the summit area Alan set his Leica up on what looked like the high point and suggested that I could Trimble this point and another which looked close in height, each was separated by a small cleft of land, Alan used a Disto to sight from one to the other and confirmed that the further westerly point, where his Leica was now gathering data, was just higher.   The same procedure then took place with the Leica set up first and gathering around 20 minutes of data, and after the Trimble had gathered one set of data at the slightly lower point it was positioned at the same point as the Leica and gathered a further five minutes data set.

Alan's Leica gathering data at the summit of Cefn Coch whilst the Trimble gathers data at what proved to be a lower point


The Trimble GeoXH 6000 gathering data at the summit of Cefn Coch

The bwlch for Cefn Coch proved another wondrous affair of featureless and wild moor where few must wander.  However featureless it proved the critical point was relatively easy to pinpoint and as I joined Alan he had already assembled his Leica RX1250 and it was gathering another 20 minute data set.

Somewhere down there is Alan setting up the Leica RX1250


The Leica RX1250 gathering data at the critical bwlch of Cefn Coch

As the Trimble gathered data at the bwlch, Alan set off toward the summit of Foel y Geifr, the ground looked pathless and we hoped that a semblance of path may exist adjacent to a fence that was later joined and headed toward the last summit of the day.  It was unusual but also pleasing to be left on my own in such landscape, a rather unforgiving place of nothingness except for lingering late afternoon light, a cooling breeze and the chill of solitude and empty moor.

I found the going to the summit of Foel y Geifr to be tough, but thankfully a form of path did exist beside the fence line which strode confidentially up and across the hill.  By the time I reached the summit all I wanted to do was smile and sit down.  This summit has a trig pillar perched at its top with a number of small embedded rocks around its base, one to its north proved the highest and Leica and Trimble data were gathered.

The Leica RX1250 gathering data at the summit of Foel y Geifr

All that remained were two bylchau, the first being that of Trum y Gwragedd and the last being that of Foel Cedig.  The former was Leicaed and Trimbled and the latter just Trimbled.  The first bwlch proved another peat laden affair amongst copious amounts of moor grass and heather, and I joined Alan as the Leica gathered another data set.  As I positioned the Trimble on top of my rucksack to give it elevation above its immediate surrounds the light faded to dusk as the sun cast out from behind cloud beyond Aran Benllyn and the high Aran, giving a dramatic display of late evening light.

The high Aran


The Trimble GeoXH 6000 gathering data at the critical bwlch of Trum y Gwragedd


Last burst of sunlight

Just one survey remained and we stumbled our way down the hill to pinpoint the critical bwlch of Foel Cedig, which proved another heather and bog bound beauty.  From here it was no more than a few minutes plod up to join the high point of the road above Cwm Hirnant where my car awaited, it had been an excellent day on the hill.

 
The last survey of the day, the fourteenth, at the critical bwlch of Foel Cedig


Survey Result:


Foel y Groes

Summit Height:  580.9m (converted to OSGM15)

Summit Grid Reference:  SH 91835 23507

Bwlch Height:  560.5m (converted to OSGM15)

Bwlch Grid Reference:  SH 92028 23791

Drop:  20.4m (500m Sub-Twmpau status confirmed)

Dominance:  3.51% 



 

Moel y Cerrig Duon

Summit Height:  624.3m (converted to OSGM15, Trimble GeoXH 6000) 624.5m (Leica RX1250)

Summit Grid Reference:  SH 92349 24147

Bwlch Height:  545.4m (converted to OSGM15)

Bwlch Grid Reference:  SH 91331 23270

Drop:  79.1m (Leica RX1250 summit and Trimble GeoXH 6000 bwlch)

Dominance:  12.66% (Leica RX1250 summit and Trimble GeoXH 6000 bwlch) 

 



Pt. 605.7m

Summit Height:  605.3m (converted to OSGM15, Trimble GeoXH 6000)  605.7m (Leica RX1250)

Summit Grid Reference:  SH 91857 25730

Bwlch Height:  558.5m (converted to OSGM15, Trimble GeoXH 6000) 558.9m (Leica RX1250)

Bwlch Grid Reference:  SH 92168 26319

Drop:  46.7m (Trimble GeoXH 6000) 46.8m (Leica RX1250)

Dominance:  7.73% (Leica RX1250 summit and bwlch)  





Cefn Coch

Summit Height:  592.6m (converted to OSGM15, Trimble GeoXH 6000) 592.9m (Leica RX1250)

Summit Grid Reference:  SH 92310 26675

Bwlch Height:  561.4m (converted to OSGM15, Trimble GeoXH 6000) 561.7m (Leica RX1250)

Bwlch Grid Reference:  SH 92501 26927

Drop:  31.2m (Trimble GeoXH 6000) 31.3m (Leica RX1250) (Dewey and 500m Twmpau status confirmed)

Dominance:  5.27% (Leica RX1250 summit and bwlch) 

  



Foel y Geifr

Summit Height:  626.0m (converted to OSGM15, Trimble GeoXH 6000) 626.2m (Leica RX1250)

Summit Grid Reference:  SH 93710 27525

Bwlch Height:  514.7m (converted to OSGM15, Trimble GeoXH 6000) 515.0m (Leica RX1250)

Bwlch Grid Reference:  SH 91823 24620

Drop:  111.3m (Trimble GeoXH 6000) 111.2m (Leica RX1250)

Dominance:  17.76% (Leica RX1250 summit and bwlch)



 

Trum y Gwragedd

Summit Height:  611.2m (converted to OSGM15, Leica 530)

Summit Grid Reference:  SH 94114 28400

Bwlch Height:  586.4m (converted to OSGM15, Trimble GeoXH 6000) 586.7m (Leica RX1250)

Bwlch Grid Reference:  SH 93945 27889

Drop:  24.5m (converted to OSGM15, Leica 530 summit and Leica RX1250 bwlch)

Dominance:  4.00% 



 

Foel Cedig

Bwlch Height:  487.4m (converted to OSGM15)

Bwlch Grid Reference:  SH 94458 27324

Drop:  180.0m