Mapping Mountains – Hill Reclassifications – Y Trichant – The 300m Hills of Wales and 200m Twmpau

 

Cefn Coch (SN 747 962) – Sub-Trichant reclassified to 200m Sub-Twmpau

There has been a reclassification to the list of Y Trichant – The 300m Hills of Wales and the 200m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Cefn Coch (SN 747 962)

The criteria for the two listings that this reclassification applies to are:

Y Trichant – The 300m Hills of Wales – Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant, with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13^th May 2017, and the Introduction to the Mapping Mountains publication of the list appearing on the 1^st January 2022. 

Y Trichant - The 300m Hills of Wales by Myrddyn Phillips

200m Twmpau – Welsh hills at or above 200m and below 300m in height that have 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m 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 200m Twmpau by Myrddyn Phillips

The name the hill is listed by is Cefn Coch, and it is adjoined to the Banc Llechwedd Mawr group of hills which are situated in the northern part of South Wales (Region B, Sub-Region B1), and it is positioned with the A487 road to its west and a minor roads to its east, and has the town of Machynlleth towards the north.

When the original 300m height band of Welsh P30 hills was published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list with an estimated summit height of c 300m based on interpolation of the uppermost ring contour that appears on the Ordnance Survey 1:25,000 Explorer map, with an accompanying note stating; Three points of same height, indicating three separate 300m ring contours. 

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

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 is due to LIDAR analysis, resulting in 24.6m of drop, with a 299.7m summit height and a 275.1m bwlch height.  Therefore, as the summit height is insufficient for Sub-Trichant status the hill is reclassified to a 200m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Banc Llechwedd Mawr 

Name:  Cefn Coch 

OS 1:50,000 map:  135

Summit Height:  299.7m (LIDAR)                                                           

Summit Grid Reference:  SN 74725 96284 (LIDAR) 

Bwlch Height:  275.1m (LIDAR) 

Bwlch Grid Reference:  SN 75003 95681 (LIDAR) 

Drop:  24.6m (LIDAR) 

 

Myrddyn Phillips (December 2022)

 

 

 

 

 

 

Mapping Mountains – Significant Name Changes – 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales

 

Cefn Coch (SH 610 396) 

There has been a Significant Name Change to a hill that is listed in the 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Cefn Coch (SH 610 396)

The criteria for the two listings that this name change applies to are: 

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m 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 30-99m Twmpau by Myrddyn Phillips

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height, with the Introduction to the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format. 

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The hill is adjoined to the Moelwynion group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A498 road and the B4410 road to its north-west, the A497 road and the A487 road to its south-west and the A4085 road to its east, and has the town of Penrhyndeudraeth towards the south. 

The hill appeared in the original 30-99m Welsh P30 list on Geoff Crowder’s v-g.me website under the invented and transposed name of Bryn Ty-fry, with an accompanying note stating; Name from house to the West.

Bryn Ty-fry

81m

SH611396

124

18

86m on 1984 1:50000 map. Name from house to the West

 

During my early hill listing I thought it appropriate to either invent a name for a hill, or use a name that appeared near to the summit of the hill on Ordnance Survey maps of the day.  My preference was to use farm names and put Pen, Bryn or Moel in front of them.  This is not a practice that I now advocate as with time and inclination place-name data can be improved either by asking local people or by examining historic documents, through this form of research an appropriate name for the hill can usually be found.  

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

Since publication of these P30 lists on Geoff Crowder’s v-g.me website 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 Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map, and the interactive mapping on the Magic Maps and WalkLakes websites.  One of the historic maps now available online is the Ordnance Survey One-Inch ‘Old Series’ map and it is detail on this map that forms the basis for the change in the listed name of this hill. 

Extract from the Ordnance Survey One-Inch 'Old Series' map

The One-Inch ‘Old Series’ map was the first map that Ordnance Survey had published and this culminated from the whole of Britain being surveyed between 1791 and 1874 and the detail gathered therein produced at a scale of one inch to the mile and published in sheet format between 1805 and 1874.  The One-Inch ‘Old Series’ maps for the whole of Wales are now available online; they are also available in map format as enlarged and re-projected versions to match the scale and dimensions of the Ordnance Survey 1:50,000 Landranger series and are published by Cassini.  This series of maps form another important part in the study of Welsh upland place-names and bridge the time frame leading up to the production of the Ordnance Survey base map of the Six-Inch series, and importantly for this hill and its listed name, it is this map that has the name of Cefn Coch adjacent to this hill. 

Therefore, the name this hill is now listed by in the 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales is Cefn Coch and this was derived from the Ordnance Survey One-Inch ‘Old Series’ map.

 

The full details for the hill are: 

Group:  Moelwynion 

Name:  Cefn Coch

Previously Listed Name:  Bryn Ty-fry 

OS 1:50,000 map:  124

Summit Height:  86.6m (LIDAR) 

Summit Grid Reference:  SH 61030 39620 (LIDAR)               

Bwlch Height:  51.5m (LIDAR) 

Bwlch Grid Reference:  SH 61461 39763 (LIDAR) 

Drop:  35.1m (LIDAR) 

Dominance:  40.51% (LIDAR) 

 

Myrddyn Phillips (December 2021)

 

 

 

 

Mapping Mountains – Significant Height Revisions – 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales

 

Cefn Coch (SH 610 396) 

There has been a Significant Height Revision to a hill that is listed in the 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Cefn Coch (SH 610 396)

The criteria for the two listings that this height revision applies to are:

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m 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 30-99m Twmpau by Myrddyn Phillips

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height, with the Introduction to the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format. 

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is now listed by is Cefn Coch and it is adjoined to the Moelwynion group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A498 road and the B4410 road to its north-west, the A497 road and the A487 road to its south-west and the A4085 road to its east, and has the town of Penrhyndeudraeth towards the south. 

When the original 30-99m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the P30 category, and it was listed with an 81m summit height, with an accompanying note stating; 86m on 1984 1:50,000 map. 

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with 33m of drop and 40.74% dominance, based on the 81m summit spot height and the 48m bwlch spot height that appear on the Ordnance Survey 1:25,000 Explorer map. 

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

The details for this hill were subsequently re-assessed as the bwlch contouring on the Ordnance Survey 1:25,000 Explorer map is between 50m – 60m, therefore according to map contouring the 48m spot height is below the position of the bwlch.  This reassessment resulted in the hill being listed with an estimated c 26m of drop, based on the 81m summit spot height and an estimated c 55m bwlch height. 

The details for this hill were later reassessed and the 86m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger map was favoured over that of the 81m spot height, and with the bwlch height amended to an estimated c 54m, these values gave this hill an estimated c 32m of drop and 37.21% dominance. 

Extract from the Ordnance Survey 1:50,000 Landranger map

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 summit image of Cefn Coch (SH 610 396)

The summit height produced by LIDAR analysis is 86.6m and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are: 

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

Therefore, the new listed summit height of this hill is 86.6m and this was derived from LIDAR analysis, this is 5.6m higher than the originally listed summit height of 81m which appears as a spot height on the Ordnance Survey 1:25,000 Explorer maps.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Moelwynion 

Name:  Cefn Coch 

OS 1:50,000 map:  124

Summit Height (New Height):  86.6m (LIDAR) 

Summit Grid Reference:  SH 61030 39620 (LIDAR)               

Bwlch Height:  51.5m (LIDAR) 

Bwlch Grid Reference:  SH 61461 39763 (LIDAR) 

Drop:  35.1m (LIDAR) 

Dominance:  40.51% (LIDAR) 

 

Myrddyn Phillips (December 2021)

 

 

 

Mapping Mountains – Hill Reclassifications – 30-99m Twmpau

Cefn Coch (SH 610 396) – 30-99m Sub-Twmpau reclassified to 30-99m Twmpau 

There has been confirmation of a reclassification to the list of 30-99m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Cefn Coch (SH 610 396)

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

30-99m Twmpau – Welsh hills at or above 30m and below 100m in height that have 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m 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 30-99m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Cefn Coch and it is adjoined to the Moelwynion group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A498 road and the B4410 road to its north-west, the A497 road and the A487 road to its south-west and the A4085 road to its east, and has the town of Penrhyndeudraeth towards the south. 

When the original 30-99m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the P30 category.  This hill was listed with an 81m summit height, with an accompanying note stating; 86m on 1984 1:50,000 map. 

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

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with 33m of drop, based on the 81m summit spot height and the 48m bwlch spot height that appear on the Ordnance Survey 1:25,000 Explorer map. 

The details for this hill were subsequently re-assessed as the bwlch contouring on the Ordnance Survey 1:25,000 Explorer map is between 50m – 60m, therefore according to map contouring the 48m spot height is below the position of the bwlch.  This reassessment resulted in the hill being listed with an estimated c 26m of drop, based on the 81m summit spot height and an estimated c 55m bwlch height. 

The details for this hill were later reassessed and the 86m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger map was favoured over that of the 81m spot height, and with the bwlch height amended to an estimated c 54m, these values gave this hill an estimated c 32m of drop. 

Extract from the Ordnance Survey 1:50,000 Landranger map

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 confirmation of the reclassification of this hill from 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in an 86.6m summit height and a 51.5m bwlch height, with these values giving this hill 35.1m of drop, which is sufficient for it to be classified as a 30-99m Twmpau. 

 

The full details for the hill are: 

Group:  Moelwynion 

Name:  Cefn Coch 

OS 1:50,000 map:  124

Summit Height:  86.6m (LIDAR) 

Summit Grid Reference:  SH 61030 39620 (LIDAR)               

Bwlch Height:  51.5m (LIDAR) 

Bwlch Grid Reference:  SH 61461 39763 (LIDAR) 

Drop:  35.1m (LIDAR) 

 

Myrddyn Phillips (December 2021)

 

 

  

Mapping Mountains – Trimble Surveys – Moelwyn Mawr

 

22.09.21  Cefn Coch (SH 610 396) 

LIDAR image of Cefn Coch (SH 610 396)

Sometimes a walk can take on a surreal aspect where one part is in utter contrast to another.  This hill was such an example.  Cefn Coch; with the name appearing on the Ordnance Survey One-Inch ‘Old Series’ map, is positioned above the town of Penrhyndeudraeth and is one of many similar hills in this area that qualify for P30 status that are both wooded, rocky and seemingly pathless. 

We had hoped to visit Moel y Dyniewyd (SH 612 477), but low cloud and rain meant our plans were quickly rearranged.  The weather conditions dictated lower summits and Aled suggested visiting three hills, with Cefn Coch the second, all of them wooded, which would at least shelter us from any continuing drizzled rain.  However, this also meant that I had not come prepared with the ten figure grid references for each hill. 

Moel y Dyniewyd (SH 612 477)

We approached Cefn Coch from the east having parked in a large lay-bi on the A4085 road just below its connecting bwlch.  We walked up the road to where a public footpath sign confidently pointed toward the direction of the hill.  This we followed and then started to gain height giving views across Traeth Mawr to the higher Eryri peaks. 

The Yr Wyddfa massif was still cloaked in cloud as were the higher Moelwynion, but Cnicht stared back at us, standing out with its shapely profile easily identified.  Across the intervening flatlands Moel Ddu stood out with a cloud enshrouded Moel Hebog beyond.  From where we now were this view was to be savoured and more so as earlier in the morning the gloom was almost down to road level. 

The view of the Yr Wyddfa massif before the brambles overwelmed us!

This view was at contrast to what we found the higher up the hill we went.  Online logs gave a foretaste of the undergrowth encountered, with numerous visits finding a pathless morass of brambles. 

I followed Aled as he negotiated a way upward, initially a path of sorts made its way through bracken, but this soon lost interest and disappeared when the first brambles made their entrance.  Soon afterward we encountered a wall which was easily negotiated.  On the other side more bracken and brambles led to a rock outcrop which we slithered up and over.  More brambles emerged beyond! 

We reached a point that could have been the summit, but before setting the Trimble up, Aled investigated farther on and soon called me to join him as he was standing on higher ground.  Not satisfied with this position he again investigated farther in to the mass of undergrowth and reached a point that looked as if it was the summit.  Without a ten figure grid reference for the high point we were unaware that we were still 100 metres or so from the true summit.  By now my legs had been torn to pieces with bloodied scratches making a patchwork of patterns. 

The point we were now at consisted of a large mossed rock and soon the Trimble was set up gathering data.  During data collection we sat below the equipment and debated the fineries of what constitutes a published hill list.  This subject has direct relevance to a project we are currently working on, so time now permitted that we could discuss the details at length. 

Gathering data at the point we thought the summit

Once allotted data were gathered and stored I closed the equipment down, packed it away and followed Aled through the jungle of brambles and down the slithery rock to finally emerge back on the public footpath.  It was only a short walk from here to the awaiting car. 

Back through the jungle of brambles

When back home I processed the data and checked the co-ordinates against those on the Hill Bagging website and from LIDAR analysis.  Once data were processed it was obvious that the Trimble data set was not good, which was not a surprise considering the enclosed nature of where it was taken from, therefore this will not be used.  The co-ordinates confirmed we were approximately 100 metres from the high point of the hill.  Hopefully a repeat ascent in winter to the true summit will give my legs a chance to survive the experience, when wearing trousers instead of shorts will protect them from being scratched and bloodied as they had been today. 

 

Survey Result: 

 

Cefn Coch (significant name change)

Summit Height:  86.6m (LIDAR) (significant height revision)

Summit Grid Reference:  SH 61030 39620 (LIDAR)

Bwlch Height:  51.5m (LIDAR)

Bwlch Grid Reference:  SH 61461 39763 (LIDAR)

Drop:  35.1m (LIDAR) (30-99m Sub-Twmpau reclassified to 30-99m Twmpau)

Dominance:  40.51% (LIDAR)

 

 

For further details please consult the Trimble Survey Spreadsheet