Saturday, 11 July 2020

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


Foel Cynfal (SH 749 395) – Dewey deletion

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 Cynfal (SH 749 395)

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 deletion appear below:

The name the hill was listed by in the Deweys is Foel Cynfal, and it is adjoined to the Arenig group of hills which are situated in the central part of North Wales, and it is positioned with the B4391 road to its north, the A470 road to its west and the A4212 road to its south, and has the village of Trawsfynydd towards the south-west.

This hill was not included in the original 1995 Constable publication, with no summit spot height on the publicly available Ordnance Survey maps and with an uppermost 540m ring contour and bwlch contouring between 510m – 520m that appear on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, this hill was noted as an outside possibility for 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 (BLS) of this hill on the 15th July 2000, resulting in 93½ft / 28.5m of drop.  These details were forwarded to the list author; Michael Dewey along with other recent results produced from basic levelling surveys.

Although surveyed as having less than the minimum 30m of drop required to enter this list, the hill was inadvertently included by Michael Dewey.  Its inclusion was subsequently noted during proof reading when an updated copy of the list was received by Myrddyn Phillips.  This hill’s deletion from Dewey status was confirmed in a letter received from the author dated 7th August 2000.  Although its inclusion in this list was an error, it was for a short period of time listed as a Dewey and therefore the details of this hill are appearing in this Hill Reclassification post and the forthcoming Change Register.

The Trimble GeoXH 6000 gathering data at the summit of Foel Cynfal

The Trimble GeoXH 6000 gathering data at the bwlch of Foel Cynfal

As the margin of uncertainty for the BLS method of surveying over terrain such as that on this hill is approximately +/- 2m and as the resulting 28.5m of drop was near the minimum 30m qualifying drop value, this hill was prioritised for a GNSS survey, and this took place on the 1st July 2017.  The summit and bwlch of this hill were surveyed by Myrddyn Phillips and Aled Williams using a Trimble GeoXH 6000, resulting in a 545.5m summit height and a 517.4m bwlch height, with these values giving this hill 28.1m of drop, and confirming its non-Dewey status.


The full details for the hill are:

Name:  Foel Cynfal

OS 1:50,000 map:  124

OS 1:25,000 map:  18

Summit Height:  545.5m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 74998 39546 (Trimble GeoXH 6000)

Bwlch Height:  517.4m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SH 74884 39528 (Trimble GeoXH 6000)

Drop:  28.1m (Trimble GeoXH 6000)


Myrddyn Phillips (July 2020)


Friday, 10 July 2020

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


Ffridd Uchaf (SH 993 500) – Sub-Trichant addition

There has been confirmation of an addition to the list of Y Trichant – The 300m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Ffridd Uchaf (SH 993 500)

The criteria for the list that this addition 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 13th May 2017.

The name the hill is listed by is Ffridd Uchaf and this was derived from the Tithe map, and it is adjoined to the Mynydd Hiraethog group of hills which are situated in the north-eastern part of North Wales (Region A, Sub-Region A2), and it is positioned with the B4501 road to its west and the B5105 road to its south, and has the village of Llanfihangel Glyn Myfyr towards the south.

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list that accompanied the main P30 list, as it was considered not to meet the criteria then used for this sub category. 

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 24m of drop, based on the 375m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger map and the 351m bwlch spot height that appeared at SH 99666 50565 on the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map.

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 addition of this hill to Sub-Trichant status is due to LIDAR analysis, resulting in a 376.4m summit height and a 350.5m bwlch height, with these values giving this hill 25.9m of drop, which is sufficient for it to be classified as a Sub-Trichant.


The full details for the hill are:

Group:  Mynydd Hiraethog

Name:  Ffridd Uchaf

OS 1:50,000 map:  116

Summit Height:  376.4m (LIDAR)

Summit Grid Reference:  SH 99378 50074 (LIDAR)

Bwlch Height:  350.5m (LIDAR)

Bwlch Grid Reference:  SH 99671 50547 (LIDAR)

Drop:  25.9m (LIDAR)


Myrddyn Phillips (July 2020)






Thursday, 9 July 2020

Mapping Mountains – Hill Reclassifications – The Welsh Highlands – Uchafion Cymru


Carreg Gwalch (SH 642 552) – 500m Sub-Uchaf addition

There has been an addition to the listing of The Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data.

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

The Welsh Highlands – Uchafion Cymru This is the revised draft title for the Welsh 500m P15s list that takes in all hills in Wales at or above 500m in height with 15m minimum drop.  Accompanying the main list are three sub lists, these are; 500m Sub-Uchaf, 490m Sub-Uchaf and the Double Sub category, with this hill being added as a 500m Sub-Uchaf.  The criteria for which are all Welsh hills at or above 500m in height with 14m or more and below 15m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams with the Introduction to the list being published on Mapping Mountains in November 2015 and an update relating to the list appearing on Mapping Mountains on the 19th June 2019.

The name the hill is listed by is Carreg Gwalch and it is adjoined to the Yr Wyddfa 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 A4086 road to its north and the A498 to its south-east, and has the village of Capel Curig towards the east north-east.

This hill was not included as a P14 Sub in the original list of Welsh 500m P15s that later became known as Yr Uchafion and latterly as The Welsh Highlands – Uchafion Cymru, as with a 545m summit spot height and bwlch contouring between 530m – 540m that appear on the Ordnance Survey 1:25,000 Explorer map, interpolation suggested that it did not have sufficient drop to be considered for P14 500m Sub-Uchaf status.

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

Since the original compilation of this list there are now a number of interactive maps originated from Ordnance Survey data that are available online.  One of these is available on the Magic Maps website, and it is this map that gives this hill a summit spot height of 546m.

Extract from the Magic Maps website

Another resource now available online is the WalkLakes website which hosts an interactive map originated from the Ordnance Survey Open Data programme.  This map has many spot heights not on other publicly available Ordnance Survey maps and for this hill it also shows a 546m summit spot height which is positioned at SH 64236 55249.

Extract from the WalkLakes website

The details for this hill were also re-assessed when the OS Maps website became available online.  This is the replacement for OS Get-a-map and has contours at 5m intervals which are proving consistently more accurate compared to the 5m contours that sometimes appear on Ordnance Survey 1:25,000 Explorer maps and used to appear on the online Vector Map Local.  This mapping has an uppermost 545m ring contour and bwlch contouring between 530m – 535m, with interpolation giving an estimated bwlch height of c 532m.

Extract from the OS Maps website

Therefore, the addition of Carreg Gwalch to 500m Sub-Uchaf status is due to detail on contemporary maps produced from Ordnance Survey data, resulting in a 546m summit height and an estimated c 532m bwlch height, with these values giving this hill c 14m of drop, which is sufficient for it to be classified as a 500m Sub-Uchaf.


The full details for the hill are:

Group:  Yr Wyddfa

Name:  Carreg Gwalch

OS 1:50,000 map:  115

Summit Height:  546m (spot height)

Summit Grid Reference:  SH 64236 55249 (spot height)

Bwlch Height:  c 532m (interpolation)

Bwlch Grid Reference:  SH 64226 55161 (interpolation) 
  
Drop:  c 14m (spot height summit and interpolated bwlch) 


For the additions, deletions and reclassifications to The Welsh Highlands – Uchafion Cymru reported on Mapping Mountains please consult the following Change Registers:










Aled Williams and Myrddyn Phillips (July 2020)



Wednesday, 8 July 2020

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


Moel y Gyrafolen (SH 672 352) – 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.

Moel y Gyrafolen (SH 672 352)

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 Moel y Gyrafolen, and it is adjoined to the Rhinogydd group of hills which are situated in the north-western part of Wales, and it is positioned with the A496 road to its west and the A470 road to its east, and has the village of Trawsfynydd towards the east.

This hill was not included in the original 1995 Constable publication, but with a 535m summit spot height and bwlch contouring between 500m – 510m that appear on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, this hill was noted as an outside possibility for 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 (BLS) of this hill on the 23rd July 2000, resulting in 100ft / 30.5m 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.

As the margin of uncertainty for the BLS method of surveying over terrain such as that on Moel y Gyrafolen is approximately +/- 1.5m and as the resulting 30.5m of drop was near the minimum 30m qualifying drop value, this hill was prioritised for a GNSS survey, and this took place on the 22nd February 2013.  The summit and bwlch of this hill were surveyed by John Barnard, Graham Jackson and Myrddyn Phillips using a Leica GS15.

Surveying for summit position on Moel y Gyrafolen

The Leica GS15 set-up position at the bwlch of Moel y Gyrafolen

The survey resulted in a 536.8m summit height and a 506.7m bwlch height, with these values giving this hill 30.1m of drop, and confirming its Dewey status.
 

The full details for the hill are:

Name:  Moel y Gyrafolen

OS 1:50,000 map:  124

OS 1:25,000 map:  18

Summit Height:  536.8m (converted to OSGM15, Leica GS15)

Summit Grid Reference:  SH 67218 35292 (Leica GS15)

Bwlch Height:  506.7m (converted to OSGM15, Leica GS15)

Bwlch Grid Reference:  SH 67066 35195 (Leica GS15)

Drop:  30.1m (Leica GS15)


Myrddyn Phillips (July 2020)






Tuesday, 7 July 2020

Mapping Mountains – Hill Reclassifications – 30-99m Twmpau and 100m Twmpau


The Knoll (ST 424 904) – 30-99m Twmpau reclassified to 100m Twmpau

There has been a reclassification to the list of 30-99m Twmpau and 100m Twmpau, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of The Knoll (ST 424 904)

The criteria for the two listings 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.

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m 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 name the hill is listed by is The Knoll, and it is adjoined to the Gwent Is Coed group of hills which are situated in the south-eastern part of South Wales (Region C, Sub-Region C3), and it is positioned with the A48 road to its north and the M4 motorway to its south, and has the city of Casnewydd (Newport) towards the west south-west.

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 main P30 list and listed with a c 90m summit height, based on its uppermost contour that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer 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-assessed and it was listed with c 51m of drop, based on an estimated c 94m summit height based on interpolation of 5m contouring and a 43m bwlch spot height that appears on 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. 

LIDAR close-up image of The Knoll

Therefore, the reclassification of this hill from 30-99m Twmpau to 100m Twmpau status is due to LIDAR analysis, resulting in a 101.9m summit height and a 43.1m bwlch height, with these values giving this hill 58.7m of drop and 57.66% dominance.  With the summit height of this hill sufficient for it now to be classified as a 100m Twmpau.


The full details for the hill are:

Group:  Gwent Is Coed

Name:  The Knoll

OS 1:50,000 map:  171, 172

Summit Height:  101.9m (LIDAR)

Summit Grid Reference:  ST 42467 90424 (LIDAR)

Bwlch Height:  43.1m (LIDAR)

Bwlch Grid Reference:  ST 42135 90345 (LIDAR)

Drop:  58.7m (LIDAR)


Myrddyn Phillips (July 2020)