Sunday, 2 October 2022

Mapping Mountains – Summit Relocations – 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales


Black Acre (SN 292 146) 

There has been a Summit Relocation 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 Black Acre (SN 292 146)

The criteria for the two listings that this summit relocation 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

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.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3rd 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 Black Acre and this was derived from the Tithe map, and it is adjoined to the Mynydd Pencarreg group of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned with the A40 road to its north, the A4066 road to its west and a minor road to its east, and has the small town of Sanclêr (St Clears) towards the north-west.

When the original Welsh 30-99m P30 list was published on Geoff Crowder’s v-g.me website, this hill was listed with a summit height of c 60m, which is the uppermost Ordnance Survey map ring contour that appears on the 1:25,000 Explorer map. 

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.

LIDAR analysis gives ground on a raised field boundary as the highest on this hill, however protocols dictate that as this is deemed a relatively recent man-made construct such ground is discounted from the height of a hill. 

LIDAR summit image of Black Acre (SN 292 146)

The height produced by LIDAR analysis to the natural summit of this hill is 61.3m positioned at SN 29283 14648, and this position in relation to the raised field boundary comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies to when the high point is positioned in a different field, to a different feature such as a conifer plantation, within a different map contour, a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is considered a relatively recent man-made construct, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist.

Therefore, the summit height produced by LIDAR analysis is 61.3m and this is to the natural summit of the hill which is positioned at SN 29283 14648, this position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and is approximately 20 metres south-eastward from where the high point of the raised field boundary is positioned. 

 

The full details for the hill are: 

Group:  Mynydd Pencarreg 

Name:  Black Acre 

OS 1:50,000 map:  159

Summit Height:  61.3m (LIDAR) 

Summit Grid Reference (New Position):  SN 29283 14648 (LIDAR) 

Bwlch Height:  29.6m (LIDAR) 

Bwlch Grid Reference:  SN 29308 15527 (LIDAR) 

Drop:  31.8m (LIDAR) 

Dominance:  51.80% (LIDAR) 

 

Myrddyn Phillips (October 2022)

 

  

Saturday, 1 October 2022

Y Trichant - The 300m Hills of Wales

 

Y Trichant - The 300m Hills of Wales

The most comprehensive and accurate listing to this height band of hills ever published 

 

Introduction 

Visiting the 300m hills of Wales can take you on a journey the length and breadth of the country with all major hill ranges represented.  This height band is the metric equivalent of the imperial 1,000ft and this list produces a challenge on par with many other lists of higher hills. 

The hills within this list take in a variety of upland landscape, including land that can be considered as Mynydd; mountain and moor, and Ffridd; heath, grassland, woodland and high pasture. 

The Welsh aspect of these hills is represented in their combined title; Y Trichant; when translated in to English, this is the three hundred, with the full title being Y Trichant – The 300m Hills of Wales, and this listing is the most comprehensive and accurate to this height band of hills ever published.


 

The List:  The listing of the Y Trichant- The 300m Hills of Wales takes in all 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.

 

Publication History:  This list was first published on 22nd October 2004 on Geoff Crowder’s v-g.me website and entitled The Welsh 300 Metre Peaks, coinciding with Geoff’s publication the list was also published by Mike Grant on his 5everdene website.

The next publication of the list was in January 2005 on the RHB Yahoo Group file database, with the file later updated in January 2006 and entitled 300-499 Man Eng Wales.  This file was uploaded by Rob Woodall who then augmented data from E D ‘Clem’ Clements into the database.

It was the publication on the RHB Yahoo Group file database that was later duplicated en masse by Mark Jackson without consultation with the author, with these data forming the equivalent part of the Tumps.  This has resulted in years of undue data divergence that is ongoing.

 

Maintaining the List:  The master list for the above publications was hand written and this was used for a number of years to then update with any additional information.  The list is now maintained in spreadsheet format, with all necessary information appearing in the Mapping Mountains publication.  Between the first publication of this list and its latest publication on Mapping Mountains it has undergone a number of significant updates and the timeframe for these are given below.

 

Significant Updates: 

2004:  The original list did not use interpolation for estimated heights and therefore accepted Ordnance Survey spot heights as fact.  With the accompanying Hills to be surveyed P20 sub list only including hills that once surveyed stood a chance of entering the main P30 list.

2005:  Drop values added with interpolated heights used and the accompanying sub list standardised.

2012:  The original list relied upon paper mapping with the newly published Ordnance Survey 1:25,000 Explorer maps prioritised over the 1:50,000 Landranger.  The advent of online mapping included the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and enabled a full review of all data in this list.  The updating of this list using information on this mapping formed a part of the compilation of The Welsh P15s with all 300m Welsh hills being listed down to P14, resulting in a comprehensive list to the Welsh 300m P20s.

2013:  Numerical accuracy within hill lists has dramatically increased compared to when Ordnance Survey paper mapping was the tool of reference.  This increased accuracy is due to the advent of independent surveyors using survey grade GNSS equipment and for this list it is the use of the Trimble GeoXH 6000 that has greatly benefited the numerical data within it, with the first 300m Welsh hill surveyed with this equipment in December 2013 and with these surveys ongoing to the present day.

2017:  In May 2017 an article was published on Mapping Mountains giving an introduction to this list and its renaming to; Y Trichant – The 300m Hills of Wales and mentioning future intention to publish the list in its entirety.

2018:  The use of the LIDAR (Light Detection & Ranging) technique has revolutionised hill listings resulting in a plethora of reclassifications.  My use of LIDAR started in March 2018 and is ongoing, with this list heavily dependent upon the accuracy produced from LIDAR analysis.

2022:  The Mapping Mountains publication of Y Trichant – The 300m Hills of Wales commences on the 1st January.  

 

Major Advances:  Although the criteria has remained the same the list has changed greatly since its first publication, with the advent of independent surveyors and the use of LIDAR enabling greater numerical accuracy.

Place name research within hill lists has also made dramatic progress since the first publication of this list, with local enquiry and historical research enabling greater depth and understanding for the hill names used.

Since the advent of Mapping Mountains in November 2013 all status changes to this list are documented in Hill Reclassification posts on this site, with all major significant amendments also documented.

 

Mapping Mountains Publication:  For the Mapping Mountains publication of the Y Trichant – The 300m Hills of Wales the list has been fully re-evaluated using GNSS results produced via Trimble GeoXH 6000 and Leica surveys, available LIDAR and the latest online mapping.  Each hill name has been considered for its most appropriate use with Ordnance Survey historical and contemporary mapping and the Tithe map used in conjunction with any local enquiry.  The accompanying sub list entitled the Sub-Trichant is the first standardised P20 sub list to this height band of hills to ever be published.

 

Y Trichant – The 300m Hills of Wales as a downloadable list in Google Doc format 

 

The Mapping Mountains list consists of the following:

 

Name:  This is considered the most appropriate name for the hill, based on local usage where this is known.  The name used does not always correspond to contemporary Ordnance Survey map spelling and/or composition or the name may not appear on any Ordnance Survey map.  Where an appropriate name is not forthcoming for the hill, the Point (for example; Pt. 343.1m) notation is used rather than making up a name that has no local or historical evidence of use.

 

Summit Height (m):  This gives the map height in metres of the hill above Ordnance Datum Newlyn (ODN), often referred to as sea level.  Where a height is quoted to a decimal place it implies that the hill has been surveyed by GNSS receiver (survey grade GPS) or obtained from LIDAR analysis (these heights may not match current Ordnance Survey map heights), with the heights produced by GNSS receiver converted to OSGM15.  Where a ‘c’ (circa) appears preceding the height it means there is no known spot height available and the height has been estimated from contour interpolation.

 

1:50,000 Map:  This column gives the number or numbers of the 1:50,000 Ordnance Survey Landranger map that the summit of the hill appears on.

 

1:25,000 Map:  This column gives the number or numbers of the 1:25,000 Ordnance Survey Explorer map that the summit of the hill appears on.

 

Summit Grid Reference:  This is the ten figure grid reference for the summit of the hill.  This has either been produced by an accurate survey via GNSS receiver or LIDAR analysis, a map spot height, hand-held GPS via DoBIH or for interpolated heights by a centralised position in an uppermost contour ring.

 

Summit Grid Reference extracted from:  Details of where the ten figure grid reference for the summit was derived.

 

Drop (m):  This column details the prominence of the hill, otherwise known as drop or re-ascent.  The drop is the height difference between the summit and the lowest connecting bwlch to the higher parent peak along the watershed.  The letter ‘c’ before the drop figure signifies there is no spot height or surveyed height known for either summit or more usually, the bwlch, therefore a part of the drop figure has been estimated from contour interpolation.

 

Bwlch Grid Reference:  This is the ten figure grid reference for the bwlch of the hill.  This has either been produced by an accurate survey via GNSS receiver or LIDAR analysis, a map spot height, hand-held GPS via DoBIH or when none of the above is available by a centralised position between converging hill to hill and valley to valley contours.

 

Bwlch Grid Reference extracted from:  Details of where the ten figure grid reference for the bwlch was derived.

 

Bwlch Height (m):  This gives the map height in metres of the bwlch of the hill above Ordnance Datum Newlyn (ODN), often referred to as sea level.  Where a height is quoted to a decimal place it implies that the bwlch has been surveyed by GNSS receiver (survey grade GPS) or obtained from LIDAR analysis (these heights may not match current Ordnance Survey map heights), with the heights produced by GNSS receiver converted to OSGM15.  Where a ‘c’ (circa) appears preceding the height it means there is no known spot height available and the height has been estimated from contour interpolation.

 

Notes:  This column gives additional information relating to the hill, including headings for Place Name Information, Numerical Data and Listing History.

 

Myrddyn Phillips (January 2022)

 

 

Access:  This is a collection of Welsh hills that meet set criteria and although such a list can be a reference for people to visit the hills, for those wishing to do so they should abide by any legal restriction and if unsure of permissible access ask permission to visit from the respective landowner.

 

Risks:  Hill walking is an activity with risks and dangers, both natural and man-made.  You should not attempt hills beyond your capabilities, and should fully appraise yourself of, and prepare for, the possible risks before attempting to visit any hill.  Participants in these activities should be aware of and accept these risks, and be responsible for their own actions and involvement.

 

Thanks:  With special thanks to Aled Williams for his continued support, Mark Trengove for advice over many years, Geoff Crowder and Mike Grant for past publication and Rob Woodall who inputted data for the list published on the RHB Yahoo Group file database, and to the people who submit 10 figure grid references to the Database of British and Irish Hills (DoBIH) and for DoBIH making these available for public use.

 

This list will appear in instalments published at 7.00pm on the 1st and 15th of each month, with the nineteenth instalment to the Tarren y Gesail group of hills.  The Carnedd Wen group of hills will appear on the 15th October. 

 

Y Trichant –The 300m Hills of Wales as a downloadable list in Google Doc format     

Mapping Mountains – Significant Height Revisions – Y Trichant – The 300m Hills of Wales

 

Celynnog Hill (SO 051 971) 

There has been a Significant Height Revision to a hill that is listed in the Y Trichant – The 300m Hills of Wales, 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 Celynnog Hill (SO 051 971)

The criteria for the list that this height revision 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, and the Introduction to the Mapping Mountains publication of the list appearing on the 1st January 2022. 

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

The name the hill is listed by is Celynnog Hill, and it is adjoined to the Carnedd Wen group of hills, which are situated in the southern part of North Wales (Region A, Sub-Region A3), and it is positioned with minor roads to its north-east, north-west and south-east, and has the village of Caersŵs towards the south south-west.

When the original 300m 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 with a summit height of 369m, based on the spot height 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

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 Celynnog Hill (SO 051 971)

LIDAR analysis gives the summit height of this hill as 370.4m 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 summit 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 370.4m and this was derived from LIDAR analysis, this is 1.4m higher than the previously listed summit height of 369m which appears as a spot height on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

 

The full details for the hill are: 

Group:  Carnedd Wen 

Name:  Celynnog Hill 

OS 1:50,000 map:  136

Summit Height (New Height):  370.4m (LIDAR)                                                           

Summit Grid Reference:  SO 05129 97189 (LIDAR) 

Bwlch Height:  330.4m (LIDAR) 

Bwlch Grid Reference:  SO 04838 97119 (LIDAR) 

Drop:  40.1m (LIDAR) 

 

Myrddyn Phillips (October 2022)

 

 

 

 

 

 

 

Friday, 30 September 2022

Mapping Mountains – Significant Name Changes – The Fours - The 400m Hills of England

 

The Fours - The 400m Hills of England – Significant Name Changes

The Fours are the English hills at and above 400m and below 500m in height that have a minimum drop of 30m.  Accompanying the main P30 list are three sub lists; these are the 400m Sub-Four390m Sub-Four and 390m Double Sub-Four category’s, with their criteria detailed in the respective Change Registers that are linked in their above titles, with the Introduction to this list being published on Mapping Mountains on the 22nd December 2013.

The list is co-authored by Myrddyn Phillips and Aled Williams and the posts that have appeared on Mapping Mountains detailing the significant name changes to the main P30 list and the sub lists appear below presented chronologically in receding order.









Mapping Mountains - Significant Name Changes - The Fours - The 400m Hills of England

Long Crags (NT 955 214) - 36th significant name change

Hill Reclassifications post for Long Crags

Significant Height Revisions post for Long Crags

Summit Relocations post for Long Crags

 

There has been a Significant Name Change to a hill that is listed in the The Fours – The 400m Hills of England, with the summit height, col height and their locations, the drop and status of the hill derived by Joe Nuttall who produceda summit analysis programme using LIDAR, and then by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Long Crags (NT 955 214) and Broad Moss (NT 956 210)

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

The Fours – The 400m Hills of England.  English hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main listing of The Fours are three categories of sub hills, with this hill being included in the 400m Sub-Four category, the criteria for which are all English hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and the 2nd edition of the booklet containing this list was published by Mapping Mountains Publications on the 24th April 2018.

The Fours - The 400m Hills of England by Myrddyn Phillips and Aled Williams

The hill is adjoined to the The Cheviot group of hills, which are situated in Northumberland (Region 33: Scottish Border to the River Tyne), and it is positioned with a minor road to its north and the A697 road to its east, and has the town of Wooler towards the north north-east.

When the 2nd edition of the The Fours – The 400m Hills of England was published by Mapping Mountains Publications in April 2018, this hill was not included in the accompanying sub list, as it was considered not to meet the criteria used for this sub category.

However, during the updating of this list for the 2nd edition this hill was noted and listed as Broad Moss with 18m of drop, based on the 432m summit spot height positioned at NT 95699 21058 that appears on the Ordnance Survey 1:50,000 Lanranger and 1:25,000 Explorer map and the 414m col spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

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.

LIDAR analysis gives the higher summit to Long Crags positioned at NT 95597 21432, therefore this is a significant name change based on the qualifying summit having been relocated from the originally listed summit of Broad Moss.

Therefore, the name this hill is now listed by in The Fours - The 400m Hills of England is Long Crags and this was instigated from a summit relocation. 

 

The full details for the hill are:

Group:  The Cheviot

Name:  Long Crags

Previously Listed Name:  Broad Moss 

OS 1:50,000 map:  74, 75

Summit Height:  439.5m (LIDAR)

Summit Grid Reference:  NT 95597 21432 (LIDAR)

Col Height:  415.8m (LIDAR)

Col Grid Reference:  NT 95503 20955 (LIDAR)

Drop:  23.7m (LIDAR)

 

Our thanks to Ronnie Bowron for bringing the details of this hill to our attention

Myrddyn Phillips and Aled Williams (September 2022)