Wednesday 31 July 2019

Mapping Mountains – Hill Reclassifications – Y Trichant


Llanbradach Tip (ST 138 913) – Sub-Trichant addition

There has been an addition of a hill to the Y Trichant list, 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 Llanbradach Tip (ST 138 913)

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

Y Trichant – 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 this hill is listed by is Llanbradach Tip and as its name implies the hill is the result of mine spoil and it is the western of three pyramidal tips, and it is adjoined to the Cymoedd Gwent group of hills, which are situated in the eastern part of South Wales (Region C, Sub-Region C2), and is positioned with the B4263 road to its south-west and the A469 road and the Afon Rhymni (Rhymney River) to its east, and has the small community of Llanbradach towards its south-east.

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 as it was thought not to meet the criteria then used; however this sub list has now been standardised and interpolated heights and drop values also included in the main P30 and the accompanying sub list.

When this list was standardised and interpolated heights also included the area surrounding this hill was re-assessed but as the Ordnance Survey 1:25,000 Explorer map shows the hill to have no contours and the 1:50,000 Landranger map shows the hill with two ring contours its drop value was difficult to estimate.

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

The addition of this hill to Sub-Trichant status is due to LIDAR analysis, resulting in a 331.3m summit height and a 310.4m bwlch height, with these values giving this hill 20.9m of drop which is sufficient for it to be classified as a Sub-Trichant.

 
The full details for the hill are:

Group:  Cymoedd Gwent

Name:  Llanbradach Tip

OS 1:50,000 map:  171

Summit Height:  331.3m (LIDAR)

Summit Grid Reference:  ST 13843 91345 (LIDAR)

Bwlch Height:  310.4m (LIDAR)

Bwlch Grid Reference:  ST 13784 91419 (LIDAR)
 
Drop:  20.9m (LIDAR)


Myrddyn Phillips (July 2019)




Tuesday 30 July 2019

Mapping Mountains – Significant Height Revisions – Yr Uchafion


Pt. 690.2m (SH 647 468)

There has been a Significant Height Revision to a hill that is listed in the Yr Uchafion, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips on the 23rd March 2019.

Pt. 690.2m (SH 647 468)

The criteria for the listing that this significant height revision applies to are:

Yr Uchafion – Welsh hills at or above 500m in height that have 15m minimum drop.  The list is co-authored by Myrddyn Phillips and Aled Williams, with the Introduction to this list appearing on Mapping Mountains on the 4th November 2015.

The hill is currently listed by the point (Pt. 690.2m) notation and it is adjoined to the Moelwynion range of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A4085 road to its south-west, the A498 road to its north-west and the A470 road towards the east, and has the small community of Croesor towards the south-west and the town of Blaenau Ffestiniog towards the east.

Prior to the survey with the Trimble GeoXH 6000 this hill was listed with a 688m summit height which appears as a spot height 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 Vector Map Local hosted on the Geograph website

The summit height produced by the Trimble GeoXH 6000 survey is 690.2m, this is not a substantial height revision when compared to some revised heights, but it does come 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 any other GNSS receiver, 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.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 Explorer map is being prioritised in favour of the 1:50,000 Landranger map for detailing these revisions.

The Trimble GeoXH 6000 gathering data at the summit of Pt. 690.2m (SH 647 468)

Therefore, the new summit height of this hill is 690.2m and this was produced by surveying with the Trimble GeoXH 6000, this is 2.2m higher than its previously listed height of 688m which appears as a spot height on the Ordnance Survey Vector Map Local hosted on the Geograph website, however this new height is in accordance with the 5m contouring on OS Maps.

Extract from the OS Maps website


ills of Wales, and are reproduced below@
The full details for the hill are:

Group:  Moelwynion

Name:  Pt. 690.2m

OS 1:50,000 map:  115

Summit Height (New height):  690.2m (converted to OSGM15)

Summit Grid Reference:  SH 64799 46864
  
Bwlch Height:  670.9m (converted to OSGM15)

Bwlch Grid Reference:  SH 64681 46742

Drop:  19.3m



Myrddyn Phillips and Aled Williams (July 2019)



Monday 29 July 2019

Mapping Mountains – Hill Reclassifications – Y Trichant


Llanbradach Tip (ST 139 913) – Sub-Trichant addition

There has been an addition of a hill to the Y Trichant list, 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 Llanbradach Tip (ST 139 913)

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

Y Trichant – 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 this hill is listed by is Llanbradach Tip and as its name implies the hill is the result of mine spoil and it is the central of three pyramidal tips, and it is adjoined to the Cymoedd Gwent group of hills, which are situated in the eastern part of South Wales (Region C, Sub-Region C2), and is positioned with the B4263 road to its south-west and the A469 road and the Afon Rhymni (Rhymney River) to its east, and has the small community of Llanbradach towards its south-east.

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 as it was thought not to meet the criteria then used; however this sub list has now been standardised and interpolated heights and drop values also included in the main P30 and the accompanying sub list.

When this list was standardised and interpolated heights also included the area surrounding this hill was re-assessed but as the Ordnance Survey 1:25,000 Explorer map shows the hill to have no contours and the 1:50,000 Landranger map shows the hill with two ring contours its drop value was difficult to estimate.

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

The addition of this hill to Sub-Trichant status is due to LIDAR analysis, resulting in a 338.0m summit height and a 310.0m bwlch height, with these values giving this hill 28.0m of drop which is sufficient for it to be classified as a Sub-Trichant.

 
The full details for the hill are:

Group:  Cymoedd Gwent

Name:  Llanbradach Tip

OS 1:50,000 map:  171

Summit Height:  338.0m (LIDAR)

Summit Grid Reference:  ST 13939 91311 (LIDAR)

Bwlch Height:  310.0m (LIDAR)

Bwlch Grid Reference:  ST 13887 91328 (LIDAR) 

Drop:  28.0m (LIDAR)


Myrddyn Phillips (July 2019)






Sunday 28 July 2019

UKHillwalking Article - Twyn Llech and the Welsh – English border


UKHillwalking Article

UKHillwalking recently published an article on the research and survey of Twyn Llech and its summit position in relation to that of the border between Wales and England.  The original article and a link to it on the UKHillwalking website appear below.


Will England Reclaim its Share of a Welsh Mountain?
It's the high point near where the Welsh-English border runs over the Black Mountains, but there all certainty ended. Should it properly be called Black Mountain or Twyn Llech? And which country could rightfully lay claim to the summit? Following research by two independent surveyors, Myrddyn Phillips assisted by Mark Trengove, the mystery surrounding one of the most visited hills in South Wales has finally been cleared up... with a surprising conclusion.


Mark and I are both keen hill walkers with a common interest in hill bagging and the classification of hills. This particular hill was of interest, as its summit position and the location of the border between England and Wales, in relation to the summit, has been under debate. Was the summit on the Welsh side of the border and therefore could the hill be claimed as being Welsh, or was it in fact English? Our aim was to determine where the summit of the hill is positioned, measure its height and plot the course of the border between Wales and England as it crosses the summit plateau.


Twyn Llech

The Name

Rising above the Vale of Ewyas on its Welsh side, and the upper Olchon Valley on its English side, the hill is known by many as  Black Mountain; however research suggests that it was supplanted by early hill-list compilers from the old ridge name given to the main easterly spur of this hill range, and does not apply to the hill itself. This easterly ridge is now known as the 'Hatterrall Ridge' after its southerly outlier, Hatterrall Hill.

Enquiries with the local farming community unearthed the feature name of 'The thieves' stone'. This name was given by David Gains who farms in the Olchon Valley. David explained: 'It's hanging out on a slope, straight on top of the ridge, just on the Welsh side and about 3-4ft wide'. He first heard of this name from his father, who passed on a saying: 'If a sheep grazed the land around the stone and kept by the thieves' stone it would never get maggots'.

This name still appears on contemporary Ordnance Survey maps in its Welsh form of Llech y Lladron, and is given to a rock outcrop on the upper northerly section of the hill.

This and the name of Twyn Llech are the two main named features on this hill, and it is the latter that many know as this hill's referred to Welsh name, which can be translated as 'hill of the stone (or crag)'. This name still appears on Ordnance Survey maps positioned to the west of its summit. Therefore for the remainder of this article we'll refer to the hill as Twyn Llech.

Llech y Lladron


The Hill

Twyn Llech is positioned in the Black Mountains in the south-eastern part of Wales. This hill range has four main extended ridges oriented in a north-west to south-east direction, and Twyn Llech is the highest point of the most easterly of these main ridges.

The hill comprises grass and heather with a base of peat; it is not dramatic in nature but is a great bulk of a hill. The high point is situated toward the northerly section of the main easterly ridge, which extends for approximately 15km. It has two main recognised and individual summits on it, one of which is Twyn Llech and the second the southerly outlier Hatterrall Hill.

There are two significant marker lines on contemporary Ordnance Survey maps that follow the course of this easterly ridge. One is a public right of way that designates part of the Offa's Dyke long distance footpath, and the other is the land border between Wales and England. These are positioned next to one another on the maps. As the summit of the hill is positioned to the west of the ridge path, it has generally been accepted that it is therefore in Wales.

Part of the main eastern ridge


Research

Prior to visiting the hill I conducted extensive research into the position of the border between Wales and England. My hope was to find a written document that gives detail of the position of this land boundary, and especially for the course that it takes over the main easterly ridge of the Black Mountains.

A number of individuals, public bodies and organisations were contacted including the Powys Archives, Powys County Council, National Library of Wales, Longtown Historical Society, Ewyas Study Group, Hereford Record Office, Brecon History Society, Clwyd Powys Archaeological Trust, Hereford Border Authorities, Electoral Services, Boundary Commission, Ordnance Survey, HMSO, Electoral Commission, local historians and the Senedd. None of them could either supply or give information on any form of written document relating to where the land border between Wales and England is positioned. In fact many said that such a document did not exist. The only organisation that gave any indication as to where this border is positioned was the Ordnance Survey, and they simply instructed me to consult their maps.


The Summit

The summit area of this hill comprises a broad ridge of grass and heather with a base of peat. It is relatively flat. However, Twyn Llech has a distinguishable rise on the northerly part of this land, and a dip that leads south to another slight rise approximately 350 metres away, with the northerly high point being relatively easy to distinguish and the southerly high point comprising land that slightly undulates.

These two rises roughly match map detail. The Ordnance Survey give a 703m spot height on their contemporary 1:50,000 Landranger and 1:25,000 Explorer maps, positioned in the southerly part of a 700m continuous contour ring at SO 25586 35010. Harvey maps give a 706m spot height on their 1:40,000 Offa's Dyke South map which is positioned in the northerly part of a 705m continuous contour ring.


First on-site visit

This concentrated on determining the height and position of the northerly high point and its counterpart to the south. This was conducted during an extended walk I completed, taking in a number of other hills. This also prioritised another hill to the south that was surveyed as having less that 15m of drop and which is currently still listed as a Nuttall. The conditions for each survey were excellent with good visibility and little breeze.

The results of these two surveys are:

Northerly high point: 703.639m (converted to OSGM15) at SO 25520 35383

Southerly high point: 702.721m (converted to OSGM15) at SO 25572 35032

A Trimble GeoXH 6000 GNSS receiver was used to determine the height of Twyn Llech and with a 0.9m difference in height there was confidence that the northerly point is where the summit of Twyn Llech is positioned. As the southerly land undulates a second survey to give correlation and confirmation was sought, and the opportunity to do so came nine months later.


The Border

The second on-site visit gave Mark and I the opportunity to plot the course of the land border on the ground as it passes over the summit plateau of Twyn Llech. To do this we used a Garmin GPS Map 64s hand-held device that has access to the Ordnance Survey 1:50,000 mapping. By following the course of the border we determined that it was consistently positioned to the east of the flagged ridge path, and the path itself is also positioned to the east of the summit of both the northerly and southerly points. Having determined where the border lay according to 1:50,000 map detail, we paced from its position to where the Trimble was set up on the northerly summit and its southerly counterpart, with the former being 50 metres and the latter being 45 metres in distance. Therefore, according to contemporary Ordnance Survey 1:50,000 mapping, the summit of Twyn Llech is in Wales.

However sometimes things aren't as simple as they appear...

The second on-site visit had two aims. Firstly we wanted to determine the position of the land border according to Ordnance Survey 1:50,000 mapping, and secondly to take further data sets with the Trimble GeoXH 6000 from the northerly and southerly positions. The conditions for each survey were again ideal with good visibility and not a breath of breeze. The Trimble was placed on a rucksack, which was used as an improvised tripod to give elevation above its immediate surrounds. Respective measurement offsets were taken between its internal antenna and the ground below.

The results of these three further surveys appear below:

Northerly high point: 703.656m (converted to OSGM15) at SO 25520 35383

Southerly high point: 702.787m (converted to OSGM15) at SO 25558 35018

Southerly high point: 702.699m (converted to OSGM15) at SO 25566 35054

These results show excellent correlation with the first set of survey data and confirm that the northerly point is where the summit of Twyn Llech is positioned.

OS Six-Inch map published in 1887 that gives the border as the 'Watershed'


The Ordnance Survey Base Map

Our on-site visit had confirmed where the summit of Twyn Llech is positioned and had given the hill an accurate height. We now compared our findings to the series of Ordnance Survey Six-Inch maps.

For many years the Ordnance Survey Six-Inch map was considered their base map. This was the map for information to be fed onto. The scale was superseded in the 1950s by the 1:10,000 series of maps and was available as sheets until the 1980s when these maps were digitised. The Six-Inch map is still one of the best for giving detail, either numeric or positional, and it was this map that I turned to.

I consulted the series of Six-Inch maps and looked at detail surveyed in 1887 and published in the same year. The land border between Wales and England appears on this map as a split black line, as it does on the publicly available scales of the 1:50,000 and 1:25,000 maps. However, the line of this border on the Six-inch base map has one extremely important word against it - 'Watershed'. The word 'Watershed' also appears beside this border on the Ordnance Survey Vector Map Local that is hosted on the Geograph website and entitled the Interactive Coverage Map. Therefore this word and its implication have remained in the system of Ordnance Survey mapping for over 130 years.


Ordnance Survey Consultation

As there was discrepancy between our on-site findings using the 1:50,000 mapping and the Six-Inch and Vector Map Local maps the Ordnance Survey were consulted and they kindly forwarded the following information:

"Ordnance Survey is not directed by the Ordnance Survey Act 1841 or any other Act to show National boundaries, although they are shown on certain scales of mapping (1:50k / Landranger, does depict National Boundaries between England-Wales, England-Scotland). In OS's most detailed mapping product OS MasterMap the Welsh / English border is located accurately and correctly it is displayed as a County/UA Boundary.

"OS's 1:25k and 1:50k leisure maps are purely contextual to provide a navigational guide to the landscape. Given their scale, these maps should never be used for measuring and surveying purposes. Our leisure maps are derived from the accurate large-scale data but are generalised for clarity, therefore not every feature is shown in the same position as the source data, and we are satisfied with how they currently depict the location of the Welsh English border."

MasterMap is the Ordnance Survey digitised mapping which receives upwards of 10,000 individual updates per day, and as its name implies, this is the master map for Ordnance Survey data.

I was advised by Ordnance Survey that the placement of the border on MasterMap is 12 metres to the east of the grid coordinates I supplied them for the summit of Twyn Llech, meaning that MasterMap places the summit of this hill in Wales.


Boundary Commission for Wales Consultation

After consultation with Ordnance Survey I was advised to contact the Boundary Commission for Wales. If a change in border placement is required it is this organisation that would initiate it. They told me:

"There is no legal mechanism for reviewing the boundary between England and Wales. The boundary is fixed and would require primary legislation to develop a mechanism to make a change to it. The England-Scotland boundary does have such a mechanism and the review is performed jointly by the English and Scottish Boundary Commissions.

"As far as the Commission is concerned the boundary provided by Ordnance Survey, particularly that in its MasterMap product, is the definitive boundary.

"With regard to the specific area to which you referred, I confirm that it is the convention of this Commission that if we were to draw a boundary that it would follow either the top of a ridge-line to its peak or the bottom of a valley depending on the circumstance; where we are not following another easily identifiable boundary (road, railway line, centre of a river, etc.). It may be that when the boundary was originally drawn at the larger scale that that was the intention. We have no records which would ascertain that intention."


Conclusion

My conclusion from the research and survey I've conducted is that the border should be moved and placed on MasterMap going through the summit of Twyn Llech and that primary legislation should be initiated to instigate the mechanism required for such a change. This is based on the convention the Boundary Commission for Wales would adopt and the evidence that the border followed the watershed on this hill's summit plateau on selective Ordnance Survey maps for over 130 years. It is also based on the simple fact that it is the natural course of any boundary on an open mountain such as Twyn Llech to follow the ridge crest which is also the watershed. The simple fact of the matter is that no one had ever surveyed this hill for where its summit is positioned prior to our visit, therefore the border placement on MasterMap although very close to the summit is still 12 metres from it and in all probability was placed to the best of the respective cartographer's presumption of where the watershed is positioned.

So which nation rightly lays claim to the summit of Twyn Llech? I'd say both. If the reinstated course of the border is accepted then it can be considered a dual national hill.


Myrddyn Phillips with Mark Trengove