Monday 18 March 2024

Mapping Mountains – Summit Relocations – 200m Twmpau

 

200m Twmpau – Summit Relocations

The 200m Twmpau (thirty welsh metre prominences and upward) are the Welsh hills at or above 200m and below 300m in height that have a minimum drop of 30m.  Accompanying the main P30 list is a sub list entitled the 200m Sub-Twmpau with the qualification to 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.

The list is authored by Myrddyn Phillips and the posts that have appeared on Mapping Mountains detailing the summit relocations to the main P30 list and the sub list appear below presented chronologically in receding order.









Mapping Mountains - Summit Relocations - 200m Twmpau

Mynydd Bach Brechfa (SN 520 286) - 37th summit relocation

Significant Height Revisions post for Mynydd Bach Brechfa

Significant Name Changes post for Mynydd Bach Brechfa

 

There has been a Summit Relocation to a hill that is listed in the 200m 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 programme, with subsequent LIDAR analysis conducted by the DoBIH team and independently by Myrddyn Phillips. 

LIDAR image of Mynydd Bach Brechfa (SN 520 286)

The criteria for the list that this summit relocation applies to are:

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. 

200m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Mynydd Bach Brechfa and this was derived from the Ordnance Survey series of Six-Inch maps, 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 B4310 road to its north and west, and a minor road to its immediate south-east, and has the village of Brechfa towards the north north-east. 

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

When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the main P30 category and listed with a 294m summit height, based on the spot height that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map at SN 52029 28578. 

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

Since the original publication of the Welsh P30 lists on Geoff Crowder’s v-g.me website 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 5m contouring, with the uppermost contour being 295m, resulting in an estimated c 297m summit height based on interpolation and a summit relocation to SN 51818 28761.

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 Mynydd Bach Brechfa (SN 520 286)

LIDAR analysis gives the highest natural ground on this hill as 296.1m positioned at SN 52039 28618, and this position in relation to the previously listed summit position comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour, to a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit of a hill 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 296.1m and this is positioned at SN 52039 28618, 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 220 metres south-eastward from the previously listed summit position. 

 

The full details for the hill are: 

Group:  Mynydd Pencarreg 

Name:  Mynydd Bach Brechfa 

OS 1:50,000 map:  146

Summit Height:  296.1m (LIDAR) 

Summit Grid Reference (New Position):  SN 52039 28618 (LIDAR) 

Bwlch Height:  223.7m (LIDAR) 

Bwlch Grid Reference:  SN 51351 28147 (LIDAR) 

Drop:  72.3m (LIDAR) 

 

Myrddyn Phillips (March 2024)




Mapping Mountains - Summit Relocations - 200m Twmpau

Cae Cwar y Coed (SN 828 343) - 36th summit relocation

Significant Name Changes post for Cae Cwar y Coed

 

There has been a Summit Relocation to a hill that is listed in the 200m 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 Cae Cwar y Coed (SN 828 343)

The criteria for the list that this summit relocation applies to are:

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. 

200m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Cae Cwar y Coed and this was derived from the Tithe map, and it is adjoined to the Mynydd Epynt group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north-west and east, and the A40 road to its south, and has the town of Llanymddyfri (Llandovery) towards the west.

When the original 200m 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 248m summit height, based on the spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map at SN 82773 34291.  This position was subsequently changed to SN 82761 34285, based on on-site visits and GPS data recorded on the Hill Bagging website. 

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 Cae Cwar y Coed (SN 828 343)

LIDAR analysis gives the highest ground on this hill as 246.6m positioned at SN 82809 34336, and this position in relation to the previously listed summit position comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour, to a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit of a hill 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 246.6m and this is positioned at SN 82809 34336, 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 50 metres north-eastward from the previously listed summit position and importantly it is also positioned in a different field. 

 

The full details for the hill are: 

Group:  Mynydd Epynt 

Name:  Cae Cwar y Coed 

OS 1:50,000 map:  160

Summit Height:  246.6m (LIDAR) 

Summit Grid Reference (New Position):  SN 82809 34336 (LIDAR) 

Bwlch Height:  215.4m (LIDAR) 

Bwlch Grid Reference:  SN 83737 35272 (LIDAR) 

Drop:  31.2m (LIDAR) 

 

Myrddyn Phillips (March 2024)

  


Sunday 17 March 2024

Mapping Mountains – Summit Relocations – 200m Twmpau

 

Mynydd Bach Brechfa (SN 520 286) 

There has been a Summit Relocation to a hill that is listed in the 200m 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 programme, with subsequent LIDAR analysis conducted by the DoBIH team and independently by Myrddyn Phillips. 

LIDAR image of Mynydd Bach Brechfa (SN 520 286)

The criteria for the list that this summit relocation applies to are:

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. 

200m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Mynydd Bach Brechfa and this was derived from the Ordnance Survey series of Six-Inch maps, 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 B4310 road to its north and west, and a minor road to its immediate south-east, and has the village of Brechfa towards the north north-east. 

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

When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the main P30 category and listed with a 294m summit height, based on the spot height that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map at SN 52029 28578. 

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

Since the original publication of the Welsh P30 lists on Geoff Crowder’s v-g.me website 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 5m contouring, with the uppermost contour being 295m, resulting in an estimated c 297m summit height based on interpolation and a summit relocation to SN 51818 28761.

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 Mynydd Bach Brechfa (SN 520 286)

LIDAR analysis gives the highest natural ground on this hill as 296.1m positioned at SN 52039 28618, and this position in relation to the previously listed summit position comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour, to a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit of a hill 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 296.1m and this is positioned at SN 52039 28618, 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 220 metres south-eastward from the previously listed summit position. 

 

The full details for the hill are: 

Group:  Mynydd Pencarreg 

Name:  Mynydd Bach Brechfa 

OS 1:50,000 map:  146

Summit Height:  296.1m (LIDAR) 

Summit Grid Reference (New Position):  SN 52039 28618 (LIDAR) 

Bwlch Height:  223.7m (LIDAR) 

Bwlch Grid Reference:  SN 51351 28147 (LIDAR) 

Drop:  72.3m (LIDAR) 

 

Myrddyn Phillips (March 2024)

 

 

 

 

 

Saturday 16 March 2024

Mapping Mountains – Significant Height Revisions – The Fours – The 400m Hills of England

 

Rippon Tor (SX 746 755) 

There has been a Significant Height Revision that is retrospective 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 from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Rippon Tor (SX 746 755)

The criteria for the list this height revision affects are:

The FoursThe 400m Hills of England.  English hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are three categories of sub hills, the 400m Sub-Four category, the 390m Sub-Four category and the 390m Double Sub-Four category.  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 name the hill is listed by is Rippon Tor, and it is adjoined to the Broad Barrow group of hills, which are situated in Dartmoor in the south-west of the country, and it is positioned with the B3387 road to its north and minor roads to its west and south-east, and has the town of Bovey Tracey towards the east north-east. 

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

When the listing that is now known as The Fours – The 400m Hills of England was originally compiled by Myrddyn Phillips, this hill was listed with a 473m summit height, based on the spot height that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

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

When the 1st edition of the The Fours now co-authored by Myrddyn Phillips and Aled Williams was published by Europeaklist in December 2013 the summit height was amended to 477m, with an accompanying note stating:

Summit height from 1,563.8ft (476.65m [476.47m height relative to Ordnance Datum Newlyn]) levelled height on Ordnance Survey 1:2,500 map which matches the rounded up 1,564ft height on the Ordnance Survey New Popular One-Inch map.  The imperial height of 1,563ft (476.4m [476.2m height relative to Ordnance Datum Newlyn]) is also recorded on the Ordnance Survey Seventh Series One-Inch map.  Summit height of 473m on current Ordnance Survey 1:50,000 and 1:25,000 map.  Triangulation pillar with 475.905m flush bracket height on summit area.  The trig pillar is positioned within a wind shelter and is built on a concrete base with the ground at the base of the trig being approximately 475.555m - 475.605m in height, and as the high point of this hill is a substantial slab of rock positioned a few metres from the wind shelter and an approximate 1m higher than the base of the trig, the listed height of 477m can also be calculated from 475.6m (base of trig) + 1m = 476.6m.  However, there's still an unusual 3.6m discrepancy in the current 473m Ordnance Survey map height.

When the 2nd edition of The Fours – The 400m Hills of England co-authored by Myrddyn Phillips and Aled Williams was published by Mapping Mountains Publications in April 2018, the height of this hill was reassessed and it was listed as 476m, with an accompanying note stating:

476m summit height taken from the 1,563.8ft (476.65m) surface height on the OS Six-Inch map published in 1886.  Triangulation pillar with 475.905m flush bracket height situated on the summit area and positioned in a wind shelter with its flush bracket 60cm lower than the summit of the hill, this corresponds with the 476.47m surface height relative to Ordnance Datum Newlyn.  However, there is still an unusual 3.5m discrepancy between the 476.47m height and the current 473m OS map height.

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 Rippon Tor (SX 746 755)

LIDAR analysis gives the highest ground on this hill as 476.3m positioned at SX 74661 75574, 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 476.3m and this was derived from LIDAR analysis, this is 3.3m higher than its originally listed 473m summit height, which appears as a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

 

The full details for the hill are:

Group:  Broad Barrow

Name:  Rippon Tor

OS 1:50,000 map:  191

Summit Height (New Height):  476.3m (LIDAR)

Summit Grid Reference:  SX 74661 75574 (LIDAR)

Col Height:  357.6m (LIDAR)

Col Grid Reference:  SX 73917 79116 (LIDAR)

Drop:  118.7m (LIDAR)

 

Myrddyn Phillips and Aled Williams (March 2024)