Myrddyn Phillips - Mapping Mountains: Mapping Mountains - Summit Relocations - Y Pedwarau

Y Pedwarau - The 400m Hills of Wales – Summit Relocations

Y Pedwarau are the Welsh hills at or above 400m and below 500m in height that have a minimum drop of 30m. Accompanying the main P30 list are five sub lists; these are the 500m Sub-Pedwar, 500m Double Sub-Pedwar, 400m Sub-Pedwar, 390m Sub-Pedwar and 390m Double Sub-Pedwar category’s, with their criteria detailed in the respective Change Registers that have been created and which are linked in their above titles, with the Introduction to this list being published on Mapping Mountains on the 30^th January 2017.

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

Mapping Mountains - Summit Relocations - Y Pedwarau - The 400m Hills of Wales

Lan Ucha Ty’n y Wern (SN 996 423) - 38th summit relocation

Significant Name Changes post for Lan Ucha Ty'n y Wern

There has been a Summit Relocation to a hill that is listed in the Y Trichant – The 300m Hills of Wales and the Y Pedwarau – The 400m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips.

LIDAR image of Lan Ucha Ty'n y Wern (SN 996 423)

The criteria for the lists this summit relocation affects 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

Y Pedwarau – The 400m Hills of Wales – Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are five categories of sub hills, with this hill listed in the 390m Sub-Pedwar category. The criteria for this category are all Welsh hills at or above 390m and below 400m in height that have 30m minimum drop. The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is now listed by is Lan Ucha Ty’n y Wern 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 the B4519 road to its north-east and a minor road to its south, and has the small community of Capel Uchaf (Upper Chapel) towards the 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 included in the main P30 list with a 398m summit height, based on the spot height positioned at SN 996 423 that appears on the contemporary Ordnance Survey 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 the highest ground on this hill as 396.9m positioned at SN 99625 42340. However, this is a part of a raised field boundary and 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 Lan Ucha Ty'n y Wern (SN 996 423)

The height produced by LIDAR analysis to the natural summit of this hill is 396.7m positioned at SN 99632 42324, and this position in relation to raised field boundary 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 396.7m and this is positioned at SN 99632 42324, this position is close to where the 398m spot height appears on the Ordnance Survey 1:25,000 Explorer map, and is approximately 16 metres south-eastward from where the high point of the raised field boundary is positioned.

The full details for the hill are:

Group: Mynydd Epynt

Name: Lan Ucha Ty’n y Wern

OS 1:50,000 map: 147, 160

Summit Height: 396.7m (LIDAR)

Summit Grid Reference (New Position): SN 99632 42324 (LIDAR)

Bwlch Height: 362.65m (LIDAR)

Bwlch Grid Reference: SN 99601 42833 (LIDAR)

Drop: 34.1m (LIDAR)

Myrddyn Phillips and Aled Williams (July 2024)

Mapping Mountains - Summit Relocations - Y Pedwarau - The 400m Hills of Wales

Mynydd Bwlch y Groes (SN 868 356) - 37th summit relocation

There has been a Summit Relocation to a hill that is listed in the Y Pedwarau – The 400m 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.

Mynydd Bwlch y Groes (SN 868 356)

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

Y Pedwarau – The 400m Hills of Wales. Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, the list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Mynydd Bwlch y Groes 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 the A40 road to its south-west and a minor road to its immediate east, and has the village of Pontsenni (Sennybridge) towards the south-east.

Summit extract from the Ordnance Survey 1:25,000 Explorer map

When the 1^st edition of the Y Pedwarau was published by Europeaklist in May 2013, this hill was listed with 140m of drop, based on the 442m summit spot height adjoined to a triangulation pillar positioned at SN 86857 35624 that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and a 302m bwlch spot height that appears on the Ordnance Survey 1:25,000 Explorer map.

Bwlch extract from the Ordnance Survey 1:25,000 Explorer map

The details for this hill were reassessed based on a Trimble GeoXH 6000 summit survey, resulting in a 441.7m height positioned at SN 86857 35625 and contour detail on the OS Maps website. This mapping was the replacement for OS Get-a-map and until recent times had contours at 5m intervals which were proving consistently more accurate compared to the 5m contours that sometimes appear on the Ordnance Survey 1:25,000 Explorer map and used to appear on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. This mapping had bwlch contouring between 305m – 310m, with interpolation placing the height of the bwlch as an estimated c 306m, resulting in the drop value of this hill being amended to an estimated c 136m.

The Trimble GeoXH 6000 gathering data beside the triangulation pillar on Mynydd Bwlch y Groes

LIDAR summit image of Mynydd Bwlch y Groes (SN 868 356)

LIDAR close up summit image of Mynydd Bwlch y Groes (SN 868 356)

LIDAR analysis gives the highest ground on this hill as 441.9m positioned at SN 86898 35691, and matching that produced by the Trimble GeoXH 6000 survey with 441.7m positioned at SN 68656 35625 for ground beside the trig pillar, and this 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 judged to be 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 height produced by LIDAR analysis to the summit of this hill is 441.9m and is positioned at SN 86898 35691, 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 66 metres north north-eastward from where the previously listed summit is positioned and importantly the summit feature has altered from beside the triangulation pillar to featureless ground.

The full details for the hill are:

Group: Mynydd Epynt

Name: Mynydd Bwlch y Groes

OS 1:50,000 map: 160

Summit Height: 441.9m (LIDAR)

Summit Grid Reference (New Position): SN 86898 35691 (LIDAR)

Bwlch Height: 305.05m (LIDAR)

Bwlch Grid Reference: SN 88817 38632 (LIDAR)

Drop: 136.9m (LIDAR)

Myrddyn Phillips and Aled Williams (June 2024)

Mapping Mountains - Summit Relocations - Y Pedwarau - The 400m Hills of Wales

Panylau Gwynion (SH 935 063) - 36th summit relocation

Survey post for Panylau Gwynion

Panylau Gwynion (SH 935 063)

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

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Panylau Gwynion 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 the A470 road to its south-west and a minor road to its south-east, and has the village of Talerddig towards the south.

When the 1^st edition of the Y Pedwarau was published by Europeaklist in May 2013, this hill was listed with 39m of drop, based on the 451m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map at SH 93575 06311 and a 412m bwlch spot height that appeared on the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map.

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

The upper part of this hill has two 450m map ring contours. The 451m map spot height appears in a relatively large 450m contour that until recent times was a part of a conifer plantation, whilst just to the west of the plantation’s boundary fence was a small 450m map ring contour on open ground that logs on the Hill Bagging website reported as a knoll and which could be higher.

The Trimble GeoXH 6000 gathering data from the lower deforested top with the higher summit of Panylau Gwynion in the background

The Trimble GeoXH 6000 gathering data at the heathery knoll summit of Panylau Gwynion with the lower deforested top in the background

However, it was not until the Trimble GeoXH 6000 survey that the details for this hill could be accurately re-assessed. The summit height and position produced by the Trimble GeoXH 6000 survey is 450.3m positioned at SH 93557 06357, as opposed to 449.1m positioned at SH 93575 06303 to the high point of what used to be within the conifer plantation, and this position in relation to that previously given 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 judged to be 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 the Trimble GeoXH 6000 survey is 450.3m and this is positioned at SH 93557 06357, 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 55 metres south south-eastward from where the previously listed summit is positioned.

The full details for the hill are:

Group: Carnedd Wen

Name: Panylau Gwynion

OS 1:50,000 map: 125

Summit Height: 450.3m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference (New Position): SH 93557 06357 (Trimble GeoXH 6000)

Bwlch Height: 412m (spot height)

Bwlch Grid Reference: SH 93627 06715 (spot height)

Drop: 38m (Trimble GeoXH 6000 summit and spot height bwlch)

Myrddyn Phillips and Aled Williams (September 2022)

Tuesday, 20 September 2022

Mapping Mountains - Summit Relocations - Y Pedwarau - The 400m Hills of Wales

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