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