Allt yr Hafod (SN 668 442)
There has been a Summit Relocation 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 detail on contemporary maps
produced from Ordnance Survey data and LIDAR analysis conducted by Myrddyn
Phillips.
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LIDAR image of Allt yr Hafod (SN 668 442) |
The criteria for the list that this summit
relocation applies to are:
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Y Trichant - The 300m Hills of Wales by Myrddyn Phillips |
The name the hill is listed by is Allt yr Hafod,
and it is adjoined to the Esgair Wen 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 south-east and the
A482 road to its south-west, and has the town of Llanbedr Pont Steffan
(Lampeter) towards the west north-west.
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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.
LIDAR analysis gives the highest ground on this
hill as 310.3m positioned at SN 66863 44189.
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.
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LIDAR summit image of Allt yr Hafod (SN 668 442) |
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LIDAR close up summit image of Allt yr Hafod (SN 668 442) |
The height produced by LIDAR analysis to the
natural summit of this hill is 310.2m positioned at SN 66859 44201, 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 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 310.2m and this is positioned at SN 66859 44201, this position is close
to where the 311m spot height appears on the contemporary Ordnance Survey 1:25,000
Explorer map, and is approximately 12 metres northward from where the high point
of the raised field boundary is positioned.
The full details for the hill are:
Group: Esgair Wen
Name: Allt yr Hafod
OS 1:50,000 map: 146
Summit Height: 310.2m (LIDAR)
Summit Grid Reference
(New Position): SN 66859 44201 (LIDAR)
Bwlch Height: c 288m (interpolation)
Bwlch Grid
Reference: SN 67104 44293 (interpolation)
Drop: c 22m (LIDAR summit and interpolated bwlch)
Myrddyn Phillips (April
2023)
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