Banc Tŷ Hen (SN 650 895)
There has been a Summit Relocation to a hill that is listed in the 100m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips.
LIDAR image of Banc Tŷ Hen (SN 650 895) |
100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m
minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with
the criteria for this sub category being all Welsh hills at or above 100m and
below 200m 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.
The 100m Twmpau by Myrddyn Phillips |
Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips |
When the original Welsh 100m P30 list was published on Geoff Crowder’s v-g.me website this hill was listed with a 157m summit height based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map and which is positioned at SN 64770 89387.
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.
The summit height produced by LIDAR analysis is 157.4m and is positioned at SN 65012 89554. When compared to the original listed summit position the above detail comes within the parameters of the Summit Relocations used within this page heading, these parameters are:
The term Summit Relocations applies when the hill’s high point is found to be positioned; in a different field, to a different feature such as in a conifer plantation, placed within a different map contour, to a different point where a number of potential summit positions are within close proximity, or 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 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 LIDAR analysis is 157.4m and this is positioned at SN 65012 89554, this is approximately 300 metres north-eastward from where the original listed summit was given which was to the position of the 157m spot height on the Ordnance Survey 1:25,000 Explorer map.
The full details for the hill are:
Group: Pumlumon
Name: Banc Tŷ Hen
OS 1:50,000 map: 135
Summit Height: 157.4m
(LIDAR)
Summit Grid Reference (New Position): SN 65012 89554 (LIDAR)
Bwlch Height:
63.7m (LIDAR)
Bwlch Grid Reference:
SN 65510 89668 (LIDAR)
Drop: 93.6m (LIDAR)
Dominance: 59.49%
(LIDAR)
Myrddyn Phillips (April 2021)
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