Maes Llwyn (SH 435 920) – 30-99m Sub-Twmpau deletion
There has been a deletion to the list of 30-99m 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 Maes Llwyn (SH 435 920) |
30-99m Twmpau – Welsh hills at or above 30m and below 100m in height that have 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m 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 30-99m Twmpau by Myrddyn Phillips |
When the original 30-99m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.
After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with 25m of drop, based on the 77m summit spot height positioned on or near to a covered reservoir that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map and the 52m bwlch spot height that appears on the Ordnance Survey 1:50,000 Landranger map.
Extract from the Ordnance Survey 1:25,000 Explorer map |
Therefore, the deletion of this hill from 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 74.0m height to a natural summit and a 54.9m bwlch height, with these values giving this hill 19.1m of drop, which is insufficient for it to be classified as a 30-99m Sub-Twmpau.
The full details for the hill are:
Group: Ynys Môn
Name: Maes Llwyn
OS 1:50,000 map: 114
Summit Height: 74.0m (LIDAR)
Summit Grid Reference: SH 43593 92022 (LIDAR)
Bwlch Height: 54.9m (LIDAR)
Bwlch Grid Reference: SH 43658 91747 (LIDAR)
Drop: 19.1m (LIDAR)
Myrddyn Phillips (August
2021)
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