Mapping Mountains – Hill Reclassifications – 30-99m Twmpau

Cae Doctor (SH 304 399) – 30–99m Sub-Twmpau reclassified to 30-99m Twmpau

There has been confirmation of a Hill Reclassification to the list of 30-99m Twmpau, with the summit height, its location, the drop and status of the hill confirmed by LIDAR analysis, with the bwlch LIDAR analysis initially conducted by Aled Williams, and a subsequent summit survey with the Trimble GeoXH 6000 conducted by Myrddyn Phillips, with the latter taking place on the 3^rd October 2018.

The summit of Cae Doctor (SH 304 399)

The criteria for the list that this reclassification applies to are:

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 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.

When the original Welsh 30-99m height band of P30 hills were published on Geoff Crowder’s v-g.me website this hill appeared in the accompanying Hills to be surveyed sub list as it did not meet the criteria then used for the main P30 list; however this sub list has now been standardised with drop values and interpolated heights also included in the main P30 and the accompanying sub list.

When this list was standardised with interpolated heights and drop values included this hill was listed with an estimated c 30m of drop based on the 68m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 38m based on interpolation of 10m bwlch contouring.

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

The details for this hill were reassessed when the Ordnance Survey Interactive Coverage Map hosted on the Geograph website became available online, and this map has a 37m spot height positioned at SH 30870 40378 on a minor road on the area of this hill’s bwlch, and if taken as a part of this hill’s drop this would give a value of 31m.

The locally known name for the bounded land where the summit of this hill is situated is Cae Doctor, and this is the name the hill is now listed by.  The hill is adjoined to the Pen Llŷn group of hills, which are situated in the western part of North Wales (Region A, Sub-Region A1), and it has the A497 road to its immediate south-east and the B4417 road to its north-west, and has the small town of Nefyn to the north.

The confirmation of the reclassification of Cae Doctor to 30-99m Twmpau status is due to LIDAR analysis of the bwlch conducted by Aled Williams and a summit survey with the Trimble GeoXH 6000 conducted by Myrddyn Phillips, resulting in a 67.0m summit height and a 35.8m bwlch height, with these values giving this hill 31.2m of drop which is sufficient for it to be classified as a 30-99m Twmpau.

The Trimble GeoXH 6000 gathering data at the summit of Cae Doctor (SH 304 399)

The full details for the hill are:

Group:  Pen Llŷn

Name:  Cae Doctor

OS 1:50,000 map:  123

Summit Height:  67.0m (converted to OSGM15)

Summit Grid Reference:  SH 30425 39978

Bwlch Height:  35.8m (LIDAR)

Bwlch Grid Reference:  SH 30747 40107 (LIDAR)

 

Drop:  31.2m (Trimble summit and LIDAR bwlch)

My thanks to Aled Williams for initial LIDAR analysis of this hill’s bwlch

For details of the summit survey of this hill

Myrddyn Phillips (February 2019)