Mapping Mountains – Hill Reclassifications – 30-99m Twmpau

Cae Benglog (SH 316 380) – 30-99m Sub-Twmpau addition

There has been an addition to the 30-99m Twmpau due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

30-99m Twmpau - Welsh hills at and 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 and above 30m and below 100m in height with 20m and more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

This hill did not appear in the accompanying Hills to be surveyed sub list when the original Welsh P30 hills were published on Geoff Crowder’s v-g.me website as it did not meet the criteria for this sub category; however this sub list has now been standardised including the addition of interpolated drop values and heights.

Prior to LIDAR analysis this hill was listed with an estimated c 19m of drop based on the 86m spot height positioned at SH 31361 38368 on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 67m based on bwlch contouring at 5m intervals and between 65m – 70m on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website.

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

The name of the bounded land where the summit of this hill is situated is Cae Benglog with these details derived from the Tithe map and the hill is adjoined to the Pen Llŷn group of hills, which is situated in the north-west part of North Wales (Region A, Sub-Region A1), and is positioned overlooking the A 497 road which is to its north-east and has the small community of Morfa Nefyn t0 its north-west and the town of Pwllheli towards the south-east.

If wanting to visit the hill permission to do so should be sought as it is not a part of designated open access land, with the nearest public footpath close to the summit to its east.

The addition of Cae Benglog to 30-99m Sub-Twmpau status is due to LIDAR analysis conducted by Myrddyn Phillips.  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 hill the following details:

Cae Benglog

Summit Height:  86.8m

Summit Grid Reference:  SH 31635 38073

Bwlch Height:  65.9m

Bwlch Grid Reference:  SH 31523 38448

Drop:  20.9m

LIDAR image of Cae Benglog

Therefore, the 86.779m LIDAR analysis for the summit position at SH 31635 38073 and the 65.873m LIDAR analysis for the bwlch position at SH 31523 38448 gives this hill 20.906m of drop, which is sufficient for 30-99m Sub-Twmpau status.

A point to the north-west of this summit and which is given an 86m spot height on the Ordnance Survey 1:25,000 Explorer map was also examined via LIDAR, resulting in a 85.355m height positioned at SH 31355 38373.

The full details for the hill are:

Group:  Pen Llŷn

Name:  Cae Benglog

Summit Height:  86.8m (LIDAR)

Summit Grid Reference:  SH 31635 38073 (LIDAR)

OS 1:50,000 map:  123

Drop:  20.9m (LIDAR)

Myrddyn Phillips (April 2018)