Mapping Mountains – Hill Reclassifications – 30-99m Twmpau

Dinas Dinlle (SH 436 564) – 30-99m Twmpau addition

There has been an addition to the Twmpau (thirty welsh metre prominences and upward) list with this hill being included in the 30-99m height band.  Accompanying all the 100m height band of hills within the Twmpau are sub lists with the one attached to this list being entitled the 30-99m Sub-Twmpau.

The details relating to this hill’s addition are retrospective as its P30 status is due to detail on the Ordnance Survey enlarged mapping hosted on the Geograph website and which was first spotted by Chris Watson, its status has subsequently been confirmed from a survey with the Trimble GeoXH 6000 which was conducted on the 26^th December 2013.

The criteria for 30-99m Twmpau status is all Welsh hills at or above 30m and below 100m in height with 30m minimum drop, whilst the criteria for 30-99m Sub-Twmpau status is all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop.

Prior to Chris Watson raising the probability of this hill being a P30 and its subsequent survey it had remained unclassified, as the Ordnance Survey 1:50,000 Landranger map gives a 31m summit spot height and bwlch contouring between 0m – 10m, whilst the 1:25,000 Explorer map gives an uppermost 30m ring contour and the same bwlch contouring, this implied that the hill did not have the required 30m of drop to qualify for Twmpau status.

The hill is positioned in the Moel Hebog range and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Mynydd Mawr (SH 539 546) and is situated on the outskirts of the small community that takes its name from the hill; Dinas Dinlle, and is positioned with the sea to its immediate west which has eroded some of its western slopes over recent years.  If wanting to visit the hill it can be easily accessed from the car park adjacent to the sea front from where a path heads up its northern slopes.

The name of the hill is Dinas Dinlle and as its name implies the upper section of the hill comprises an ancient hill fort, it was included as a 30-99m Twmpau as the Ordnance Survey enlarged mapping hosted on the Geograph website has contours at 5m intervals giving the hill an uppermost contour of 35m and bwlch contouring between 0m – 5m, these values give the hill an estimated drop of c 31m – c 32m.  The summit of this hill has subsequently been surveyed with the Trimble GeoXH 6000 as 34.7m (converted to OSGM15) and with a 4.1m bwlch height ascertained from LIDAR analyis, these values give this hill 30.6m of drop. 

The full details for the hill are:

Cardinal Hill:  Mynydd Mawr

Summit Height:  34.7m (converted to OSGM15)

Name:  Dinas Dinlle

OS 1:50,000 map:  115, 123

Summit Grid Reference:  SH 43676 56438

Drop:  30.6m

Dinas Dinlle (SH 436 564) confirmed as a 30-99m Twmpau

For details on the survey that confirmed this hill’s 30-99m Twmpau status

Myrddyn Phillips (July 2017)

Mapping Mountains – Hill Reclassifications – Y Trechol – The Dominant Hills of Wales

Dinas Dinlle (SH 436 564) - Dominant addition

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales due to detail included on the Ordnance Survey enlarged mapping hosted on the Geograph website and which was first spotted by Chris Watson, and subsequently confirmed via a survey with the Trimble GeoXH 6000.  This has resulted in the hill being added to the Dominant list.  With the criteria for inclusion to this list being those Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

The details relating to this hill’s inclusion as a Dominant hill are retrospective as it was added to the list shortly after its initial compilation and later appeared in the Moel Hebog group of hills when published on Mapping Mountains on the 28^th January 2016.

Prior to Chris Watson raising the probability of this hill being a P30 and its subsequent inclusion as a Dominant hill it had remained unclassified, as the Ordnance Survey 1:50,000 Landranger map gave a 31m summit spot height and bwlch contouring between 0m – 10m, whilst the 1:25,000 Explorer map gave an uppermost 30m ring contour and the same bwlch contouring, which implied that the hill did not have the required 30m of drop to be considered for Dominant status.

The hill is positioned in the Moel Hebog group of hills and is placed in the Region of North Wales (Region A, Sub-Region A1) and is situated on the outskirts of the small community that takes its name from the hill; Dinas Dinlle, and is positioned with the sea to its immediate west which has eroded much of its slopes over recent years.  If wanting to visit the hill it can be easily accessed from the car park adjacent to the sea front from where a path heads up its northern slopes.

The name of the hill is Dinas Dinlle and as its name implies the upper section of the hill comprises an ancient hill fort, it was included as a 30-99m Twmpau as the Ordnance Survey enlarged mapping hosted on the Geograph website has contours at 5m intervals giving the hill an uppermost contour of 35m and bwlch contouring between 0m – 5m, these values give the hill an estimated drop of c 31m – c 32m.  The summit of this hill has subsequently been surveyed with the Trimble GeoXH 6000 as 34.7m (converted to OSGM15) and with a 4.1m bwlch height ascertained from LIDAR analyis, these values give this hill 30.6m of drop and 88.22% dominance. 

The full details for the hill are:

Group:  Moel Hebog

Name:  Dinas Dinlle

Dominance:  88.22%

OS 1:50,000 map:  115, 123

Summit Grid Reference:  SH 43676 56438

Summit Height:  34.7m (converted to OSGM15)

Drop Summit to Bwlch:  30.6m

Drop Bwlch to ODN:  4.1m

Dinas Dinlle (SH 436 564) now classified as a Dominant hill

For details on the survey that confirmed this hill’s Dominant status

Myrddyn Phillips (February 2017)

Mapping Mountains – Trimble Surveys – Moel Hebog

26.12.13  Dinas Dinlle (SH 436 564)

Dinas Dinlle (SH 436 564)

Before the customary Boxing Day Bubble and Squeak we headed down for a wander on the beach at Dinas Dinlle and watched the sea sky subtly change its grey hue as the westerly’s blew in an occasional shower.

This part of the north-west coast of Wales takes its name from the old Iron Age hill fort that overlooks the pebble beach.  Only part of this ancient structure still remains as the sea has eroded much of its western side that only a double semi-circular rampart remains.

This hill was first proposed as a P30 by Chris Watson who spotted that the Ordnance Survey enlarged mapping on the Geograph website has a small uppermost c 35m ring contour at the summit, and as the bwlch contouring is between 0 – c 5m it means this hill should have a minimum of 30m of drop.

I’d only visited once before and hold fond memories of the excursion.  Today I was accompanied by my brother; Bryn and a good friend; Alun.  The ascent from the car park next to the beach is on a good path, past an interpretive board giving the history of the site and up to the summit, which is now undergoing work to try and stabilise it.

The last few metres to the summit of Dinas Dinlle.

On my previous visit we’d looked out on a dramatic sky as the lowering sun shot beams of light from behind large sea clouds.  Today the breeze blew and families were walking the cliff edge and on the beach, with dogs running in to the water chasing tennis balls.

The highest point is easily identifiable and is part of the land that is now being stabilised.  Five minutes of data was gathered and Bryn had the honour of switching the equipment off before we ventured down to the beach for half an hours stroll.

The Trimble GeoXH 6000 on the high point of Dinas Dinlle with Bryn admiring the view.

I didn't attempt to locate the critical bwlch as more pressing matters of dinner were calling.  However, map contouring and the view from the summit suggests it is placed at SH 439 562.

Survey Result:

Dinas Dinlle

Summit Height:  34.7m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 43676 56438 (Trimble GeoXH 6000)

Bwlch Height:  4.1m (LIDAR)

Bwlch Grid Reference:  SH 43922 55774 (LIDAR)

Drop:  30.6m (Trimble GeoXH 6000 summit and LIDAR bwlch) (30-99m Twmpau addition)

Dominance:  88.22% (Trimble GeoXH 6000 summit and LIDAR bwlch) (Dominant addition)

For further details please consult the Trimble survey spreadsheet click {here}