Thursday, 23 May 2019

Mapping Mountains – Hill Reclassifications – 100m Twmpau


Barclodiau (SH 466 848) – 100m Sub-Twmpau reclassified to 100m Twmpau

There has been confirmation of a reclassification to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis and a subsequent summit survey with the Trimble GeoXH 6000, with both conducted by Myrddyn Phillips and the latter taking place on the 28th October 2018.

Barclodiau (SH 466 848)

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

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 name of the hill is Barclodiau, and it is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it has the A5025 road to its north-east and the B5111 road to its west, and is positioned between the small communities of Llannerch-y-medd towards its west and Moelfre towards its east north-east.  

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was included in the Hills to be surveyed sub list that accompanied the main P30 list, as it did not meet the criteria then used in this list. 

When 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 an estimated c 30m of drop, based on the 168m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 138m based on interpolation of 5m contouring.

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

The drop value for this hill was re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website became available online; this mapping is entitled the Interactive Coverage Map.  Although this mapping has the same 5m contour intervals as the 1:25,000 Explorer map its scale is greatly enlarged giving the opportunity for better interpolation.  This re-assessment resulted in the estimated c 30m drop value for this hill remaining the same.

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website

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 confirmation of the reclassification of Barclodiau to 100m Twmpau status is due to LIDAR analysis, with a subsequent summit survey with the Trimble GeoXH 6000 resulting in a 168.6m Trimble summit height and a 137.1m LIDAR bwlch height, with these values giving this hill 31.5m of drop which is sufficient for it to be classified as a 100m Twmpau.

The Trimble GeoXH 6000 gathering data at the summit of Barclodiau


The full details for the hill are:

Group:  Ynys Môn

Name:  Barclodiau

OS 1:50,000 map:  114, 115

Summit Height:  168.6m (converted to OSGM15)

Summit Grid Reference:  SH 46674 84803

Bwlch Height:  137.1m (LIDAR)

Bwlch Grid Reference:  SH 46583 85000 (LIDAR)

Drop:  31.5m (Trimble summit and LIDAR bwlch)







Wednesday, 22 May 2019

Mapping Mountains – Significant Name Changes – 100m Twmpau and Y Trechol – The Dominant Hills of Wales


Cefn Cribwr (SS 883 829)

There has been a Significant Name Change 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 and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Cefn Cribwr

The criteria for the two listings that this name change applies to are:

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.

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height, with the Introduction to the Mapping Mountains publication of this list appearing on the 3rd December 2015.

The hill is adjoined to the Cymoedd Morgannwg group of hills, which are situated in the central part of South Wales (Region C, Sub-Region C2), and it is encircled by roads with a minor road to its south and east, the M4 further to its south and the Tycribwr Hill B4281 to its west north-west, and has the town of Pen-y-bont ar Ogwr (Bridgend) towards its south-east.

This hill was first listed in the original Welsh 100m P30 list published on Geoff Crowder’s v-g.me website, under the name of Tycribwr Hill, which is a name that is positioned following a road to the west north-west of this hill’s summit on contemporary Ordnance Survey 1:25,000 Explorer maps of the day.


Tycribwr Hill    134m    SS883829    170  151


During my early hill listing I paid little regard to name placement on the map, or the meaning of names and to what feature the name was appropriately applied to.  Therefore I prioritised names for listing purposes that I now understand are either inappropriate or where another name is viewed as being more appropriate, and as the name of Tycribwr Hill seems to apply to a part of the B4281 road that heads south-west from Tycribwr farm and as such is not the name of the hill, I therefore wanted to substantiate that the name of Cefn Cribwr had been applied to this hill and not just the small community by the same name that is positioned on its ridge crest.

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

Since publication of these P30 lists on Geoff Crowder’s v-g.me website there have been a number of Ordnance Survey maps made available online, some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website, whilst others are current and digitally updated such as the Vector Map Local hosted on the Geograph website and which is named the Interactive Coverage Map.  One of the historic maps now available is the Ordnance Survey One-Inch ‘Old Series’ map which formed the basis for the change in this hill’s listed name.

The One-Inch ‘Old Series’ map was the first map that the Ordnance Survey produced, and their publication culminated from the whole of Britain being surveyed between 1791 and 1874 and the detail gathered therein produced at a scale of one inch to the mile and published in sheet format between 1805 and 1874.  The One-Inch ‘Old Series’ maps for the whole of Wales are now available online; they are also available in map format as enlarged and re-projected versions to match the scale and dimensions of the Ordnance Survey 1:50,000 Landranger series and are published by Cassini.  This series of maps form another important part in the study of Welsh upland place-names and bridge the timeframe leading up to the production of the Ordnance Survey base map of the Six-Inch series, and importantly for this hill and its listed name, it is this map that shows the extended Cefn Cribwr takes in land comprising the extended ridge that this hill is a part of and not just the small community situated on its ridge crest.

Extract from the Ordnance Survey One-Inch 'Old Series' map

Therefore, the name this hill is now listed by in the 100m Twmpau and Y Trechol – The Dominant Hills of Wales is Cefn Cribwr, and this was derived from the Ordnance Survey One-Inch ‘Old Series’ map.


The full details for the hill are:

Group:  Cymoedd Morgannwg

Name:  Cefn Cribwr

Previously Listed Name:  Tycribwr Hill 

OS 1:50,000 map:  170

Summit Height:  133.8m (LIDAR)

Summit Grid Reference:  SS 88331 82914 (LIDAR)

Bwlch Height:  75.7m (LIDAR)

Bwlch Grid Reference:  SS 86323 83463 (LIDAR)
 
Drop:  58.2m (LIDAR)

Dominance:  43.47% (LIDAR)


Myrddyn Phillips (May 2019)



Tuesday, 21 May 2019

Mapping Mountains – Trimble Surveys – Carneddau


17.02.19  Cribau (SH 732 641), Pt. 504.7m (SH 744 624) and Cefn Cyfarwydd (SH 752 630)

Cefn Cyfarwydd (SN 752 630)

Much of the north-eastern Carneddau are a world apart compared to their higher adjacent hills as their land is dominated by heather which always gives an added sense of wilderness.  These hills stretch from the higher peaks of Creigiau Gleision and Pen Llithrig y Wrach north-eastward toward the coastal plains of the Afon Conwy.

Along with Aled and Mark we planned to visit three of these hills with each being surveyed.  Two of which are marginal P15s and are listed in the Welsh Highlands list (Yr Uchafion) whilst the third; Cefn Cyfarwydd is a potential new Dewey with OS Maps indicating that the 477m bwlch spot height that appears on the Ordnance Survey 1:25,000 Explorer map is in fact on a separate contour ring implying that the critical bwlch is significantly lower.

We met in Trefriw and spent an hour in a café enjoying conversation and laughs over breakfast as the forecast rain materialised.  It was around 10.00am as we indulged in our morning meal, and the rain was forecast to continue until at least midday.  After breakfast Mark drove on the narrow road toward Llyn Cowlyd were he parked and we sat in his car watching the rain and wind sweep in and batter the land around us.

Met office weather forecasts can be incredibly accurate and we had our boots on, or in my case my wellies, and walking in dull but dry conditions by 12.20pm, following the track heading up toward an old quarry above the northern part of Llyn Cowlyd.

The first hill on the surveying agenda was Cribau, which we’d all previously visited, a long time ago for me when I surveyed it with my basic levelling staff.  It has an attractive summit consisting of two tops, each was surveyed and although the rain had stopped the strong wind was still present and I hoped that the Trimble would remain in place during the five minutes data collection on each top.

Gathering data at the first position surveyed for the summit of Cribau

Between the two tops of Cribau

Gathering data at the second position surveyed for the summit of Cribau

I’ve always enjoyed this north-eastern land of the Carneddau with its rock carved summits and thick heather, few people seem to visit these hills compared to their easier underfoot higher neighbours and they have a feel of remoteness and solitude enhanced by the elongated lake of Llyn Cowlyd, which today glistened with brief bursts of sunlight giving a silvery sheen to the grey cloud and rising hillsides above.

Gathering data at the critical bwlch of Cribau

Llyn Cowlyd

Our downward route consisted of the customary bit of heather bashing before the inward track was re-joined; this brought us down to the dam of Llyn Cowlyd from where a convenient path continued through the heather gaining height toward our next point to survey; the bwlch of a c 500m hill positioned between Creigiau Gleision and Cefn Cyfarwydd.

Mark heading up toward the Cefn Cyfarwydd ridge

Pen Llithrig y Wrach rising above Llyn Cowlyd

The bwlch was positioned in a flat-bedded bog and I was thankful for my chose of footwear, which for winter walking in the climate and conditions that lovely Wales sometimes offers are a must.

Gathering data at the critical bwlch of Pt. 504.7m (SH 744 624)

Once five minutes of data were gathered I followed Aled and Mark through the heathery surrounds to the hill’s summit, which consists of three potential high points, with two of these were judged to be candidates for the true summit, they were duly surveyed.

Gathering data at the first position surveyed for the summit of Pt. 504.7m

Gathering data at the second position surveyed for the summit of Pt. 504.7m

By now the grey overhead conditions that had followed immediately after the rain had been replaced by blue sky and a chilling afternoon strong breeze.  During the two summit surveys Mark headed down to investigate the area of the critical bwlch for Cefn Cyfarwydd.  This hill now shone in the afternoon light, a bulk of a hill that looked from this vantage point to easily have the required minimum 30m of drop to qualify for Dewey status.

As I stood upon the summit that had just been Trimbled long shadows cast out against the heather at my feet with Cefn Cyfarwydd beyond.  Once the Trimble was packed away I followed Aled through the rough heather toward a welcoming path that eased passage down toward the area of the connecting bwlch.

Cefn Cyfarwydd

This bwlch consisted of two lines of land that curved round an intermediary heathery bump, whilst Mark succumbed to the pleasures of lying in copious amounts of heather, Aled and I assessed the land and decided that two surveys were required, one from either side of the heathery bump with the placement of the Trimble nearer Cefn Cyfarwydd our favoured position for the critical bwlch of this hill.

Gathering data at the critical bwlch of Cefn Cyfarwydd

It was now 4.30pm and as I followed Mark and Aled up toward the summit of Cefn Cyfarwydd banks of cloud had pushed in from the south-west and any remaining blue sky was now positioned to our north over the sea.

Moel Siabod (L), Creigiau Gleision (centre) and Pen Llithrig y Wrach (R)

It felt good to be on this hill determining its drop after comparing its bwlch spot height against the 5m contouring on OS Maps.  Map research can often give the prospect for interesting survey results and my inclination before processing the Cefn Cyfarwydd data is that it will have sufficient drop to qualify for Dewey status.

As I approached the top of Cefn Cyfarwydd Aled and Mark were standing on its high point which consists of a slight heathery rise amongst more heather.  The Trimble was soon positioned on Aled’s rucksack to give it elevation above its immediate surrounds, the measurement offset noted and the 0.1m accuracy level before data should be logged was soon attained, I now waited for the allotted five minutes of data to be gathered and stored.

Gathering data at the summit of Cefn Cyfarwydd

All that remained was the walk down the hill on what proved to be a good path that led on to the narrow lane which culminated at the continuation of the track leading toward Mark’s car which was parked close to Llyn Cowlyd.

The walk back

As I sauntered toward the car the wind whipped down the valley and the landscape looked stunning in the dusk light.  I slowly plodded my way back on the track happy to be out in such a place. 



Survey Result:



Cribau

Summit Height:  501.9m (converted to OSGM15)

Summit Grid Reference:  SH 73264 64129

Bwlch Height:  487.3m (converted to OSGM15)

Bwlch Grid Reference:  SH 73056 63919

Drop:  14.6m (Uchaf reclassified to 500m Sub-Uchaf)

Dominance:  2.90%





Pt. 504.7m

Summit Height:  504.7m (converted to OSGM15)

Summit Grid Reference:  SH 74482 62452

Bwlch Height:  491.4m (converted to OSGM15)

Bwlch Grid Reference:  SH 74150 62406

Drop:  13.3m (Uchaf deletion)

Dominance:  2.64%





Cefn Cyfarwydd

Summit Height:  501.7m (converted to OSGM15)

Summit Grid Reference:  SH 75201 63067

Bwlch Height:  471.0m (converted OSGM15)

Bwlch Grid Reference:  SH 74708 62751

Drop:  30.7m (500m Sub-Twmpau reclassified to 500m Twmpau) (500m Double Sub-Pedwar reclassified to 500m Sub-Pedwar) (Dewey addition)

Dominance:  6.11%











Monday, 20 May 2019

Mapping Mountains – Hill Reclassifications – 100m Twmpau


Mynydd y Castell (SS 806 864) – 100m Sub-Twmpau reclassified to 100m Twmpau

There has been confirmation of a reclassification to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Mynydd y Castell

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

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 name of the hill is Mynydd y Castell, and it is adjoined to the Cymoedd Morgannwg group of hills, which are situated in the central part of South Wales (Region C, Sub-Region C2), and it has the A48 road and the M4 motorway to its south-west and the town of Aberafan towards its north-west and the village of Y Pîl (Pyle) towards its south south-east.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was included in the Hills to be surveyed sub list that accompanied the main P30 list, as it was thought at that stage not to meet the criteria used in this list. 

When 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 an estimated c 38m of drop, based on an estimated summit height of c 121m and an estimated bwlch height of c 83m, with both heights based on interpolation of 10m contouring on the Ordnance Survey 1:25,000 Explorer map.

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

The drop value for this hill was re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website became available online; this mapping is entitled the Interactive Coverage Map.  Although this mapping still has no summit spot height it does have an 83m bwlch spot height and the advantage of 5m contouring which enabled a better interpolation of the drop value, and the hill was subsequently listed with c 37m of drop.

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website

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 confirmation of the reclassification of Mynydd y Castell to 100m Twmpau status is due to LIDAR analysis, resulting in a 120.1m summit height and an 83.8m bwlch height, with these values giving this hill 36.2m of drop which is sufficient for it to be classified as a 100m Twmpau.


The full details for the hill are:

Group:  Cymoedd Morgannwg

Name:  Mynydd y Castell

OS 1:50,000 map:  170

Summit Height:  120.1m (LIDAR, natural ground)

Summit Grid Reference:  SS 80681 86460 (LIDAR, natural ground)

Bwlch Height:  83.8m (LIDAR)

Bwlch Grid Reference:  SS 80753 86593 (LIDAR)

Drop:  36.2m (LIDAR)


Myrddyn Phillips (May 2019)