Monday, 17 June 2019

Mapping Mountains – Hill Reclassifications – Hewitts


Calf Top (SD 664 856) – SubHewitt reclassified to Hewitt

This is one in a series of retrospective Hill Reclassification posts that detail hills whose status has altered in the listing of the English Hewitts (an acronym for Hill in England, Wales or Ireland over Two Thousand feet high).  These reclassification posts will give details of hills where I have had direct association with their change of status, and they will tie in with a forthcoming Change Register giving detail to this list and its alterations since first publication.

The listing of English Hewitts was published in booklet format by TACit Tables in June 1997 and entitled The Hewitts and Marilyns of England.  This list evolved out of The Absolute Summits of England and Wales which were known as the Sweats (an acronym for Summits in Wales and England Above Two-thousand FEET) and which was published by Cicerone Press in 1992 in the book entitled The Relative Hills of Britain.  The list compiler for the Hewitts and the preceding Sweats is Alan Dawson.

When the English Hewitts list was published in booklet format there were 178 qualifying hills listed with their criteria being any English hill at or above 2000ft (609.6m) in height with 30m minimum drop, accompanying the main list are two sub category’s entitled SubHewitts, with the two sets of criteria being any English hill at or above 600m and below 2000ft (609.6m) in height that have a minimum drop of 30m and any English hill at or above 2000ft (609.6m) in height with 20m or more and below 30m of drop.

The Hewitts and Marilyns of England by Alan Dawson

The details for the hill reclassification appear below:

The name of the hill is Calf Top, and it is situated in the Central Pennines of northern England, and is positioned with the A683 and the M6 roads to its west, and has the small town of Sedbergh towards the north and the small community of Barbon towards the south-west.

Calf Top (SD 664 856) from Castle Knott

Prior to this hill’s reclassification to Hewitt status it was listed as a SubHewitt with 312m of drop based on the 609m summit spot height that appeared on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps of the day and a col height of 297m.

As its 609m summit spot height was near the benchmark height of 2000ft (609.6m) it was prioritised for a GNSS survey and this took place on the 15th April 2010.  The hill was surveyed by John Barnard, Graham Jackson and Myrddyn Phillips using a Leica 530 and two hours of data were gathered, resulting in a summit height at that time of 609.61m.

Gathering data with the Leica 530 during the first summit survey of Calf Top

As this result was so close to the benchmark height of 2000ft (609.6m) it was decided to re-visit and gather a further four hours of data.  The second survey was conducted on the 20th May 2010 by John Barnard, Graham Jackson and Myrddyn Phillips using a Leica 530, resulting in a summit height at that time of 609.62m.  As the results from these surveys were so close to the 2000ft / 609.6m height the two data sets were sent to Ordnance Survey and were processed using their Bernese software, resulting in a summit height of 609.58m.

Gathering data with the Leica 530 during the second summit survey of Calf Top

This height was reassessed in August 2016 when Ordnance Survey adopted their new OSTN15 / OSGM15 model which replaced their OSTN02 / OSGM02 model.  The adoption of the OSTN15 / OSGM15 model increased the known height of hills in England by an average of 2cm - 4cm, and in the case of Calf Top this resulted in its known accurate height increasing to 609.61m, which is higher than the minimum 2000ft (609.6) height required for Hewitt status.

The reclassification of this hill from Sub-Hewitt to Hewitt status was accepted by the list author and its new classification augmented in to the listing of the Hewitts in August September 2016.



The full details for the hill are:

Name:  Calf Top

OS 1:50,000 map:  98

OS 1:25,000 map:  2

Summit Height:  609.61m (converted to OSGM15)

Summit Grid Reference:  SD 66450 85624

Col Height:  297m

Col Grid Reference:  SD 682 867

Drop:  313m


Myrddyn Phillips (June 2019)















Sunday, 16 June 2019

Mapping Mountains – Significant Height Revisions – 100m Twmpau


Bryn Bach (SS 903 875)

There has been a Significant Height Revision to a hill that is now 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 Bryn Bach

The criteria for the list that this height revision 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 Bryn Bach, and this was derived from the Ordnance Survey One-Inch ‘Old Series’ map and it is this name that the hill is now listed by, 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 is positioned with the A4063 road and the Afon Llynfi to its south-west and the A4064 road and the Afon Garw to its south-east, and has the small community of Betws towards the south. 

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. 

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 31m of drop, based on an estimated summit height of c 164m and an estimated bwlch height of c 133m, 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 details for this hill were 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.  This mapping gives a 164m summit spot height and as it has 5m contour intervals it enabled a better assessment for an interpolated value for the height of the bwlch.  It also has a 133m spot height at a junction of roads at the area of this hill’s bwlch, with interpolation favouring a different position for the critical bwlch and an estimated height of c 133m, with these values giving this hill c 31m 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 summit height produced by LIDAR analysis is 167.0m, this is not a substantial revision compared to some revised heights, but it does come within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 Explorer map is being prioritised in favour of the 1:50,000 Landranger map for detailing these revisions.

Therefore, this hill’s new listed summit height is 167.0m and this was produced by LIDAR analysis, this is 3m higher than the 164m spot height that appears on the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map.


ills of Wales, and are reproduced below@
The full details for the hill are:

Group:  Cymoedd Morgannwg

Name:  Bryn Bach

OS 1:50,000 map:  170

Summit Height (New height):  167.0m (LIDAR)

Summit Grid Reference:  SS 90364 87431 (LIDAR)
  
Bwlch Height:  135.2m (LIDAR)

Bwlch Grid Reference:  SS 90511 87849 (LIDAR)

Drop:  31.9m (LIDAR)


Myrddyn Phillips (June 2019)




Saturday, 15 June 2019

Mapping Mountains – Hill Reclassifications – Y Pellennig – The Remotest Hills of Wales


Pt. 22.2m (SM 701 226) – Pellennig addition

There has been an addition to the listing of Y Pellennig – The Remotest 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 Aled Williams.

Pt. 22.2m (SM 701 226)

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

Y Pellennig – The Remotest Hills of Wales - Welsh hills whose summit is at least 2.5km from the nearest paved public road and the hill has a minimum 15m of drop, the list is a joint compilation between Myrddyn Phillips and Aled Williams and is available as a downloadable e-bookletor print-booklet version on Mapping Mountains Publications with the up-to-date master list available on the Mapping Mountains site in Google Doc format.

As the authors do not know an appropriate name for this hill either from historic research or local enquiry it is being listed by the point (Pt. 22.2m) notation, and it is adjoined to the Carn Llidi group of hills which are situated in the south-western part of Mid and West Wales (Region B, Sub-Region B4), and it is positioned in a small sheltered bay on the southern side of Ynys Dewi.

This hill was not included when the original list of Pellennig hills was compiled as contemporary Ordnance Survey 1:25,000 Explorer maps do not give it any contour ring.  The lack of contour rings is also applicable to the Ordnance Survey Vector Map Local hosted on the Geograph website which is entitled the Interactive Coverage Map.

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

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

The details for this hill were re-assessed when the OS Maps website became available online.  This is the replacement for OS Get-a-map and has 5m contour intervals.  This mapping gives this hill an uppermost 15m ring contour, but as this hill is adjoined to its southerly counterpart which is already listed as a Pellennig hill by a connecting bwlch higher than 5m it implies that its drop is less than the minimum 15m required for it to be considered for Pellennig status.

Extract from the OS Maps 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.

LIDAR image of Pt. 22.2m; 1m contour (black), 10m contour (red) and sea level (yellow)

Close up LIDAR image of Pt. 22.2m; 1m contour (black), 10m contour (red) and sea level (yellow)

The addition of this hill to Pellennig status is due to LIDAR analysis, resulting in a 22.2m summit height and confirmation that this is also its drop value as the connecting bwlch is below sea level, and with the distance between its summit and the nearest paved public road being 3.400km, it gives this hill sufficient remoteness and drop for Pellennig status.


The full details for the hill are:

Group:  Carn Llidi

Name:  Pt. 22.2m

OS 1:50,000 map:  157

Summit Height:  22.2m (LIDAR)

Summit Grid Reference:  SM 70180 22696 (LIDAR)

Bwlch Height:  N/A, sea level

Bwlch Grid Reference:  N/A, sea level 
  
Drop:  22.2m (LIDAR)

Remoteness:  3.400km


For the additions and deletions to Y Pellennig – The Remotest Hills of Wales reported on Mapping Mountains please consult the following Change Register:




Myrddyn Phillips and Aled Williams (June 2019)


© Crown: CHERISH PROJECT 2019. Produced with EU funds through the Ireland Wales Co-operation Programme 2014-2020. All material made freely available through the Open Government Licence.




Friday, 14 June 2019

Mapping Mountains – Trimble Surveys – Elenydd


10.04.19  Cripiau (SN 798 836), Banc yr Haul (SN 802 828), Pt. 518.7m (SN 802 825), Peraidd Fynydd (SN 811 824), Peraidd Fynydd (SN 809 825), Pt. 547.3m (SN 807 810), Cefn Croes (SN 808 799 [bwlch only SN 806 811]) and Pt. 555.7m (SN 803 810)  

Banc yr Haul (SN 802 828)

I’d been delaying a visit to the forested delights of Peraidd Fynydd for ten years or more, but with only a few remaining Welsh 500m P15s to visit a concerted effort was required to get my total nearer completion, so this hill needed a visit.

By the time I left Eidteddfa Gurig an east wind chilled to the bone and I started walking in what would not go amiss as full winter gear.  Usually walker’s head north from this point to the higher Pumlumon hills, but my destination today was south to open hillsides followed by forestry and ending close to the Cefn Croes wind farm before retracing my inward route back to the comforts of my car.

A steep uphill soon led to the summit of Cripiau and within a few minutes the Trimble was set atop my rucksack and data gathered.  During this process I stood with my back to the wind overlooking the descending westerly lands toward the coast.  Cloud just skimmed the higher Pumlumon tops to my north, but this was soon blown away as that east wind continued.

Gathering data at the summit of Cripiau

My next hill was due south and known locally as Banc yr Haul, I’d visited this hill twice before, each time surveying it.  The first in July 2000 with my old basic levelling staff and the second with Graham Jackson in February 2010 when we line surveyed the hill in winter conditions.

The land between Cripiau and Banc yr Haul undulates and has one or two old fences crossing it; otherwise it is bleak and wonderfully beautiful.  The connecting bwlch was soon Trimbled and I then pressed on to the conically rising summit of Banc yr Haul which is a delight to the eye compared to many of the rounded summits hereabouts.

Gathering data at the critical bwlch of Cripiau

Cripiau from the approach to Banc yr Haul

I had a number of objectives during this walk, the data from the first two hills can be compared to LIDAR analysis conducted by Aled and the second hill’s line survey, whilst there were two 500m P15s that I had not previously visited, the second of which was Peraidd Fynydd with 5m contouring on the OS Maps website showing its westerly top higher than its 547m spot heighted easterly top, I wanted to visit each and if the Trimble behaved itself gather data from their summits.  There were also two hills leading toward the Cefn Croes wind farm with one having been surveyed with my old basic levelling staff many years ago, this is a marginal P15, and both I planned on Trimbling.

Gathering data at the summit of Banc yr Haul

The connecting bwlch of Banc yr Haul was relatively sheltered and its critical point easy to identify and as the Trimble gathered its customary data I stood back out of the wind waiting patiently for the allotted five minutes of data to be stored.

Gathering data at the critical bwlch of Banc yr Haul

Pt. 518.7m (SN 802 825) from the summit area of Banc yr Haul

Ahead lay a steep slope leading to a 519m spot heighted summit which was the first of two 500m P15s I had not previously visited.  Its high point is at a junction of fences with forest butting up against the old fence on its south-western and south-eastern sides, unfortunately for surveying purposes its high point is positioned under a fallen tree and therefore having taken a ten figure grid reference from its summit I positioned the Trimble away from the trees having aligned it with the hill’s high point.  Once data were gathered and stored I headed down its slopes to enter the forest.

The Trimble marks the spot; at the summit of Pt. 518.7m (SN 802 825)

When I entered the trees my memory whizzed back to Graham and I sheltering from the snow in this spot nine years ago as the figures from our line survey were added up.  Today, conditions were more favourable, albeit that east wind still chilled.

The gap in the trees led to a wide sweeping corner on a part of the access track leading to the Cefn Croes wind farm, I was now sheltered from the wind and enjoyed being in the sun.  The connecting bwlch for the 519m map heighted hill is positioned beside the wide sweeping bend of this track and soon the Trimble was atop my rucksack gathering data.

Gathering data at the critical bwlch of Pt. 518.7m

A steady plod soon brought me to where the track continues out of the forest in a south-eastern direction which in time would lead to the high wind turbines, but I now wanted to visit Peraidd Fynydd and opted to take the north-eastward track leading down through the forest to the Nant Garw Mawr.  As I walked down the track luxuriating myself out of the wind I thought that I’d probably suffer in the afternoon sun reclaiming the height I was now loosing.

Beyond the stream the track veered south-eastward and led to felled forestry which rather conveniently has a narrow gravelled path of sorts which leads up to the forest break to the south of the easterly summit of Peraidd Fynydd.  So far everything was relatively easy, the forest break is now open on its southern side and led westward to where felled forestry ends and the conifers begin.  Entering the forest the break continued through the trees and choosing a point to leave it I used the Trimble as a hand-held device to zero in on the high point of the easterly top which consists of a greened area just free of trees and in a small break of its own.  I was hopeful for satellite coverage, and waited a long time before activating the Trimble.  Before leaving I wanted to take another data set but the equipment could not fix on to the minimum of five satellites required before logging can start.

The graveled path leading up through felled forestry toward the summit of Peraidd Fynydd

At the summit of the easterly of the two Peraidd Fynydd tops

Heading through the trees on a compass bearing I soon found myself on the continuation of the forest break that had brought me in to the trees, and opposite a gap in the trees led up the slopes of the westerly top.  Toward the top of the gap I turned right and followed a distinct ridge to its high point.  It was impossible to judge which of these two tops is higher as there is no direct line of site between them, and I had little hope of the Trimble logging on to the minimum of five satellites, let alone gathering data, but I switched it on and left it placed on top of a mound of moss under a tree and continued on the ridge to check if all ground descended from this point, it did.  Retracing my steps to the Trimble I took a few photos of it on the summit and was just about to switch it off and pack it away as it made a sound indicating that it had logged on to five satellites, considering its position I was more than surprised and soon it was beeping away gathering five minutes of data.

The route toward the summit of the westerly of the two Peraidd Fynydd tops


Gathering data at the summit of the westerly of the two Peraidd Fynydd tops

Leaving the summit I retraced my inward route back to the gap and down to the forest ride and followed this to the felled forestry and the narrow gravelled path down to the forest track where I sat on a conveniently placed bale of hay in the sunshine feeling knackered but happy.

Reclaiming height on the forest track back to where it heads toward the Cefn Croes wind farm proved a slow process as the sun warmed proceedings.  My efforts were broken when a vehicle pulled up, I chatted with the driver for five minutes or so, he worked at the wind farm and was pleasant to meet and this gave me the opportunity to recover from my uphill route.

The two tops of Peraidd Fynydd from the access / forest track

As I left the forestry following the continuation of the access track toward the wind farm the next point to survey was the bwlch of a 556m spot heighted hill and its critical point was beside the track.  Once data were gathered and stored I continued on the track as it calved its way through the next hill I wanted to survey with its connecting bwlch to the east of its summit and in a bog.

Gathering data at the critical bwlch of Pt. 555.7m


The Cefn Croes wind farm

I took two data sets on the valley to valley traverse in the bog and stumbled toward the Trimble through small tussocks of bog grass as I checked on its progress, once the allotted data were stored I switched it off and headed in the bog to the next point to survey.  During this I stood back and immersed myself in the scene, these hills are wild affairs, although the wind farm has taken part of this wild quality away, however they are still pleasing.

Gathering data at one of two positions surveyed for the critical bwlch of Pt. 547.3m

As I slowly plodded out of the bog and back through a gate on to the access track and up initial steep slopes to the next summit I felt wiped out and knew that the outward route would have to be taken slowly.  I took data sets from two positions on the summit area of this small hill, one on an attractive grassed area and the other amongst tussocks, with the former my candidate for its high point.

Gathering data at the summit of Pt. 547.3m (SN 807 810)

I only had one survey remaining that I wanted to complete but between me and it lay another bwlch, at the time I didn’t know that this is the critical bwlch connecting to Cefn Croes, but as I was passing I thought I’d better gather data from it.  As the Trimble did its stuff I sat on grass beside a fence under the access track not wanting to move, just wanting to sit and recover.

Gathring data at the critical bwlch of Cefn Croes
Just one summit remained; the 556m spot heighted hill whose connecting bwlch is placed beside the access track and which I had surveyed as I emerged out of the confines of the forest.  Its high point consists of wind- blown grass and as the Trimble gathered its data I sat below it to its west and looked out on the wild surrounds of Llynnoedd Ieuan.

The last survey of the day; at the summit of Pt. 555.7m (SN 803 810)


The last hill of the day; Pt. 555.7m (SN 803 810)

All that remained was the long walk out.  I’d asked the person who had pulled up in his vehicle what time the remaining workers at the wind farm would be heading down the access track to the A44, he told me at about 4.00pm.  Leaving the last summit I walked down its grassed northerly ridge and made it back on to the track at 4.05pm, ate a banana and continued north slowly on the track stopping occasionally in the faint hope of hearing a vehicle approaching.  Suddenly the hum of a red van rounding a corner ignited forlorn hope and I stood, smiled, and pleaded with a thumb in the air for it to stop, the driver smiled and waved and ever so slowly passed, he went so slowly that I thought he was stopping, he wasn’t, and I watched him disappear in a red dot around the next corner.

By now I thought I’d struggle over Banc yr Haul and Cripiau on my way back to Eisteddfa Gurig, so decided to wait at the wide sweeping corner where the gap through the trees gives access toward these two hills, hoping for more vehicles to approach.  Soon one appeared and stopped, the driver offered to drop me at the road but couldn’t take me up to Eisteddfa Gurig as he was already late to pick his daughter up, however he said that a delivery lorry was on its way down the track and the driver was heading toward Welshpool.  I’d waved at this same delivery lorry as it headed toward the wind farm earlier in the afternoon, it soon appeared and the driver took pity on me and within a few minutes I was sitting in the cab.

The driver; Keiron Maddocks enjoyed hill walking so we happily chatted about the hills I had just visited and his various trips to the Lakes and Scotland.  I felt relieved to have got a lift and thanked Keiron a number of times as he drove down the remainder of the track toward the A44.

Keiron saved me a long walk out

I waved him off as he dropped me beside my awaiting car, and duly paid the £5.00 parking fee putting the money through the red doored letter box as instructed.  All that remained was a visit to Eryl and Rita’s in Llanidloes for a couple of hours catch up and a very welcome mug of tea and a lovely meal.       

        

Survey Result:



Cripiau 
 
Summit Height:  510.5m (converted to OSGM15)

Summit Grid Reference:  SN 79838 83644

Bwlch Height:  485.1m (converted to OSGM15)

Bwlch Grid Reference:  SN 79927 83280

Drop:  25.4m

Dominance:  4.98%





Banc yr Haul (significant name change)

Summit Height:  525.6m (converted to OSGM15)

Summit Grid Reference:  SN 80202 82864

Bwlch Height:  495.0m (converted to OSGM15)

Bwlch Grid Reference:  SN 80293 82632

Drop:  30.6m (Trimble GeoXH 6000)  30.6m (Level and Staff line survey)

Dominance:  5.83%





Pt. 518.7m

Summit Height:  518.7m (converted to OSGM15)

Summit Grid Reference:  SN 80249 82542

Bwlch Height:  500.5m (converted to OSGM15)

Bwlch Grid Reference:  SN 80329 82559

Drop:  18.2m (Uchaf status confirmed)

Dominance:  3.51%





Peraidd Fynydd

Summit Height:  547m (spot height prioritised)

Summit Grid Reference:  SN 81166 82428

Bwlch Height:  c 526m (I)

Bwlch Grid Reference:  SN 80853 82417 (I)

Drop:  c 21m 

Dominance:  3.84%





Peraidd Fynydd 
 
Summit Height:  546.7m (converted to OSGM15)

Summit Grid Reference:  SN 80994 82517

Bwlch Height:  c 533m (I)

Bwlch Grid Reference:  SN 81044 82468 (I)

Drop:  13.7m

Dominance:  2.51%





Pt. 547.3m
  
Summit Height:  547.3m (converted to OSGM15)

Summit Grid Reference:  SN 80706 81044

Bwlch Height:  530.9m (converted to OSGM15)

Bwlch Grid Reference:  SN 80823 81083

Drop:  16.4m (Uchaf status confirmed)

Dominance:  3.00%





Cefn Croes  

Summit Height:  573m (Lev)

Summit Grid Reference:  SN 80800 79953 (HH)

Bwlch Height:  529.5m (converted to OSGM15)

Bwlch Grid Reference:  SN 80617 81118

Drop:  43m

Dominance:  7.59%





Pt. 555.7m

Summit Height:  555.7m (converted to OSGM15)

Summit Grid Reference:  SN 80394 81092

Bwlch Height:  531.5m (converted to OSGM15)

Bwlch Grid Reference:  SN 80417 81360

Drop:  24.1m

Dominance:  4.34%