Myrddyn Phillips - Mapping Mountains: Mapping Mountains – Summit Relocations

Sunday, 13 August 2017

Mapping Mountains – Summit Relocations – Y Pellennig –The Remotest Hills of Wales

Y Pellennig –The Remotest Hills of Wales – Summit Relocations

Y Pellennig –The Remotest Hills of Wales comprise all Welsh hills whose summit is 2.5km or more from the nearest paved public road and which have a minimum 15m of drop, with the Change Register to this list available via Mapping Mountains.

The list is co-authored by Myrddyn Phillips and Aled Williams and the posts that have appeared on Mapping Mountains detailing the summit relocations to this list appear below presented chronologically in receding order.

Mapping Mountains - Summit Relocations - Y Pellennig - The Remotest Hills of Wales

Foel Fras (SH 696 681) - 7th summit relocation

Significant Height Revisions post for Foel Fras

There has been a Summit Relocation to a hill that is listed in the Y Pellennig – The Remotest Hills of Wales, Welsh Highlands – Uchafion Cymru and 900m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Leica RX1250 survey conducted by Alan Dawson.

Foel Fras (SH 696 681) from the summit of Trwsgl (SH 663 679)

The criteria for the three listings that this summit relocation 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 co-authored by Myrddyn Phillips and Aled Williams and is available as a downloadable e-booklet or print-booklet version on Mapping Mountains Publications with the up-to-date master list available on Mapping Mountains to download in Google Doc format.

Y Pellennig - The Remotest Hills of Wales by Myrddyn Phillips and Aled Williams

Welsh Highlands – Uchafion Cymru – Welsh hills at or above 500m in height with 15m minimum drop, with an accompanying sub list entitled the Welsh Highland Subs, the criteria for which is all Welsh hills at or above 500m in height with 10m or more and below 15m of drop. This list is authored by Myrddyn Phillips and Aled Williams with the Introduction to the list published on Mapping Mountains in November 2015 and the latest update relating to the list published on Mapping Mountains in January 2023.

Welsh Highlands - Uchafion Cymru by Aled Williams and Myrddyn Phillips

900m Twmpau - Welsh hills at or above 900m and below 1000m in height with 30m minimum drop, with an accompanying sub list entitled the 900m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 900m and below 1000m 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 list is authored by Myrddyn Phillips and is available to download in Google Doc format from Mapping Mountains.

900m Twmpau by Myrddyn Phillips

The name the hill is listed by is Foel Fras and it is adjoined to the Carnedd Llywelyn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A55 road to its north-west, the A5 road to its south-west and the B5106 and A470 roads to its east, and has the town of Bethesda towards the west south-west.

When the original list that later became known as the Welsh Highlands – Uchafion Cymru was first compiled, this hill was listed with 58m of drop, based on the 942m summit spot height adjoined to a triangulation pillar positioned at SH 69652 68173 that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and the 884m bwlch spot height that appears on the Ordnance Survey 1:25,000 Explorer map.

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

However, the summit area of this hill is rocky and includes a number of substantial upright rock spikes. One of the earliest Abney Level surveys to ascertain the high point of this hill was conducted in 2011 by Graham Jackson. This survey concluded that a rock spike approximately 55 metres south-wesward of the trig pillar is the highest point of this hill.

This rock spike was subsequently surveyed by Alan Dawson using the Leica RX1250, resulting in a 944.1m summit height positioned at SH 69611 68118, and this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation, within a different map contour, to a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is considered a relatively recent man-made construct, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist.

The Leica RX1250 gathering data at the summit of Foel Fras (SH 696 681). Photo: Alan Dawson

Therefore, the new listed summit height of this hill is 944.1m and this is positioned at SH 69611 68118 and this was derived from a Leica RX1250 survey, this position is approximately 55 metres south-westward from where the triangulation pillar is positioned and importantly it is positioned to a different feature.

The full details for the hill are:

Group: Carnedd Llywelyn

Name: Foel Fras

OS 1:50,000 map: 115

Summit Height: 944.1m (converted to OSGM15, Leica RX1250)

Summit Grid Reference (New Position): SH 69611 68118 (Leica RX1250)

Bwlch Height: 881.3m (converted to OSGM15, Leica RX1250)

Bwlch Grid Reference: SH 68799 66515 (Leica RX1250)

Drop: 62.8m (Leica RX1250)

Remoteness: 3.975km

Myrddyn Phillips and Aled Williams (August 2024)

Mapping Mountains - Summit Relocations - Y Pellennig - The Remotest Hills of Wales

The Head (SM 731 046) - 6th summit relocation

There has been a Summit Relocation to a hill that is listed in the 30-99m Twmpau, Y Trechol – The Dominant Hills of Wales and Y Pellennig – The Remotest Hills of Wales, with the summit height and its location, the drop, dominance, remoteness and status of the hill prompted by detail produced by Joe Nuttall in his surface analysis programme (JNSA).

The criteria for the three listings that this summit relocation applies to are:

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

30-99m Twmpau by Myrddyn Phillips

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. The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format.

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

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 15m minimum drop. The list is co-authored by Myrddyn Phillips and Aled Williams and is available as a downloadable e-booklet and print-booklet version on Mapping Mountains Publications with the up-to-date master list available to download on the Mapping Mountains site in Google Doc format.

Y Pellennig - The Remotest Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is The Head, and it is adjoined to the Garn Fawr group of hills which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned on the island of Skokholm which is positioned to the south-west of the Pembrokeshire coast.

When the original 30-99m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the main P30 list with a 55m summit height positioned at SM 730 047, with an accompanying note stating; Height from 1:10000 map, details from David Purchase.

After 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 56m summit height and drop, based on interpolation of its largest 55m uppermost contour positioned at SM 72969 04698. The summit position was subsequently and slightly amended to SM 72970 04701 from detail that appeared on the Hill Bagging website.

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

However, it was not until Joe Nuttall developed his surface analysis programme that the details of this hill could be analysed via the OS Terrain product. The height produced by the surface analysis programme is 55.0m and this is positioned at SM 73112 04672, and this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation, within a different map contour, to a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is judged to be a relatively recent man-made construct, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist.

Therefore, the height produced by the surface analysis programme developed by Joe Nuttall is 55.0m and is positioned at SM 73112 04672, this position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and is positioned to a different 55m contour and approximately 42 metres eastward from where the previously listed summit is positioned.

The full details for the hill are:

Group: Garn Fawr

Name: The Head

OS 1:50,000 map: 157

Summit Height: 55.0m (JNSA)

Summit Grid Reference (New Position): SM 73112 04672 (JNSA)

Bwlch Height: N/A (island)

Bwlch Grid Reference: N/A (island)

Drop: 55.0m (JNSA)

Dominance: 100.00% (island)

Remoteness: 5.21km (JNSA)

Myrddyn Phillips and Aled Williams (May 2024)

Mapping Mountains - Summit Relocations - Y Pellennig - The Remotest Hills of Wales

Esgair Llyn Du (SN 769 620) - 5th summit relocation

Survey post for Esgair Llyn Du

There has been a Summit Relocation to a hill that is listed in the Welsh Highlands – Uchafion Cymru and Y Pellennig – The Remotest Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Aled Williams.

Esgair Llyn Du (SN 769 620)

The criteria for the two listings that this summit relocation applies to are:

Welsh Highlands - Uchafion Cymru by Aled Williams and Myrddyn Phillips

Y Pellennig - The Remotest Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Esgair Llyn Du and it is adjoined to the Esgair Wen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with a minor road to its north-west and south, and has the small community of Pontrhydfendigaid towards the north-west and the town of Tregaron towards the west south-west.

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

When the 1^st edition of the Y Pellennig – The Remotest Hills of Wales was published by Europeaklist in April 2015, this hill was listed with 3.075km of remoteness and 20m of drop, based on the 534m summit spot height positioned at SN 767 617 and the 514m bwlch spot heights that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map, with this mapping giving two positions of equal height for the bwlch.

Extract from the interactive mapping hosted on the WalkLakes website

The Ordnance Survey Vector Map Local hosted on the Geograph website gave the higher spot height to the middle of three larger 530m map contour rings, with the southerly and middle ring contours subsequently surveyed with the Trimble GeoXH 6000. However, the interactive mapping hosted on the WalkLakes website indicates that the most northerly of these is the higher.

The Trimble GeoXH 6000 set-up position at the southerly of the three tops

The Trimble GeoXH 6000 set-up position at the central of the three tops

At the northerly of the three tops and the summit of Esgair Llyn Du

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 results from these surveys are given below:

LIDAR for northerly summit: 532.849m at SN 76930 62044

LIDAR for central summit: 532.729m at SN 76768 61773

Trimble GeoXH 6000 for central summit: 532.552m at SN 76770 61772

LIDAR for southerly summit: 532.020m at SN 76691 61642

Trimble GeoXH 6000 for southerly summit: 531.914m at SN 76691 61642

The 532.8m summit height produced by LIDAR analysis and its position in relation to the previously listed summit comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies to when the high point is positioned in a different field, to a different feature such as a conifer plantation, within a different map contour, a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is considered a relatively recent man-made construct, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist.

LIDAR image of Esgair Llyn Du (SN 769 620)

LIDAR summit image of Esgair Llyn Du (SN 769 620)

Therefore, the summit height produced by LIDAR analysis is 532.8m and this is positioned at SN 76930 62044. This position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, but a 532m spot height appears in this position on the interactive mapping hosted on the WalkLakes website and is approximately 440 metres north-eastward from where the originally listed summit is positioned and approximately 300 metres north-eastward from where the previously listed summit is positioned, resulting in its remoteness being amended from 3.075km to 2.925km.

The full details for the hill are:

Group: Esgair Wen

Name: Esgair Llyn Du

OS 1:50,000 map: 146, 147

Summit Height: 532.8m (LIDAR)

Summit Grid Reference: SN 76930 62044 (LIDAR)

Bwlch Height: 513.8m (LIDAR)

Bwlch Grid Reference: SN 76942 61196 (LIDAR)

Drop: 19.0m (LIDAR)

Remoteness: 2.925 km

Myrddyn Phillips and Aled Williams (November 2023)

Mapping Mountains - Summit Relocations - Y Pellennig - The Remotest Hills of Wales

Ynys Bery (SM 701 219) - 4th summit relocation

There has been confirmation of the higher summit of a twin map topped hill that is being detailed under the Summit Relocations heading, and the hill is listed in the 30-99m Twmpau, Y Trechol – The Dominant Hills of Wales and Y Pellennig – The Remotest Hills of Wales, with the summit height and its location confirmed by LIDAR analysis conducted by Aled Williams.

LIDAR image of Ynys Bery. 1m contour (black), 10m contour (red) and sea level (yellow)

The criteria for the three listings that this summit relocation 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.

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 3^rd December 2015.

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-booklet or print-booklet version on Mapping Mountains Publications with the up-to-date master list available on the Mapping Mountains site in Google Doc format.

The name of the hill is Ynys Bery and as its name implies it is an island, 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 is positioned to the south of the larger Ynys Dewi.

This hill was originally listed in the Welsh 30-99m P30 hills published on Geoff Crowder’s v-g.me website, with a 71m summit height and an accompanying note stating; Two tops of same height. The 71m summit height appears as a spot height given to two separate tops on the Ordnance Survey 1:25,000 Explorer map with these positioned at SM 70058 21863 and SM 70183 21965.

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 reassessed when the Ordnance Survey Vector Map Local hosted on the Geograph website became available online; this map is entitled the Interactive Coverage Map and the two twin map heighted 71m summits were again shown.

LIDAR analysis confirms that the north-easterly of these two summits is the higher and this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies to any listed hill whose summit meets the following criteria; where there are a number of potential summit positions within close proximity and the highest point is not where previously given, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist, or when the summit of the hill is in a different field compared to where previously given, or when the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary that is judged to be a relatively recent man-made construct. 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 relocations.

Therefore, the summit height produced by LIDAR analysis is 72.0m and is positioned at SM 70182 21959, this position is given a 71m spot height on the Ordnance Survey 1: 25,000 Explorer map and is approximately 150 metres north-east from where the other twin map heighted summit is positioned which LIDAR analysis gives as 71.9m at SM 70056 21859.

The full details for the hill are:

Group: Carn Llidi

Name: Ynys Bery

OS 1:50,000 map: 157

Summit Height: 72.0m (LIDAR)

Summit Grid Reference (new position): SM 70182 21959 (LIDAR)

Bwlch Height: N/A, sea level

Bwlch Grid Reference: N/A, sea level

Drop: 72.0m (LIDAR)

Dominance: 100.00% (LIDAR)

Remoteness: 3.925 km

Myrddyn Phillips and Aled Williams (July 2019)

Mapping Mountains - Summit Relocations - Y Pellennig - The Remotest Hills of Wales

Foel Cedig (SH 981 283) - 3th summit relocation

Survey post for Foel Cedig

There has been a Summit Relocation to a hill that is listed in the Yr Uchafion, the 600m Twmpau and Y Pellennig – The Remotest Hills of Wales with the summit height, its location and drop of the hill being confirmed by a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips with the bwlch surveyed on the 19^th October 2016 and the summit on the 16^th August 2018.

Foel Cedig (SH 981 283) on the left and Cyrniau Nod (SH 988 279) on the right

The criteria for the three listings that this summit relocation applies to are:

Yr Uchafion – Welsh hills at or above 500m in height that have 15m minimum drop. The list is co-authored by Myrddyn Phillips and Aled Williams, with the Introduction to this list appearing on Mapping Mountains on the 4^th November 2015.

600m Twmpau – Welsh hills at or above 600m and below 700m in height that have 30m minimum drop, with an accompanying sub category entitled the 600m Sub-Twmpau consisting of all Welsh hills at or above 600m and below 700m in height that have 20m or more and below 30m of drop. With the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. The list is authored by Myrddyn Phillips.

The name of the hill is Foel Cedig, and it is adjoined to the Y Berwyn range of hills, which are situated in the south-eastern part of North Wales (Region A, Sub-Region A4), and is positioned to the north of Llyn Efyrnwy (Lake Vyrnwy) and has the town of Y Bala towards the north-west.

As the summit of the hill is a part of designated open access land it can be approached from various directions. However, the easiest approach is from the north-west where a track contours the moorland and it is only a short walk from this point to the summit of the hill.

When the qualifying summit for the Yr Uchafion, 600m Twmpau and Y Pellennig – The Remotest Hills of Wales was first listed it was given to the hill named Cyrniau Nod which is positioned at SH 988 279 and listed with a 666m summit height which appears as a spot height on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. Whilst the summit of Foel Cedig which is positioned at SH 981 283 is given a 666m height on these same maps.

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

As the surveying technique that produced these two spot heights has a +/- 3m margin of uncertainty applied to it, it meant that Foel Cedig could in fact be higher than Cyrniau Nod, therefore both hills were surveyed with the Trimble GeoXH 6000.

The results from these two surveys are given below:

Foel Cedig: 667.417m at SH 98170 28327

Cyrniau Nod: 666.207m at SH 98847 27920

Since the qualifying summit has been relocated to Foel Cedig this has also affected the lists of Marilyns, Humps, Simms, Hewitts, Nuttalls and Tumps, with Alan Dawson as list author of the Marilyns, Simms and Hewitts having accepted this result the other list authors soon followed suit.

A subsequent Leica GS15 survey conducted by John Barnard and Graham Jackson on the 15^th September 2018 resulted in the following:

Foel Cedig: 667.479m at SH 98170 28327

Cyrniau Nod: 666.234m at SH 98847 27918

Data sets of ten and eleven minutes were collected with the Trimble GeoXH 6000, whilst 122 and 121 minute data sets were collected with the Leica GS15.

The Trimble GeoXH 6000 gathering data at the summit of Foel Cedig with Cyrniau Nod in the background

The 667.4m summit height produced by the Trimble GeoXH 6000 survey and its position in relation to that of Cyrniau Nod comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The Trimble GeoXH 6000 gathering data at the summit of Cyrniau Nod with Foel Cedig in the background on the left

The summit height produced by the Trimble GeoXH 6000 survey is 667.4m and is positioned at SH 98170 28327, this position is approximately 800 metres north-west from where the old listed summit of Cyrniau Nod is positioned.

The full details for the hill are:

Group: Y Berwyn

Name: Foel Cedig

OS 1:50,000 map: 125

Summit Height: 667.4m (converted to OSGM15)

Summit Grid Reference (new position): SH 98170 28327

Bwlch Height: 487.4m (converted to OSGM15)

Bwlch Grid Reference: SH 94458 27324

Drop: 180.0m (converted to OSGM15)

Remoteness: 3.200 km

For details on the survey that relocated the summit of this hill

Myrddyn Phillips and Aled Williams (January 2019)

Mapping Mountains - Summit Relocations - Y Pellennig - The Remotest Hills of Wales

Esgair Cerrig (SN 952 432) - 2nd summit relocation

Survey post for Esgair Cerrig

Significant Name Changes post for Esgair Cerrig

There has been a Summit Relocation initiated by LIDAR data analysed by Aled Williams and confirmed by a survey with the Trimble GeoXH 6000, to the listings of Y Pellennig and Y Pedwarau, with the survey that resulted in this summit relocation taking place on the 28^th December 2016 in good, clear and bright conditions.

The two lists that this summit relocation affects are:

Y Pellennig - The Remotest Hills of Wales, with the criteria being all hills in Wales whose summit is 2.5km or more from the nearest paved public road that have a minimum 15m of drop. This list is co-authored by Myrddyn Phillips and Aled Williams.

Y Pedwarau, with the criteria being all hills in Wales at and above 400m and below 500m in height that have a minimum 30m of drop. This list is co-authored by Myrddyn Phillips and Aled Williams.

The name of the hill is Esgair Cerrig and this was derived from local enquiry (see Significant Name Changes) and access to it is restricted due to it being positioned within the confines of the Sennybridge Artillery Range Training Area. The hill is situated in the Mynydd Epynt range, which is placed in the south-eastern part of Mid and West Wales (Region B, Sub-Region B2), and the hill is positioned above the small community of Llangamarch (Llangammarch Wells) to its north north-west and the small town of Llanwrtyd (Llanwrtyd Wells) to its west north-west.

This hill’s summit position was previously given as SN 956 435 and this is where the current 456m spot height appears on Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps. However, prior to the survey with the Trimble GeoXH 6000 this hill’s summit was analysed using LIDAR data by Aled Williams. LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

Aled’s analysis of LIDAR data gives the hill the following details:

Esgair Cerrig

Summit Height: 456.3m

Summit Grid Reference: SN 95226 43298

The analysis of LIDAR data pinpointed this hill’s position and its height was confirmed with the Trimble survey:

Esgair Cerrig

Summit Height: 456.4m (converted to OSGM15)

Summit Grid Reference: SN 95224 43297

Therefore the position of the relocated summit is at SN 95224 43297 and is featureless ground consisting of grass interspersed with reed grass beside a bomb crater, this position is within the uppermost 450m ring contour on Ordnance Survey maps although no spot height is given to it, the relocated summit is approximately 490 metres south-westward from where the previously listed summit is positioned.

The full details for the hill are:

Cardinal Hill: Mynydd Epynt

Summit Height: 456.4m (converted to OSGM15)

Name: Esgair Cerrig

OS 1:50,000 map: 147, 160

Summit Grid Reference (New Position): SN 95224 43297

Drop: 35.6m (converted to OSGM15)

The Trimble GeoXH 6000 gathering data at the summit of Esgair Cerrig, with the old position of the summit in the centre background of this photograph

For details on the survey that relocated the summit of this hill.

Myrddyn Phillips and Aled Williams (January 2017)

Mapping Mountains - Summit Relocations - Y Pellennig - The Remotest Hills of Wales

Bryn Llwyd (SN 835 920) - 1st summit relocation

First survey post for Bryn Llwyd

Second survey post for Bryn Llwyd

Hill Reclassifications post for Bryn Llwyd

Significant Name Changes post for Bryn Llwyd

There has been a Summit Relocation initiated by a survey with the Trimble GeoXH 6000 to the listings of Y Pellennig, Yr Uchafion and 500m Twmpau, with the survey that resulted in this summit relocation being conducted on the 5^th and 13^th May 2016.

The three lists that this summit relocation affects are:

Y Pellennig - The Remotest Hills of Wales, with the criteria being all hills in Wales whose summit is 2.5km or more from the nearest paved public road that have a minimum 15m of drop. This list is co-authored by Myrddyn Phillips and Aled Williams.

Yr Uchafion, this is the working title for a list that takes in all hills in Wales at and above 500m in height that have a minimum 15m of drop. This list is co-authored by Myrddyn Phillips and Aled Williams.

500m Twmpau (thirty welsh metre prominences and upward), with the criteria being all Welsh hills at or above 500m and below 600m in height that have a minimum 30m of drop. This list is authored by Myrddyn Phillips.

As the hill only entered the ranks of Pellennig hills due to this survey this listing of hills is being included within this Summit Relocations heading.

The survey was conducted in the Pumlumon range of hills over two beautiful sunny days, with the hill situated mid-way between the towns of Machynlleth to its north-west and Llanidloes to its south-east.

The name of the hill where the summit has been re-located to is Bryn Llwyd (SN 835 920) and the name of the hill where the summit has been re-located from is Bryn yr Ŵyn (SN 839 925). Both summits and respective bylchau were surveyed with the Trimble with their summits being connected by a bwlch that is only 9.9m below the summit height of Bryn yr Ŵyn and 11.4m below the summit height of Bryn Llwyd.

The summits of both hills possess a small uppermost 500m ring contour on Ordnance Survey maps with no adjoined spot height, with the uppermost ring contour for Bryn Llwyd being the larger.

The critical bwlch for the higher of these hills in positioned to the south-west and to my knowledge their drop has only been surveyed on three occasions, once using a basic levelling survey (BLS) method, and the other two using the Trimble GeoXH 6000. The results from each survey appear below:

Bryn Llwyd: summit to critical bwlch, 102.5ft (31.2m) drop (BLS), 30.3m drop (Trimble).

Bryn yr Ŵyn: summit to connecting bwlch with Bryn Llwyd, 42.5ft (13.0m) drop (BLS), 9.9m drop (Trimble).

I conducted the basic levelling survey in July 2000 and sent the details to Michael Dewey. Michael assessed the information and decided to include Bryn yr Ŵyn in his list to The 500-Metre Tops of England and Wales. The margin of uncertainly associated with the BLS method is within the error tolerance of the result, and I have wanted to re-visit and survey both hills and produce accurate absolute heights for each, ever since. Their heights as surveyed by the Trimble GeoXH 6000 appear below:

Bryn Llwyd 501.4m (converted to OSGM15) summit at SN 83574 92022 (average of four surveys conducted over two days)

Bryn yr Ŵyn 499.9m (converted to OSGM15) summit at SN 83919 92571 (average of five surveys conducted over two days)

Therefore the position of the relocated summit is at SN 83574 92022 and it consists of grass atop an ancient mound. The summit area and the hill itself has relatively easy underfoot conditions and consists of moor grass with a path leading from the critical bwlch to the south-west toward the connecting bwlch with Bryn yr Ŵyn.

This re-located summit position is not given a spot height on current Ordnance Survey maps and it is approximately 660 metres south south-westward from the previously listed summit position.

The full details for the hill are:

Cardinal Hill: Pumlumon Fawr

Summit Height: 501.4m (converted to OSGM15, and average of four summit surveys)

Name: Bryn Llwyd

OS 1:50,000 map: 135, 136

Summit Grid Reference (New Position): SN 83574 92022

Drop: 30.3m (converted to OSGM15)

The Trimble GeoXH 6000 gathering data at the summit of Bryn Llwyd, with the summit of Bryn yr Ŵyn on the right and in the background of this photograph

For details on the 1^st Trimble survey and the 2nd Trimble survey that relocated the summit of this hill.

Myrddyn Phillips and Aled Williams (May 2016)

Sunday, 13 August 2017

Mapping Mountains – Summit Relocations – Y Pellennig –The Remotest Hills of Wales

No comments: