Saturday, 14 March 2020

Change Register - The Marilyns of Wales



Change Register

The Marilyns of Wales


In February 1997 TACit Tables published a booklet entitled The Hewitts and Marilyns of Wales, with a sister booklet to The Hewitts and Marilyns of England being published in June of the same year.  These booklets are two in a series of many that the list author; Alan Dawson, compiled and had published by TACit Tables mainly taking in P30 hills throughout Britain that are 2,000ft (609.6m) and above in height. 

The Marilyns originally appeared as all hills in Britain that have a drop of at least 150m, irrespective of their height.  Accompanying the main list is a sub-list entitled Submarilyns, with the criteria being all hills in Britain that have 140m or more and below 150m of drop. 

The listing of Marilyns was originally published in book format by Cicerone Press in 1992 and entitled The Relative Hills of Britain, its author; Alan Dawson then separated the Welsh and English component parts and published each in the TACit Tables booklets as detailed above.

For those people who have completed an ascent of each listed hill they would have visited all summits in Wales that have a minimum drop of 150m on all sides.  These hills are spread throughout Wales taking in the variety of Snowdonia’s higher summits to the remote and bleak central hills to the old red sandstone giants of the south.  However, Marilyns can also be found in the Bryniau Clwyd range, border country above the Severn Valley and the Mynydd Preseli, each and every hill can leave memories that refresh the soul and body, and for many it is the TACit Table booklet that has taken them on a journey through some of the most beautiful landscape that Britain has to offer.

When the booklet was first published Wales was listed with 156 Marilyns and 27 Submarilyns.  Since these early days the influx of independent surveyors, LIDAR analysis and the diligence of map study have added, deleted and reclassified a number of hills either to Marilyn or Submarilyn status.  But what hills have changed status in this list and who was responsible for their inclusion / exclusion?

The Change Register to The Marilyns of Wales since the TACit Tables publication appears below in receding order under the hill name used by Alan Dawson:



Change Register

The Marilyns of Wales








Moel Oernant    503m at SH 74229 34011 

Prior to this hill being included as a Submarilyn it was listed with an estimated c 138m of drop, based on the 503m summit height which is adjoined to a triangulation pillar and an estimated bwlch height of c 365m based on interpolation of 10m contouring between 360m – 370m.  Its subsequent addition to Submarilyn status is due to contouring on the OS Maps website which has 5m contours at the bwlch area of this hill between 360m – 365m, with an estimated height for the bwlch being c 362m, and when coupled with the 503m summit height these values give this hill c 141m of drop.  These details were sent to the list author; Alan Dawson, on the 2nd August 2019, and notification received via email on the 17th August 2019 that the drop for this hill was likely to exceed that required for Submarilyn status.  Welsh Marilyn total confirmed as 158 and Welsh Submarilyn total increases by one and confirmed as 25.






Mynydd Bwlch-y-Groes    441.7m at SN 86857 35625  

The Trimble GeoXH 6000 gathering data at the summit of Mynydd Bwlch-y-Groes (SN 868 356)

When the TACit Tables booklet to The Hewitts and Marilyns of Wales was published in February 1997 this hill was listed as a Submarilyn with 140m of drop, based on the 442m summit height which is adjoined to a triangulation pillar and appears as a spot height on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and the 302m spot height that appears on the bwlch area on the Ordnance Survey 1:25,000 Explorer map.   Its subsequent deletion from Submarilyn status is due to contouring on the OS Maps website which has 5m contours at the bwlch area of this hill which are between 305m – 310m, with the position of the 302m spot height below the 305m contour line, indicating it is not positioned at the critical point of this bwlch.  These details were sent to the list author; Alan Dawson, on the 8th October 2019, and notification that this hill had been deleted from Submarilyn status was received on the 16th October 2019, with a retrospective Hill Reclassification post published on Mapping Mountains.  The summit of this hill was subsequently surveyed by Myrddyn Phillips and Aled Williams on the 30th December 2019 using a Trimble GeoXH 6000 resulting in a 441.7m height.  Welsh Marilyn total confirmed as 158 and Welsh Submarilyn total decreases by one and confirmed as 24.






Coed y Bwnydd    201.0m at SO 36613 06921 

LIDAR summit image of Coed y Bwnydd (SO 366 069)

This hill was promoted to Submarilyn status due to LIDAR analysis conducted by Myrddyn Phillips, prior to this it was listed by the name of Clytha Hill with an estimated c 68m of drop based on the 196m spot heights that appear on the Ordnance Survey 1:25,000 Explorer map at SO 36831 06935 and the Ordnance Survey Vector Map local hosted on the Geograph website and which is entitled the Interactive Coverage Map at SO 36738 06931, and an estimated bwlch height of c 128m based on interpolation of bwlch contouring between 125m – 130m.  The LIDAR result also affects the adjoining hill named Trostrey Hill (SO 369 051) which has a 199m map height, with LIDAR giving Coed y Bwnydd higher and therefore the respective bylchau positions for each hill are swapped.  The swapping of each bwlch has also altered the drop value for each hill, with the caveat that the drop value for the higher hill; Coed y Bwnydd, has also been amended as there is a road cutting on the hill to hill traverse and its summit comprises an earthen embankment that forms a part of an ancient hill fort, both of which are acceptable to the list author as forming a part of this hill’s drop value.  The LIDAR result for Coed y Bwnydd is 201.0m summit height and 59.4m bwlch height, resulting in 141.6m of drop.  These details were sent to the list author on the 3rd April 2019 and posted on the RHB forum on the 7th April 2019, and notification of this hill’s new status as a Submarilyn was received from Alan Dawson on the 9th April 2019, with a retrospective Hill Reclassification post published on Mapping Mountains.  Welsh Marilyn total confirmed as 158 and Welsh Submarilyn total increases by one and confirmed as 25.






Graig Wen    555.6m at SH 73910 39474 

The Trimble set-up position at the summit of Graig Wen (SH 739 394)

This hill was known to be a potential Submarilyn and was listed with 139m of drop based on the 556m summit height that appears as a spot height on the Ordnance Survey 1:50,000 Landranger map and a bwlch height of 417m that appears as a spot height on the Ordnance Survey 1:25,000 Explorer map.  The summit of the hill was subsequently surveyed by Myrddyn Phillips and Aled Williams on the 1st July 2017 using a Trimble GeoXH 6000 resulting in a 555.6m height.  A revised drop value for this hill was proposed to the list author in October 2017 based on the 555.6m summit height and a revised bwlch height based on bwlch contouring on the OS Maps website between 410m – 415m.  The bwlch of this hill was subsequently surveyed by Myrddyn Phillips on the 23rd December 2017 using a Trimble GeoXH 6000 resulting in a 414.6m height, and when coupled with this hill’s 555.6m summit height these values give this hill 141.0m of drop.  Alan Dawson as list author was notified of this result on the 24th December 2017 and notified his acceptance of this hill as a Submarilyn on the 26th December 2017, with a retrospective Hill Reclassification post published on Mapping Mountains.  Welsh Marilyn total confirmed as 158 and Welsh Submarilyn total increases by one and confirmed as 24.






Mynydd Pencarreg    414.9m at SN 57560 43215 

The summit of Mynydd Pencarreg (SN 575 432) with the Trimble GeoXH 6000 gathering data at the high point

This hill was listed in the TACit Tables booklet as a Submarilyn with an estimated c 141m of drop based on the 415m summit height that is adjoined to a triangulation pillar and which appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated bwlch height of c 274m based on interpolation of 10m contouring between 270m – 280m.  Its deletion from Submarilyn status with a revised drop of c 139m was instigated by Chris Crocker and agreed by the list author in August 2013.  The bwlch height of this hill was subsequently ascertained by LIDAR analysis conducted by Aled Williams, and its summit later surveyed by Myrddyn Phillips on the 31st July 2018 using a Trimble GeoXH 6000, resulting in a 414.9m summit height and a 276.2m bwlch height, with these values giving this hill 138.7m of drop and confirming its deletion from Submarilyn status.  Welsh Marilyn total confirmed as 158 and Welsh Submarilyn total decreases by one and confirmed as 23.






Middleton Hill    205.1m at SN 14646 11773 

The summit of Middleton Hill (SN 146 117)

When the TACit Tables booklet to The Hewitts and Marilyns of Wales was published in February 1997 this hill was listed as a Twin Marilyn along with Brandy Hill (SN 213 133) as each had a 205m summit height adjoined to a triangulation pillar on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps.  The Twin status was removed from Middleton Hill in August 2013 based on the flush bracket height given to each trig pillar; 206.047m for Brandy Hill and 205.258m for Middleton Hill.  Both hills were subsequently surveyed on the 1st August 2018 by Myrddyn Phillips using a Trimble GeoXH 6000.  The trig pillar for Brandy Hill is positioned on top of a raised earthen embankment of relatively recent construction, whilst the trig pillar for Middleton Hill is positioned on top of a raised earthen embankment that forms a part of an ancient hill fort.  The set-up position for the Trimble was the high point of the adjoining field for Brandy Hill and the high point of the ancient embankment for Middleton Hill; remarkably the Trimble gave each position equal in height; 205.077m.  However, Brandy Hill remains the listed Marilyn and Middleton Hill as the deleted Twin Marilyn as the list author; Alan Dawson considers man-made structures such as the raised earthen embankment on top of Brandy Hill to be natural looking.  Welsh Marilyn total confirmed as 158 and Welsh Submarilyn total confirmed as 24.






Mynydd Anelog    191.4m at SH 15193 27218 

The Leica GS15 gathering data at the summit of Mynydd Anelog (SH 151 272)

This hill was listed as a Submarilyn with an estimated c 149m of drop in the TACit Tables booklet based on the 192m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated bwlch height of c 43m.  The hill was petitioned for promotion to Marilyn status by Myrddyn Phillips who posted the details of his map study including the 41m Vector map bwlch spot height on the RHB Yahoo Groups forum on the 19th March 2012.  The hill was subsequently surveyed by John Barnard, Graham Jackson and Myrddyn Phillips using a Leica GS15 on the 12th July 2013, with Enid Parr, Jeff Parr and Chris Watson also in attendance, resulting in a 191.4m summit height and a 40.4m bwlch height, with these values giving this hill 151.0m of drop.  This hill’s reclassification was accepted by the list author and augmented in to the Marilyn list in July 2013, with a retrospective Hill Reclassification post published on Mapping Mountains.  Welsh Marilyn total increases by one and confirmed as 158 and Welsh Submarilyn total decreases by one and confirmed as 24.
   





Mynydd y Cwm    304.9m at SJ 07307 76734 

Gathering data during the second summit survey of Mynydd y Cwm (SJ 073 767)

Prior to this hill’s GNSS survey it was listed as a Submarilyn with 149m of drop based on the uppermost 305m summit ring contour and the 156m bwlch spot height that appear on the Ordnance Survey 1:25,000 Explorer map.  The hill was petitioned for promotion to Marilyn status by Mark Trengove who assessed the summit in relation to its small uppermost 305m contour on 15th July 2001 and posted his finding on the RHB Yahoo Groups forum.  The hill was subsequently surveyed by John Barnard, Graham Jackson and Myrddyn Phillips over two days; 2nd December 2008 and 15th January 2009 using a Leica 530, resulting in a 304.9m summit height and a 154.9m bwlch height, with these values giving this hill 150.0m of drop.  This hill’s reclassification was accepted by the list author and augmented in to the Marilyn list in April 2009, with a retrospective Hill Reclassification post published on Mapping Mountains.  Welsh Marilyn total increases by one and confirmed as 157 and Welsh Submarilyn total decreases by one and confirmed as 25.
    





Moelfre    335m at SN 32618 36123 

LIDAR bwlch image for Moelfre (SN 326 361)

This hill was originally listed in the TACit Tables booklet as a Submarilyn with 143m of drop based on the 335m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and a bwlch height of 192m.  By July 1997 Alan Dawson had deleted this hill from Submarilyn status as the bwlch position that gave this hill a listed drop value of 143m was incorrect, with LIDAR analysis giving the critical bwlch as 230.8m in height and positioned at SN 41889 33711, and when coupled with this hill’s 335m map summit height these values give this hill 104m of drop.  Welsh Marilyn total confirmed as 156 and Welsh Submarilyn total decreases by one and confirmed as 26.
 




1997 (February) – TACit Tables publishes The Hewitts and Marilyns of Wales. 

Welsh Marilyn total confirmed as 156 and Welsh Submarilyn total confirmed as 27.









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