Monday, 26 June 2017

Mapping Mountains – Hill Reclassifications – 200m Twmpau


200m Twmpau – Hill Reclassifications

The 200m Twmpau (thirty welsh metre prominences and upward) are the Welsh hills at or above 200m and below 30om in height that have a minimum drop of 30m.  Accompanying the main P30 list is a sub list entitled the 200m Sub-Twmpau with the qualification to this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop.

The list is authored by Myrddyn Phillips and the posts that have appeared on Mapping Mountains detailing the additions, reclassifications and deletions to the main P30 list and the sub list appear below presented chronologically in receding order.









Mapping Mountains - Hill Reclassifications - 200m Twmpau

Erw Penlan (SO 045 495) – 200m Sub-Twmpau addition (10th reclassification)

Survey post for Erw Penlan

Significant Name Changes post for Erw Penlan


There has been a confirmation of an addition to the 200m Twmpau (thirty welsh metre prominences and upward) ranks of hills due to a survey with the Trimble GeoXH 6000, with the survey that confirmed this addition being conducted on the 13th June 2017.

The criteria for 200m Twmpau status is all Welsh hills at or above 200m and below 300m in height with 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop, and it is the inclusion of this hill in the 200m Sub-Twmpau that has been confirmed. 

The hill did not appear in the original Welsh P30 lists on Geoff Crowder’s v-g.me website as it did not meet the criteria then adopted for the Hills to be surveyed sub list.  The hill was later classified and listed in the sub category after this was standardised and interpolated drop values added, and was included when the updates to the 200m Welsh P30s were published for the Mynydd Epynt group of hills on Mapping Mountains on the 25th August 2014.  The listing this hill is now a part of is named Twmpau (thirty welsh metre prominences and upward) and its height, drop and status was confirmed by a survey with the Trimble GeoXH 6000.   

Prior to the survey with the Trimble GeoXH 6000 the hill was listed by the name of Coetgae Fawr with an estimated c 21m of drop, based on the 213m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 192m based on interpolation of bwlch contouring between 190m – 200m.

The name that this hill is being listed by is Erw Penlan (see Significant Name Changes) and it is adjoined to the Mynydd Epynt range, which is situated in the south-eastern part of Mid and West Wales (Region B, Sub-Region B2) with its Cardinal Hill being Clepyn Melyn (SN 961 464), and it is positioned above the A 483 road which is to the hill’s north and east, with the town of Llanfair-ym-Muallt (Builth Wells) positioned to its north.

As the hill does not form a part of designated open access land permission to visit should be sought, for those wishing to do so a public footpath connects between minor country lanes to the north and south of the hill’s summit and proceeds around the upper western part of the hill.


The full details for the hill are:


Cardinal Hill:  Clepyn Melyn

Summit Height:  212.1m (converted to OSGM15)

Name:  Erw Penlan

OS 1:50,000 map:  147

Summit Grid Reference:  SO 04597 49535  

Drop:  20.9m (converted to OSGM15)


Erw Penlan (SO 045 495) now confirmed as a 200m Sub-Twmpau addition


Myrddyn Phillips (August 2017)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Y Pincin (SH 723 581) – 200m Twmpau addition (9th reclassification)

Survey post for Y Pincin


There has been a confirmation of an addition to the 200m Twmpau (thirty welsh metre prominences and upward) ranks of hills due to a survey with the Trimble GeoXH 6000, with these details being retrospective as the survey that confirmed this addition was conducted on the 24th December 2013.

The criteria for 200m Twmpau status is all Welsh hills at or above 200m and below 300m in height with 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop. 

This hill did not appear in the original Welsh P30 lists when published on Geoff Crowder’s v-g.me website even though the hill is given a 264m summit spot height on the Ordnance Survey 1:25,000 Explorer map and has bwlch contouring between 220m – 230m.  Its addition to the P30 ranks was announced shortly before the hill was surveyed with the Trimble GeoXH 6000, and prior to this survey the hill was listed with c 36m of drop.

The name of the hill is Y Pincin and it is situated in the Carneddau range with its Cardinal Hill being Creigiau Gleision (SH 729 615) and is positioned immediately above the A5 road which is to its south and the small community of Capel Curig.

The upper section of the hill is a part of designated open access land, with a public footpath leaving Capel Curig to the west of the hill and heading toward the summit.  Although this hill makes an enjoyable walk and scramble in its own right, a more fulfilling experience can be had when combining it with its higher neighbours toward the north.


The full details for the hill are:

Cardinal Hill:  Creigiau Gleision

Summit Height:  263.5m (converted to OSGM15)

Name:  Y Pincin

OS 1:50,000 map:  115

Summit Grid Reference:  SH 72357 58126

Drop:  34.7m (converted to OSGM15)


Y Pincin (SH 723 581) has now been confirmed as a 200m Twmpau by a survey with the Trimble GeoXH 6000



Myrddyn Phillips (August 2017)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Dinas Mawr (SH 808 539) – 200m Sub-Twmpau reclassified to 200m Twmpau (8th reclassification)

Survey post for Dinas Mawr


There has been a confirmation of a reclassification to the 200m Twmpau (thirty welsh metre prominences and upward) ranks of hills due to a survey with the Trimble GeoXH 6000, with these details being retrospective as the survey that confirmed this reclassification was conducted on the 24th December 2013.

The criteria for 200m Twmpau status is all Welsh hills at or above 200m and below 300m in height with 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop. 

This hill was listed in the Hills to be surveyed sub list accompanying the original Welsh P30 lists on Geoff Crowder’s v-g.me website and was only reclassified to P30 status when the sub list was standardised and interpolated drop values were accepted for qualification to the main P30 list.

Prior to the survey with the Trimble GeoXH 6000 the hill was listed with 33m of drop based on the 254m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 221m bwlch spot height that appears on the Ordnance Survey enlarged mapping hosted on the Geograph website.

The name of the hill is Dinas Mawr and it  is situated in the Mynydd Hiraethog range with its Cardinal Hill being Mwdwl Eithin (SH 917 540) and is positioned immediately above the A5 road which is to its south, and is placed between the small communities of Capel Garmon to the north north-east and Penmachno to the south south-west.

The upper section of the hill is a part of designated open access land and this can be accessed from public footpaths originating from the A5 road south-west of the summit or from a minor lane to the east of the summit.


The full details for the hill are:

Cardinal Hill:  Mwdwl Eithin

Summit Height:  254.0m (converted to OSGM15)

Name:  Dinas Mawr

OS 1:50,000 map:  116

Summit Grid Reference:  SH 80884 53931

Drop:  33.9m (converted to OSGM15)


Dinas Mawr (SH 808 539) this hill's reclassification to 200m Twmpau status is now confirmed by a survey with the Trimble GeoXH 6000


Myrddyn Phillips (August 2017)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Pen y Gaer (SO 139 976) – 200m Twmpau reclassified to Trichant (7th reclassification)

Survey post for Pen y Gaer


There has been a reclassification of a 200m Twmpau (thirty welsh metre prominences and upward) to the listing of Y Trichant due to surveying with the Trimble GeoXH 6000.

The details relating to this hill’s inclusion in the listing of Y Trichant are retrospective as the survey with the Trimble took place on the 11th January 2015 and the Hill Reclassifications post for its 300m Twmpau status was published on Mapping Mountains on the 12th January 2015.

The criteria for 200m Twmpau status is all Welsh hills at or above 200m and below 300m in height with 30m minimum drop, whilst Y Trichant is the title for the hills in the 300m height band of the Twmpau and takes in all Welsh hills at or above 300m and below 400m in height with 30m minimum drop, with the introduction to the re-naming of this list appearing on Mapping Mountains on the 13th May 2017.

Prior to the survey with the Trimble GeoXH 6000 the hill was listed with 87m of drop based on the 299m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and the 212m bwlch spot height that appears on the Ordnance Survey enlarged mapping hosted on the Geograph website.

The hill is situated in the Carnedd Wen range with its Cardinal Hill being Stingwern Hill (SJ 132 014and is placed in the North Wales Region (Region A, Sub-Region A4), and is positioned with the small community of Bettws Cedewain to the west south-west and Aber-miwl (Abermule) to the south-east.

As the summit of the hill is not a part of designated open access land permission to visit its high point should be sought.  For those seeking this and wishing to visit there is a public footpath just to the north of the summit which can be accessed from either the north-east or the south-west.

The name of the hill is Pen y Gaer and it is only the third hill that I know of whose status has been altered due to the Ordnance Survey remodelling known as OSGM15.  This remodelling has increased the accurately known height of hills in Wales by approximately 2-4cm, and the other two hills whose status was altered because of OSGM15 are Calf Top (SD 664 856) and Carn Ysgubor (SM 699 246).


Surveyed height of Pen y Gaer pre OSGM15 = 299.974m

Surveyed height of Pen y Gaer post OSGM15 = 300.002m



The full details for the hill are:

Cardinal Hill:  Stingwern Hill

Summit Height:  300.0m (converted to OSGM15)

Name:  Pen y Gaer

OS 1:50,000 map:  136

Summit Grid Reference:  SO 13997 97677

Drop:  88m



Pen y Gaer (SO 139 976) reclassified from a 200m Twmpau to a Trichant



Myrddyn Phillips (June 2017)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Moelfryn (SH 569 511) – 200m Twmpau reclassified to 200m Sub-Twmpau (6th reclassification)


There has been a reclassification to the listing of Twmpau (thirty welsh metre prominences and upward) hills due to analysis of LIDAR data by Aled Williams.  The hill was listed in the 200m height band of P30 Twmpau hills and it has now been reclassified to a 200m Sub-Twmpau, with the criteria for 200m Twmpau status being all Welsh hills at or above 200m and below 300m in height with 30m minimum drop, and the 200m Sub-Twmpau being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop.

The hill was originally listed in the sub list that accompanied the P30 lists when published on Geoff Crowder’s v-g.me website under the title of ‘Hills to be surveyed.’  When this list was re-evaluated the hill was reclassified to a P30 with c 30m of drop based on its 277m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps and an estimated bwlch height of c 247m.  However, the 277m spot height may be erroneous as this summit is immersed in conifer plantation and the only spot height preceding it that has appeared on Ordnance Survey maps is the imperial height of 901ft (274.6m) which originated on the Six-Inch series.  Therefore there seems no evidence to support how a spot height has changed by 2.4m when the summit is unsighted and blanketed in trees.

The hill is situated in the north-eastern part of the Beddgelert Forest and is adjoined to Crib Nantlle and the Moel Hebog group of hills, with its Cardinal Hill being Pt. 734m (SH 525 502) and is placed in the Region of North Wales (Region A, Sub-Region A1), and is situated between the small communities of Rhyd-ddu to its north and Beddgelert to its south south-east.

As the hill is immersed in conifer plantation any ascent may prove problematical, but forest tracks are marked on the map to the north-east and south-west of the summit, with the former indicated as giving nearer access.

The name of the hill is Moelfryn and its reclassification to a 200m Sub-Twmpau is due to the analysis of 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:


Moelfryn

Summit Height:  269.0m

Summit Grid Reference:  SH 56900 51151

Bwlch Height:  246.1m

Bwlch Grid Reference:  SH 56416 51301

Drop:  22.9m


Therefore, the 269.0m LIDAR data produced for the summit position at SH 56900 51151 and the 246.1m LIDAR data produced for the bwlch position at SH 56416 51301 gives this hill 22.9m of drop.  However as the DTM model may have struggled to model the summit hillock the detail from the Ordnance Survey Six-Inch map is being taken for the summit.


The full details for the hill are:


Cardinal Hill:  Pt. 734m (SH 525 502)

Summit Height:  275m (height rounded up from Six-Inch map)

Name:  Moelfryn

OS 1:50,000 map:  115

Summit Grid Reference:  SH 56900 51151  

Drop:  29m (summit height from Six-Inch map and bwlch height from LIDAR data)



My thanks to Aled Williams for sending the details of this hill to me.

Myrddyn Phillips (May 2017)







Mapping Mountains - Hill Reclassifications - 200m Twmpau


Mynydd y Drum (SN 807 097) - 200m Twmpau reclassified to 200m Sub-Twmpau (5th reclassification)

Survey post for Mynydd y Drum


There has been a reclassification to the listing of Twmpau (thirty welsh metre prominences and upward) hills due to analysis of LIDAR data by Kevin McGovern and also independently by Aled Williams, and subsequently confirmed via a survey with the Trimble GeoXH 6000.  The hill has been reclassified from a 200m Twmpau to a 200m Sub-Twmpau, with the criteria for the former being all hills in Wales at or above 200m and below 300m in height that have a minimum drop of 30m, and the criteria for the sub category being all hills in Wales at or above 200m and below 300m in height with 20m or more and below 30m of drop.

The hill had been listed with an estimated drop of c 53m based on an estimated bwlch height of c 244m and the 297m summit height positioned at SN 807 098 derived from the spot height that appears on the Ordnance Survey 1:25,000 Explorer map numbers 12 and 165, whilst the Ordnance Survey 1:50,000 Landranger map number 160 gives a 298m summit spot height at the same position.  This latter spot height is derived from the 978.1ft (298.1ft) height on the Ordnance Survey old Six-Inch map.

When this hill was originally listed in the Welsh P30 lists on the v-g.me website it had an accompanying note which stated ‘3 points of 300m on 1985 map may probably no longer exist (quarrying)’.  The hand written Master List stated ‘Due to opencast workings the three points of 300c at GR 830 112 on 1985 1:50,000 map probably no longer exist’.  These three points are in the vicinity of where a 984ft (299.9m) height appears on the Ordnance Survey old Six Inch map and in all likelihood signified where the summit of this hill was once positioned.  Since this time the opencast workings which take in the northern and eastern part of the larger hill known as Mynydd y Drum have destroyed the old 984ft (299.9m) summit, but in its place are two separate hills comprising the spoil from the mine workings, with this Hill Reclassifications post concentrating on the remaining ‘natural’ and now lower of these three summits. 

Prior to analysis of LIDAR data Mynydd y Drum was listed with one summit, but due to opencast mining a further two summits have been created which are artificial and comprise the remains of waste spoil, the hill which this Hill Reclassifications post details is the remaining ‘natural’ summit, which is now lower in height compared to the two artificial summits, this has resulted in new bylchau heights and positions and also drop values for these three hills, all of these will be detailed in this and the two previous Hill Reclassifications posts, with the other two hills being Teisen Priodas (SN 820 108) and MRF Tip (SN 828 114).

The hill is adjoined to the Fforest Fawr group with its Cardinal Hill being Fan Gyhirych (SN 880 191) and is placed in the Region of South Wales (Region C, Sub-Region C2), and is positioned between the small town of Ystradgynlais to the north-west and the village of Blaendulais (Seven Sisters) to the south-east.

The upper part of the hill is situated within open access land and can be easily accessed from a number of public footpaths that emanate from Cwm Tawe (Swansea Valley) to the north-west and from Cwm Dulais (Dulais valley) from the south-east.

The name of the hill is Mynydd y Drum and its reclassification to a 200m Sub-Twmpau is due to the analysis of LIDAR data by Kevin McGovern and also independently by Aled Williams.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

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


Mynydd y Drum

Summit Height:  296.1m (converted to OSGM15)

Summit Grid Reference:  SN 80720 09754

Bwlch Height:  271.8m (converted to OSGM15)

Bwlch Grid Reference:  SN 81526 10520

Drop:  24.3m


Therefore, the 296.1m LIDAR data produced for the summit position at SN 80720 09754 and the 271.8m LIDAR data produced for the bwlch position at SN 81526 10520 is sufficient for this hill to be reclassified from a 200m Twmpau to a 200m Sub-Twmpau with 24.3m of drop, with the details from the Trimble GeoXH 6000 survey being 296.2m (converted to OSGM15) summit at SN 80718 09753 and 271.4m bwlch (converted to OSGM15) at SN 81526 10519), giving this hill 24.8m of drop.

This now revises the total in the 200m Twmpau and the list will be updated accordingly.


The full details for the hill are:

Cardinal Hill:  Fan Gyhirych

Summit Height:  296.2m (converted to OSGM15, Trimble data)

Name:  Mynydd y Drum

OS 1:50,000 map:  160

Summit Grid Reference:  SN 80718 09753 
  
Drop:  24.8m (converted to OSGM15, Trimble data)


Mynydd y Drum (SN 807 097) now reclassified to a 200m Sub-Twmpau

My thanks to Mark Jackson for bringing the details of this hill to my attention, and to Kevin McGovern and Aled Williams for their analysis of LIDAR data.


Myrddyn Phillips (March 2017)







Mapping Mountains - Hill Reclassifications - 200m Twmpau

Y Ceiliog Mawr (SH 594 598) - 200m Twmpau addition (4th reclassification)


There has been a new addition to the 200m Twmpau (thirty welsh metre prominences and upward) hill list instigated through analysis of LIDAR data by Aled Williams.  The hill is one that Aled first proposed as a prospective P30 Twmpau approximately two years ago and it then waited to be Trimbled, but as it looked a daunting prospect the Trimble surveyor shied away from his duties, and in the meantime as LIDAR data is proving highly accurate I am using the data that Aled has obtained.

The hill is situated in the Glyderau group of hills with its Cardinal Hill being Y Garn (SH 630 595) and is placed in the Region of North Wales (Region A, Sub-Region A1).  The hill is positioned above Llyn Peris which is to its south and the small community of Nant Peris to its south-east and the town of Llanberis to its west.  The hill is a part of the old Dinorwig Slate Quarries, and can be accessed from tracks leading into the hill from the south-east and from the west.

The hill is known locally as Y Ceiliog Mawr which translates into English as the big cockerel.  I am thankful to Eric Jones for the information relating to this name and the history of the hill which comes from the following two passages on the Geograph website:


The Ceiliog Mawr is an igneous intrusion within the Dinorwig Quarries.  Several attempts were made to remove the intrusion but a considerable section of it remains.  "Ceiliog Mawr" means big cockerel.

Buildings associated with the Dinorwig HEP station have been built around the foot of a slightly modified 'cockerel'.  Three attempts were made in the past to 'slaughter the cockerel'.  In 1896 Mr Brinckman, the general manager, decided that the days of the cockerel were numbered.  On the day, the quarrymen were invited to witness what "a real explosion was like".  The cream of the Welsh aristocracy, and dozens of cameramen, were also invited to watch the demise of the cockerel.  The fateful moment came and the button pressed on the battery firer (the only occasion in the history of the quarry for a battery firer to be used).  A huge pall of smoke emerged from the rock.  When it cleared, Y Ceiliog Mawr stood unscathed.  A visit by the Prince and Princess of Wales in May 1902 was an excuse for another go, this time using two tons of explosive, only to leave more egg on the managers' face.  Finally, in 1905, 10 shafts were dug into the outcrop at a cost of £437-12-2 and explosives set at the bottom of each.  Again, only a few loose rocks were dislodged.  Ever since, the Ceiliog Mawr has been an icon of Dinorwig Quarry.


Current Ordnance Survey 1:50,000 and 1:25,000 mapping does not give this hill any ring contours, as is the norm for areas of land that have been quarried.  The hill is of interest (and quite daunting) as it is only now listed as a 200m Twmpau through the quarrying activities of past years, as it has been left as a stone monolith separated from its connecting bwlch by over 37m of vertical height.


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


Y Ceiliog Mawr

Summit Height:  220.3m

Summit Grid Reference:  SH 59467 59848

Bwlch Height:  182.8m

Bwlch Grid Reference:  SH 59538 59823

Drop:  37.5m


Therefore, the 220.3m LIDAR data produced for the summit position at SH 59467 59848, and the 182.8m LIDAR data produced for the bwlch position at SH 59538 59823 is sufficient for this hill to be included in the list of 200m Twmpau hills with 37.5m of drop, and therefore Y Ceiliog Mawr is included in the listing of Twmpau which will be updated accordingly.


The full details for the hill are:


Cardinal Hill:  Y Garn

Summit Height:  220.3m (LIDAR data)

Name:  Y Ceiliog Mawr

OS 1:50,000 map:  115

Summit Grid Reference:  SH 59467 59848

Drop:  37.5m (LIDAR data)



My thanks to Aled for supplying the details of his LIDAR analysis of this hill.

Y Ceiliog Mawr - the new 200m Twmpau.  Photo © Aled Williams

To view an old and a relatively recent photograph of Y Ceiliog Mawr {here} {here}


Myrddyn Phillips (December 2016)






Mapping Mountains - Hill Reclassifications - 200m Twmpau

Gallt y Celyn (SH 811 542) - 200m Sub-Twmpau reclassified to 200m Twmpau (3rd reclassification)

Summit survey post for Gallt y Celyn

Bwlch survey post for Gallt y Celyn

Significant Name Changes post for Gallt y Celyn


There has been a reclassification within the 200m Twmpau (thirty welsh metre prominences and upward) hill list instigated by a survey with the Trimble GeoXH 6000.   The hill has a convoluted history of reclassification and is situated just to the north of the A 5 and southward of the small community of Capel Garmon and south-eastward of the town of Betws-y-coed, and is positioned in the Mynydd Hiraethog range of hills.

The Trimble GeoXH 6000 survey that resulted in this hill’s reclassification from a 200m Sub-Twmpau to a 200m Twmpau was conducted in the afternoon of the 23th February 2016 on a beautiful winter’s day in good, dry and sunny conditions.

The hill is unnamed on current Ordnance Survey maps but is given as a part of Gallt y Celyn on the Tithe map and therefore this name is deemed appropriate to use.
Access to the hill is relatively easy as there is a public footpath approaching from the north which can be accessed from Capel Garmon, and also one from the south-east which can be accessed from a steep minor lane that heads north from the A 5.  The summit of the hill is only a short distance from where these footpaths meet and is on open access land.

The hill has a convoluted history of inclusion and exclusion from the 200m P30 Welsh list as it was originally included in the ‘Hills to Survey’ Sub-List that accompanied the main P30 lists on Geoff Crowder’s v-g.me website.  This Sub-List was reliant upon the details on Ordnance Survey maps being correct and did not take in contour interpolation for inclusion within the main P30 list.  After the Sub-List was standardised and contour interpolation used, the hill was reclassified to a P30 with c 30m of drop, based on a 258m summit spot height and an estimated bwlch height of c 238m.  To complicate matters this hill had twin tops, both given a 258m spot height on Ordnance Survey maps, these tops were surveyed with the Trimble on the 24th December 2013 with the following results:


257.610m (converted to OSGM15) at SH 81121 54259.

257.093m (converted to OSGM15) at SH 81007 54476.


Although the twin tops had been separated the bwlch was not surveyed and as it was estimated to be c 238m high, the drop for this hill was accepted as being just under the qualifying minimum drop of 30m and therefore the hill re-joined the ranks of Subs.

It was always my intention to survey the bwlch and determine once and for all the classification of the hill, and on the 23rd February I found myself immersed in a water laden bog gathering the allotted five minutes of data.  This survey resulted in a bwlch height of 227.5m (227.529m, converted to OSGM15), which gave this hill 30.1m (30.081m) of drop, and therefore it re-joins the ranks of P30 Twmpau hills.


The full details for the hill are:

Cardinal Hill:  Mwdwl Eithin

Summit Height:  257.6m (converted to OSGM15)

Name:  Gallt y Celyn

OS 1:50,000 map:  116

Summit Grid Reference:  SH 811 542

Drop:  30.1m (converted to OSGM15)


Gallt y Celyn (SH 811 542) in the centre foreground of this photograph and which has now been re-instated as a 200m P30 Twmpau.  Photograph taken from the summit of Dinas Mawr (SH 808 539)

For details on the survey that resulted in this hill being reclassified from a 200m Sub-Twmpau to a 200m Twmpau please click {here} for summit and {here} for the bwlch survey.

Myrddyn Phillips (February 2016)







Mapping Mountains - Hill Reclassifications - 200m Twmpau

Bwlch Clump (SJ 170 108) - 200m Twmpau reclassified to 200m Sub-Twmpau (2nd reclassification)

Survey post for Bwlch Clump

Summit Relocations post for Bwlch Clump

Significant Name Changes post for Bwlch Clump


There has been a reclassification within the 200m Twmpau (thirty welsh metre prominences and upward) hill list instigated by a survey with the Trimble GeoXH 6000.   The hill has twin map heighted summits and is situated to the south-east of Dyffryn Meifod and to the north-west of the Maesmawr valley and forms part of the Carnedd Wen range of hills.

These details are retrospective, as the Trimble GeoXH 6000 survey that resulted in this hill’s reclassification from a P30 Twmpau hill to a 200m Sub- Twmpau hill was conducted in the afternoon of the 20th January 2016 on a beautiful crisp winter day in good, dry and sunny conditions.

The lower section of the hill can be accessed from public footpaths to its west and east.  However, its summit does not appear on open access ground, therefore permission to visit the high point should be sought.

The hill was originally included in the main 200m P30 list that appeared on Geoff Crowder’s v-g.me website as a single summit under the current 1:25,000 Explorer map height of 262m (SJ 173 109), and listed under the partly invented name of Pen y Bryn Wood (Bryn Wood being the name of the wood to the north-east of the originally listed hill’s summit).  The hill gained a twin summit when the Ordnance Survey enlarged map on the Geograph website included a 262m spot height for the adjacent hill at SJ 170 108, which was named as Bwlch Clump on this map.  According to map contours the drop between each was not sufficient for both to be included as P30s, with interpolation suggesting c 19m of drop.

Therefore the purpose of this survey was to ascertain which of the two summits is higher and separate their twin top status, and see if the drop between each was sufficient for the lower Trimbled summit to be included as a Sub-Twmpau and ascertain if the higher summit retained its P30 status, as the listed drop value for this hill was c 30m, which was based on bwlch contour interpolation.


The survey results for this once twin topped P30 are:


Pt . 262.8m (originally listed as Pen y Bryn Wood)

262.8m (converted to OSGM15) summit at SJ 17354 10914

243.5m (converted to OSGM15) bwlch at SJ 17190 10797

19.4m drop



Bwlch Clump

263.9m (converted to OSGM15) summit at SJ 17063 10813

234.9m (converted to OSGM15) bwlch at SJ 17089 10581

29.1m drop


Therefore the survey with the Trimble GeoXH 6000 confirms that Bwlch Clump is 1.1m higher than Pt. 262.8m, and that Pt. 262.8m has 19.4m of drop and is not listed as a Sub-Twmpau, and that Bwlch Clump has 29.1m of drop and is therefore reclassified to a 200m Sub-Twmpau.


The full details for the new status of this hill are:


Cardinal Hill:  Carnedd Wen

Summit Height:  263.9m (converted to OSGM15)

Name:  Bwlch Clump

OS 1:50,000 map:  125

Summit Grid Reference:  SJ 17063 10813

Drop:  29.1m (converted to OSGM15)


Pt. 262.8m - now reclassified from a twin topped P30 to a non Sub-Twmpau.  How the mighty fall!!!

Bwlch Clump - now reclassified from a twin topped P30 to a 200m Sub-Twmpau

For details on the survey that resulted in this hill being reclassified from a 200m Twmpau to a 200m Sub-Twmpau please click {here}


Myrddyn Phillips (January 2016)







Mapping Mountains - Hill Reclassifications - 200m Twmpau

Broniarth (SJ 166 120) - 200m Sub-Twmpau addition (1st reclassification)

Survey post for Broniarth


There has been a confirmation of a new addition to the Sub category within the 200m Twmpau (thirty welsh metre prominences and upward) hill list instigated by a survey with the Trimble GeoXH 6000.   The hill is situated between the small community of Meifod to its north-west and that of Maesmawr to its south-east and is part of the Carnedd Wen range of hills.

These details are retrospective, as the Trimble GeoXH 6000 survey that resulted in this hill’s confirmation as a 200m Sub- Twmpau was conducted on the 20th January 2016 on a beautiful crisp winter day in good, dry and sunny conditions.

The hill can be easily accessed from its south where a narrow lane crosses from south-west to north-east across its southerly flank.  This would be a short visit of no more than a few minutes, so combining the hill with some of its neighbours is recommended.  However, permission should be sought for those wishing to visit as the summit is not on open access land.

The hill is unnamed on current Ordnance Survey 1:25,000 Explorer maps but is part of land known locally as Broniarth and which appears on some Ordnance Survey maps as an extended name of either Broniarth or Broniarth Hill.

This is a confirmation of this hill’s addition to the 200m Sub-Twmpau ranks as current Ordnance Survey enlarged mapping on the Geograph website has a 247m spot height on this hill’s bwlch, with the summit having a 268m spot height on the Ordnance Survey 1:25,000 Explorer map and the enlarged map hosted on the Geograph website.  These values give the hill 21m of drop, which compares favourably with the Trimble survey of 21.5m of drop.

The survey with the Trimble GeoXH 6000 resulted in a 267.9m (converted to OSGM15) summit height and a 246.5m (converted to OSGM15) bwlch height, giving this hill 21.5m of drop and confirming its entry in to the 200m Sub-Twmpau ranks.


The full details for the hill are:

Cardinal Hill:  Carnedd Wen

Summit Height:  267.9m (converted to OSGM15)

Name:  Broniarth

OS 1:50,000 map:  125

Summit Grid Reference:  SJ 16648 12055

Drop:  21.5m (converted to OSGM15)


Broniarth (SJ 166 120) 200m Sub-Twmpau status now confirmed by the Trimble GeoXH 6000

For details on the survey that resulted in this hill being confirmed as a 200m Sub-Twmpau please click {here}

Myrddyn Phillips (January 2016)





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