Mapping Mountains – Hill Reclassifications – 100m Twmpau

Ffridd Uchaf (SH 799 668) – 100m Sub-Twmpau addition

There has been confirmation of an addition to the list of 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Ffridd Uchaf (SH 799 668)

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

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 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.  The list is authored by Myrddyn Phillips, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

100m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Ffridd Uchaf, and this was derived from the Tithe map, and it is adjoined to the Mynydd Hiraethog group of hills, which are situated in the northern part of North Wales (Region A, Sub-Region A1), and it is positioned encircled by minor roads with the A470 road farther to its west, and has the town of Llanrwst 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 not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with 27m of drop, based on the 182m summit spot height and the 155m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

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

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.

Therefore, the confirmation of the addition of this hill to 100m Sub-Twmpau status is due to LIDAR analysis, resulting in a 182.4m summit height and a 155.8m bwlch height, with these values giving this hill 26.6m of drop, which is sufficient for it to be classified as a 100m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Mynydd Hiraethog 

Name:  Ffridd Uchaf 

OS 1:50,000 map:  115

Summit Height:  182.4m (LIDAR) 

Summit Grid Reference:  SH 79916 66826 & SH 79918 66824 (LIDAR) 

Bwlch Height:  155.8m (LIDAR) 

Bwlch Grid Reference:  SH 79340 66846 (LIDAR) 

Drop:  26.6m (LIDAR) 

 

Myrddyn Phillips (August 2026) 

Mapping Mountains – Significant Height Revisions – The Fours – The 400m Hills of England

 

Sourton Tors (SX 543 898) 

There has been a Significant Height Revision to a hill that is listed in the The Fours – The 400m Hills of England, with the summit height, col height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Sourton Tors (SX 543 898)

The criteria for the list that this height revision applies to are:

The Fours – The 400m Hills of England - English hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list is a sub list entitled the Sub-Fours, the criteria for which are all English hills at or above 400m and below 500m in height that have 15m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is available to download in Google Doc format from the Mapping Mountains site.

The Fours - The 400m Hills of England by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Sourton Tors, and it is adjoined to the High Willhays group of hills, which are situated in the south-west of England, and it is positioned with the A386 road to its west, and has the town of Oakhampton towards the north-east.

When the Introduction to the first group of hills for the updated and revised listing of the The Fours – The 400m Hills of England was published by Mapping Mountains on the 10^th September 2022, it was announced that the accompanying sub lists were being revised with the two 390m categories dispensed with and the criteria and name of the 400m Sub-Fours revised.  The one accompanying sub list is now named the Sub-Fours with its criteria being all English hills 400m and above and below 500m in height that have 15m and more and below 30m of drop.

Prior to this revision this hill was listed with 17m of drop, based on the 440m summit spot height adjoined to a triangulation pillar that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and the 423m col spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

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

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 summit image of Sourton Tors (SX 543 898)

LIDAR analysis gives the summit height of this hill as 442.9m positioned at SX 54331 89827 and when compared to its originally listed height this comes 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, Harvey or other interactive 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 with the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 442.9m and this was derived from LIDAR analysis, this is 2.9m higher than the originally listed 440m summit height that appears adjoined to a triangulation pillar on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

 

The full details for the hill are:

Group:  High Willhays

Name:  Sourton Tors

OS 1:50,000 map:  191

Summit Height (New Height):  442.9m (LIDAR)

Summit Grid Reference:  SX 54331 89827 (LIDAR)

Col Height:  423.9m (LIDAR)

Col Grid Reference:  SX 54641 89624 (LIDAR)

Drop:  18.9m (LIDAR)

 

Myrddyn Phillips and Aled Williams (August 2026)

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

Mynydd Margam (SS 819 888) – Pellennig deletion 

There has been a deletion 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 derived from LIDAR analysis conducted by Aled Williams. 

LIDAR image of Mynydd Margam (SS 819 888)

The criteria for the list that this deletion 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 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 Mynydd Margam, and it is adjoined to the Craig y Llyn group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B3), and it is positioned with the B4282 road to its north, the M4 motorway to its south-west and the A4063 road to its east, and has the town of Maesteg towards the north-east.

When the the Y Pellennig – The Remotest Hills of Wales was fiirst published in November 2011 on Geoff Crowder’s v-g.me website, this hill was listed with 2.500km of remoteness and with c 15m of drop, both of which are the minimum required for Pellennig status.

In April 2015 the list was published by Europeaklist in booklet format and by Haroldstreet and Mapping Mountains, with the list on the v-g.me website also updated.  The 2.500km remoteness and 15m drop were retained, with the latter based on the 344m summit spot height adjoined to a triangulation pillar that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and the 329m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

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

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.

Therefore, the deletion of this hill from Pellennig status is due to LIDAR analysis, resulting in a 344.3m summit height and a 331.8m bwlch height, with these values giving this hill 12.5m of drop, which is insufficient for it to be classified as a Pellennig. 

 

The full details for the hill are: 

Group:  Craig y Llyn

Name:  Mynydd Margam

OS 1:50,000 map:  170

Summit Height:  344.3m (LIDAR)

Summit Grid Reference:  SS 81913 88854 (LIDAR)

Bwlch Height:  331.8m (LIDAR)

Bwlch Grid Reference:  SS 82342 88713 (LIDAR)   

Drop:  12.5m (LIDAR) 

Remoteness:  2.500km (no longer applicable)

 

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

 

Y Pellennig – The Remotest Hills of Wales

 

Aled Williams and Myrddyn Phillips (August 2026) 

Topographical Regions, Sub-Regions and Groups

 

Understanding the English Land-Mass

 

Introduction

From the earliest to the latest, the contents of hill listings have been organised into smaller segments, commonly comprising districts, regions, sections or groups.  Doing so makes it easier to find any individual hill and also breaks up the listing into more manageable units. 

We have opted to use Regions, Sub-Regions and Groups for our split of England.  Each follows topography. 

Topography dictates that a land mass is split via watercourses and low points in the terrain, i.e. a col.  If following the course of a river to its source it will be the height and position of the col at or near the source that will be the point at which the Group, Sub-Region and Region is formed.  The advantage of using a topographic system to organise a land mass into smaller units is that the natural lay of the land is represented, with each listed hill connected topographically to its parent peak.  This is not the case for listings that split up the land based on man-made structures, such as roads, or administrative boundaries, such as parish or county units. 

 

England 

The majority of the land that comprises the country of England is commanded by its highest peak, Scafell Pike, which topographically falls under the parentage of Yr Wyddfa, grandfathered by Beinn Nibheis.  The bulk is therefore sandwiched between the bwlch (col) of Yr Wyddfa (height of c46m positioned at NS 75816 78296, beside the Forth & Clyde Canal in Scotland) and the col of Scafell Pike (height of 66.1m positioned at SJ 63688 33945, in a field on the outskirts of Market Drayton in Shropshire). 

However, national borders do not always align with topographical ones.  For instance, the national border between Scotland and England is located circa 130km south of the bwlch of Yr Wyddfa in some places, giving the majority of the Southern Uplands to Scotland.  Conversely, the national border between Wales and England is located circa 60km west of the col of Scafell Pike in certain spots, giving significant portions of the eastern Welsh land-mass to England. 

There are other topographical axis points in Britain beside the two discussed above.  For the purpose of cataloguing and listing hills, such axis points can be used to divide the whole of Britain into manageable topographical units.  However, as the English land-mass represents just one portion of Great Britain, it is prudent to include the remaining land within Scotland and Wales to properly evaluate the essential characteristics of Regions, Sub-Regions and Groups, by doing so an adequate level of consistency and robustness is achieved. 

 

Topographical Regions, Sub-Regions and Groups 

Our topographical split of England comprises four Regions belonging to Scafell Pike, labelled B1-B4.  Region B1 is predominantly in Scotland, Region B2 represents what is roughly referred to as The North, Region B3 the primary portions of what are called The Midlands and The South, and Region B4 what is largely known as The West Country, inclusive of Cornwall, the homeland of the Cornish people. 

These four Regions are ordered into Sub-Regions, again following the rules of topography, which comprise of topographical Groups parented by a significant peak.  This topographical system is mirrored by Scottish Regions (A1-4) and the Welsh Regions (C1-2), which are similarly divided into various Sub-Regions and a multitude of Groups. 

Our topographical system was devised through an initial evaluation at the Group level.  We worked on the principle that Groups should complement one another in terms of both the topographical significance and the absolute quantity of hills contained within the Group boundaries. 

We used the following as rough guidelines:

• Groups should be defined by the topographical limits of parent peaks (i.e. limited by the parent peak col and the surrounding watercourses), aiming to hold no more than circa 100 P30 hills (i.e. prominence of 30m).  A parent peak is considered significant in terms of height and prominence within the context of its Sub-Region or Region.
• Regions should be defined by major topographical axis points, typically holding circa 1000-2500 P30 hills.
• Sub-Regions should be considered for topographical areas containing circa 250-850 P30 hills (i.e. a buffered middle-ground) in order to provide an ordered structure to Regions.
• Regions, Sub-Regions and Groups are defined by natural topography, irrespective of man-made changes.

We have chosen to use the name of the highest peak in each Group as that for the Group name.  Further research and evaluation may mean that some names are amended in the future. 

In summary, we have created manageable Groups of hills based on Regions and Sub-Regions dictated by watercourses and topographical axis points.  The land-mass commanded by Scafell Pike is divided into 103 Groups, but when England’s national borders are applied, 29 Groups in Region B1 are lost to Scotland, which although somewhat countered by gains belonging to the Welsh land-mass, with 2 Groups fully acquired and 11 others partially acquired, still reduces the total to 87 Groups.  The end result is a use of natural occurring features to define units of land that are manageable for hill-listing purposes. 

 

Aled Williams and Myrddyn Phillips (August 2026) 

 

Sub-Region B1A Groups:
1.       Hendry's Corse [Scotland]
2.      Scald Law [Scotland]
3.      Pyked Stane Hill [Scotland]
4.      Windlestraw Law [Scotland]
5.      Meikle Says Law [Scotland]
6.      Spartleton [Scotland]  

Sub-Region B1B Groups:
7.      Hill of Stake [Scotland]
8.     Nutberry Hill [Scotland]
9.      Tinto [Scotland]
10.  Green Lowther [Scotland]
11.   Queensberry [Partial]
12.  Culter Fell [Scotland]
13.  White Coomb [Scotland]
14.  Broad Law [Scotland]
15.   Andrewhinney Hill [Scotland]
16.  Ettrick Pen [Scotland]
17.   Wisp Hill  [Scotland]

Sub-Region B1C Groups:
18.  Cairnsmore of Carsphairn [Scotland]
19.  Colt Hill [Scotland]
20. Wether Hill [Scotland]
21.  Bogrie Hill [Scotland]
22. Criffel [Scotland]
23. Corserine [Scotland]
24. Merrick [Scotland]
25.  Craiglee [Scotland]
26. Lamachan Hill [Scotland]
27.  Cairnsmore of Fleet [Scotland]
28. Beneraird [Scotland]
29. Cairn Pat [Scotland]

Sub-Region B1D Groups:
30. Cushat Law
31.  The Cheviot [Partial]
32. Windy Gyle [Partial]
33. Tosson Hill
34. Peel Fell [Partial]
35.  Cauldcleuch Head [Scotland]
36. Sighty Crag [Partial]

Sub-Region B2A Groups:
37.  Skiddaw
38. Grasmoor
39. High Stile
40. Great Gable
41.  Scafell Pike
42. Black Combe
43. The Old Man of Coniston
44. High Raise
45.  Helvellyn
46. High Street
47.  Tarn Crag
48. Grayrigg Forest

Sub-Region B2B Groups:
49. Cross Fell
50. Burnhope Seat
51.   Chapel Fell Top
52.  Great Shunner Fell
53.  Wild Boar Fell
54.  Whernside
55.  Ingleborough
56.  Pen y Ghent
57.  Urra Moor
58. Bishop Wilton Wold

Sub-Region B3A Groups:
59.  Pendle
60. Lad Law
61.  Cowpe Moss
62. Black Hill
63. Kinder Scout
64. High Neb
65.  Axe Edge
66. Shining Tor
67.  The Roaches

Sub-Region B3B Groups:
68. The Wolds
69. Whatborough Hill
70. Arbury Hill
71.   Bardon Hill
72.  The Wrekin
73.  The Cleeve
74.  Haddington Hill
75.  Therfield
76.  Beacon Hill

Sub-Region B3C Groups:
77.  Beacon Batch
78. Long Knoll
79.  Milk Hill
80.Walbury Hill
81.  Oakshott Hanger
82. St. Boniface Down
83. Butser Hill
84. Black Down
85. Leith Hill
86. Botley Hill
87. Detling Hill

Sub-Region B4A Groups:
88.Dunkery Beacon
89. Stoodleigh Beacon
90. Lype Hill
91.  Staple Hill
92. Lewesdon Hill
93. Eggardon Hill

Sub-Region B4B Groups:
94. Great Links Tor
95. High Willhays
96. Cosdon Hill
97. Broad Barrow
98. Ryder's Hill
99. Bronn Wenneli
100. Kilmar Tor
101. Hen's Barrow
102. Karn Menelys
103. Karnan Bygh

Sub-Region C1A Groups:
14.  Moel y Gamelin [Partial]

Sub-Region C1B Groups:
15.   Raw Head [Partial]
16.  Craig Berwyn [Partial]
17.   Foel Cedig [Partial]

Sub-Region C2A Groups:
35.  Mynydd Du [Partial]

Sub-Region C2B Groups:
38. Cilfaisty [Partial]
39. Bigwn [Partial]
40. Fforest Glud [Partial]
41.  Gwaun Ceste [Partial]
42. Stiperstones [Partial]
43. Brown Clee
44. Worcestershire Beacon
45.  May Hill [Partial]