Mapping Mountains – Significant Height Revisions – 200m Twmpau and Y Trechol – The Dominant Hills of Wales

Mynydd Llwyd (ST 433 935)

There has been a Significant Height Revision to a hill that is listed in the 200m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height, their locations, the drop, dominance and status of the hill derived from detail on contemporary and historic Ordnance Survey maps.

The criteria for the two listings this height revision affects are:

200m Twmpau – Welsh hills at or above 200m and below 300m in height that have 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.

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.

The name the hill is listed by is Mynydd Llwyd and it is adjoined to the Gwent Is Coed group of hills which are situated in the south-eastern part of South Wales (Region C, Sub-Region C3), and it is positioned with the A449 road to its west, the A48 road to its south and the B4235 road to its north-east, and has the city of Casnewydd (Newport) towards the west south-west.

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

When the original 200m 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 under the name of Gray Hill and listed with a 273m summit height, based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map, with an accompanying note stating; 275m on 1986 1:50000 map.

Extract from the Ordnance Survey 1:50,000 Landranger map

Since publication of these P30 lists on Geoff Crowder’s v-g.me website there have been a number of Ordnance Survey maps made available online, some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website, and it is this scale of mapping that shows a 901.8ft (274.9m) Surface Height on the summit area of this hill.  It is this height that has been rounded up and appears as the 275m spot height on contemporary Ordnance Survey 1:50,000 Landranger maps.

Extract from the Ordnance Survey series of Six-Inch maps

As the Surface Height is more accurate than the 273m spot height which has been ascertained from photogrammetry, the 275m height is now used for this hill, and 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 summit height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR.  Also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis. 

Therefore, this hill’s new listed summit height is 275m and this was derived from the spot height that appears on the Ordnance Survey 1:50,000 Landranger map, which in itself has been derived from the Surface Height on the Ordnance Surveys series of Six-Inch maps.

The full details for the hill are:

Group:  Gwent Is Coed

Name:  Mynydd Llwyd

OS 1:50,000 map:  171, 172

Summit Height (New Height):  275m (spot height)

Summit Grid Reference:  ST 43399 93559 (hand-held GPS via DoBIH)

Bwlch Height:  c 183m (interpolation)

Bwlch Grid Reference:  ST 42894 93984 (interpolation)

Drop:  c 92m (spot height summit and interpolated bwlch)

Dominance:  33.45% (spot height summit and interpolated bwlch)

Myrddyn Phillips (May 2020)

Mapping Mountains – Significant Name Changes – 200m Twmpau and Y Trechol – The Dominant Hills of Wales

Mynydd Llwyd (ST 433 935)

There has been a Significant Name Change to a hill that is listed in the 200m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height, their locations, the drop, dominance and status of the hill derived from detail on contemporary and historic Ordnance Survey maps.

The criteria for the two listings that this name change applies to are:

200m Twmpau - 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, 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, and which is now available in its entirety on Mapping Mountains in Google Doc format.

The hill is adjoined to the Gwent Is Coed group of hills which are situated in the south-eastern part of South Wales (Region C, Sub-Region C3), and it is positioned with the A449 road to its west, the A48 road to its south and the B4235 road to its north-east, and has the city of Casnewydd (Newport) towards the west south-west.

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

The hill appeared in the original 200m Welsh P30 list on Geoff Crowder’s v-g.me website under the name of Gray Hill, which is a name that appeared near the summit of this hill on Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps of the day.

Gray Hill

273m

ST434935

171/172

14

275m on 1986 1:50000 map

Since publication of these P30 lists on Geoff Crowder’s v-g.me website there have been a number of Ordnance Survey maps made available online, some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website, whilst others are current and digitally updated such as the Vector Map Local that used to be hosted on the Geograph website and which is named the Interactive Coverage Map.  Two of the historic maps now available are the Ordnance Survey Draft Surveyors map which formed the basis for the first publicly available Ordnance Survey One-Inch ‘Old Series’ map, and it is these maps that form the basis for the change in this hill’s listed name.

The Draft Surveyors maps consist of the preliminary drawings made by the Ordnance Surveyor’s surveyors between the 1780s and 1840 and formed the basis for the first publicly available One-Inch map.  They were drawn at scales of six inches to the mile for areas considered of particular military significance and down to two inches to the mile for other areas.  Fair copies were then produced from these preliminary drawings to one inch to the mile and then copper plates were prepared for printing.  The Draft Surveyors maps for the whole of Wales are now available online and they form an important part in the study of Welsh upland place-names as they bridge the time frame between the late 18^th century and the mid-19^th century when the Ordnance Survey produced their first One-Inch maps, and importantly for this hill and its listed name, this map gives the Welsh version, along with its English counterpart.

Extract from the Ordnance Survey Draft Surveyors map

The One-Inch ‘Old Series’ map was the first map that Ordnance Survey produced, and their publication culminated from the whole of Britain being surveyed between 1791 and 1874 and the detail gathered therein produced at a scale of one inch to the mile and published in sheet format between 1805 and 1874.  The One-Inch ‘Old Series’ maps for the whole of Wales are now available online; they are also available in map format as enlarged and re-projected versions to match the scale and dimensions of the Ordnance Survey 1:50,000 Landranger series and are published by Cassini.  This series of maps form another important part in the study of Welsh upland place-names and bridge the timeframe leading up to the production of the Ordnance Survey base map of the Six-Inch series, and again, this map gives the Welsh version of this name; Mynydd Llwyd, along with its English counterpart.

Extract from the Ordnance Survey One-Inch 'Old Series' map

The intricacies of language and prioritising one in favour of another for listing a hill is fraught with complication, with originating Cymraeg names being anglicised and also originating English names being cymricised, examples such as these are more common in border country and especially so for anglicised forms.  There is no steadfast rule that fits all, but as a standard a name that has its origins in the Welsh language should be prioritised in favour of a contemporary anglicised or English version of the name, and ideally for this to be substantiated by either historic documentation and / or contemporary usage.  Likewise, if a name exists where an element of it is in English and if this name applies to a hill that is situated in a Welsh speaking part of Wales it is standard practice to use a full Welsh term for the name.  It is also standard practice to use a Welsh name for a hill if another name exists that has originated in a different language.

Therefore, the name this hill is now listed by in the 200m Twmpau and Y Trechol – The Dominant Hills of Wales is Mynydd Llwyd, and this was derived from the Ordnance Survey Draft Surveyors map and the One-Inch ‘Old Series’ map, with the Welsh name for this hill prioritised over its English counterpart, which for listing purposes is standard practice.

The full details for the hill are:

Group:  Gwent Is Coed

Name:  Mynydd Llwyd

Previously Listed Name:  Gray Hill

OS 1:50,000 map:  171, 172

Summit Height:  275m (spot height)

Summit Grid Reference:  ST 43399 93559 (hand-held GPS via DoBIH)

Bwlch Height:  c 183m (interpolation)

Bwlch Grid Reference:  ST 42894 93984 (interpolation)

Drop:  c 92m (spot height summit and interpolated bwlch)

Dominance:  33.45% (spot height summit and interpolated bwlch)

Myrddyn Phillips (May 2020)

Mapping Mountains – Hill Reclassifications – Humps

Gray Hill (ST 433 935) – Subhump addition

This is the ninth in a series of Hill Reclassification posts that detail hills whose status has been altered in the listing of the Humps (HUndred Metre Prominences) through map study and / or surveys that I have instigated.

The hill name used in this and forthcoming posts is that used in the listing of Humps, therefore individual names and their composition may not match those that are used in listings I am directly associated with.  However, I am of firm belief that listed hill names used by other authors should be respected when giving detail within other people’s lists, however inappropriate some hill names may be considered.

This and forthcoming posts are retrospective as many of these hill reclassifications were initiated from studying the Ordnance Survey enlarged mapping that is hosted on the Geograph website, and for the reclassifications that affected the Humps the email I posted on the RHB Yahoo Group forum in relation to this hill was dated 18.05.12.

The listing of Humps was published in book format by Lulu in 2009 and entitled More Relative Hills of Britain, its author; Mark Jackson gives credit to a number of people who contributed toward the formation of this list, these include; Eric Yeaman, Alan Dawson, Clem Clements, Rob Woodall, Bernie Hughes, Pete Ridges and others.  When the list was published in book format there were 2987 Humps listed with their criteria being any British hill that has 100m or more of drop, accompanying the main list is a sub category entitled Subhumps, with the criteria being any British hill that has 90m or more and below 100m of drop.

More Relative Hills of Britain by Mark Jackson

The details for the reclassification appear below:

There has been an addition to the listing of the Humps (HUndred Metre Prominences) due to consulting the Ordnance Survey enlarged mapping that is hosted on the Geograph website, with these details being posted on the RHB Yahoo Group forum on 18.05.12.

Prior to this notification Mark Jackson had listed this hill with c 39m of drop based on the 273m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map (whilst the Ordnance Survey 1:50,000 Landranger map has a summit spot height of 275m which is the rounded metric equivalent of the 902ft height that appears on the Ordnance Survey Six-Inch map) and an estimated bwlch height of c 234m, with this latter height an obvious error as the bwlch contouring is between 180m – 185m.  The area of the bwlch benefits from having contour intervals at 5m and a 182m spot height on a road on the Ordnance Survey enlarged mapping on the Geograph website.  With this latter height or an estimated bwlch height of c 183m giving this hill c 90m – 91m of drop if the 273m summit height on the 1:25,000 map is followed, or alternatively c 92m – 93m of drop if the 275m summit height on the 1:50,000 map is followed, whichever value is chosen it is sufficient for this hill to be classified as a Subhump. 

Extract from the Ordnance Survey enlarged mapping hosted on the Geograph website that shows the 273m summit and 182m bwlch spot heights

The hill appears under the name of Gray Hill in the listing of the Humps, this name appears on current Ordnance Survey maps, but for its originator name the Ordnance Survey Draft Surveyors map and the Ordnance Survey One-Inch ‘Old Series’ map have to be consulted, and on each the name Mynydd Llwyd appears.  The Welsh name for this hill is considered more appropriate than its English counterpart (see Language sub heading under Prioritised Decision in the Naming Protocols within the Protocols for the Naming of Hills document).

Extract from the Ordnance Survey Draft Surveyors map giving the hill its Welsh name of Mynydd Llwyd

Extract from the Ordnance Survey One-Inch 'Old Series' map which also gives this hill its Welsh name of Mynydd Llwyd

The hill is adjoined to the Coed Gwent range of hills and is situated overlooking the Wentwood Reservoir which is to its south-west, with the village of Llanfaches (Llanvaches) towards the south.

The addition of this hill to Subhump status was accepted by Mark Jackson on the 19.07.12 and the listing of the Humps was updated accordingly.

The full details for the hill are:

Name:  Gray Hill (as listed in the Humps)

Summit Height:  273m (as listed in the Humps)

OS 1:50,000 map:  171, 172

OS 1:25,000 map:  14

Summit Grid Reference:  ST 43399 93559

Drop:  c 90m (as listed in the Humps)

Myrddyn Phillips (September 2017)