Mapping Mountains – Significant Height Revisions – Y Trichant – The 300m Hills of Wales

 

Lan Ddu (SN 716 388) 

There has been a Significant Height Revision to a hill that is listed in the Y Trichant – The 300m 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 Myrddyn Phillips. 

LIDAR image of Lan Ddu (SN 716 388)

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

Y Trichant – The 300m Hills of Wales – Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant, with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13^th May 2017, and the Introduction to the Mapping Mountains publication of the list appearing on the 1^st January 2022. 

Y Trichant - The 300m Hills of Wales by Myrddyn Phillips

The name the hill is now listed by is Lan Ddu, and this was confirmed from the Ordnance Survey series of Six-Inch maps, and it is adjoined to the Mynydd Mallaen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north-west, west and south, and the A482 road farther to its south-west, and has the town of Llanymddyfri (Llandovery) towards the south-east.

When the original 300m 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 359m summit height, based on the spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.

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 74m of drop, based on the 359m summit spot height and the 285m 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. 

LIDAR summit image of Lan Ddu (SN 716 388)

The summit height produced by LIDAR analysis is 356.9m and is positioned at SN 71669 38863, 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 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 356.9m and this was derived from LIDAR analysis, this is 2.1m lower than the previously listed 359m summit height, which was based on the spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

 

The full details for the hill are: 

Group:  Mynydd Mallaen 

Name:  Lan Ddu 

OS 1:50,000 map:  146, 160

Summit Height (New Height):  356.9m (LIDAR)                                                           

Summit Grid Reference:  SN 71669 38863 (LIDAR) 

Bwlch Height:  284.6m (LIDAR) 

Bwlch Grid Reference:  SN 71732 39915 & SN 71728 39925 (LIDAR) 

Drop:  72.3m (LIDAR) 

 

Myrddyn Phillips (November 2025)

Mapping Mountains – Significant Name Changes – Y Trichant – The 300m Hills of Wales

Lan Ddu (SN 716 388) 

There has been a Significant Name Change to a hill that is listed in the Y Trichant – The 300m 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 Myrddyn Phillips. 

LIDAR image of Lan Ddu (SN 716 388)

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

Y Trichant – The 300m Hills of Wales – Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant, with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13^th May 2017, and the Introduction to the Mapping Mountains publication of the list appearing on the 1^st January 2022. 

Y Trichant - The 300m Hills of Wales by Myrddyn Phillips

The hill is adjoined to the Mynydd Mallaen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north-west, west and south, and the A482 road farther to its south-west, and has the town of Llanymddyfri (Llandovery) towards the south-east.

The hill appeared in the original 300m height band of Welsh P30 hills published on Geoff Crowder’s v-g.me website, under the directional name of Lan-ddu North-East Top, with an accompanying note stating; Name from hill to the South-West.

Lan-ddu North-East Top

359m

SN717388

146/160

187

Name from hill to the South-West

During my early hill listing I thought it appropriate to either invent a name for a hill, or use a name that appeared near to the summit of the hill on Ordnance Survey maps of the day.  My preference was to use farm names and put Pen, Bryn or Moel in front of them or as in this instance use a directional name based on supplanting the name of a near hill and adding a directional component to it.  This is not a practice that I now advocate as with time and inclination place-name data can be improved either by asking local people or by examining historic documents, through this form of research an appropriate name for the hill can usually be found.

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

Since the original publication of the Welsh P30 lists on Geoff Crowder’s v-g.me website there have been a number of 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 were digitally updated such as the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map, whilst others are current and digitally updated such as the interactive mapping on the Magic Maps and WalkLakes websites, and it is the series of Ordnance Survey Six-Inch maps that form the basis of the change in the listed name of this hill.

Extract from the Ordnance Survey series of Six-Inch maps

The Ordnance Survey series of Six-Inch maps formed the base map Ordnance Survey used for many decades leading to the production of the 1:10,000 Series of maps, both have now been superseded by the digitised Master Map.  The series of Six-Inch maps are excellent for name placement and especially so compared to the contemporary Ordnance Survey 1:25,000 Explorer map, and it is the series of Six-Inch maps that position the name of Lan Ddu also taking in land incorporating this hill.

Therefore, the name this hill is now listed by in the Y Trichant – The 300m Hills of Wales is Lan Ddu and this was derived from the Ordnance Survey series of Six-Inch maps. 

 

The full details for the hill are: 

Group:  Mynydd Mallaen 

Name:  Lan Ddu 

Previously Listed Name:  Lan-ddu North-East Top 

OS 1:50,000 map:  146, 160

Summit Height:  356.9m (LIDAR)                                                           

Summit Grid Reference:  SN 71669 38863 (LIDAR) 

Bwlch Height:  284.6m (LIDAR) 

Bwlch Grid Reference:  SN 71732 39915 & SN 71728 39925 (LIDAR) 

Drop:  72.3m (LIDAR) 

 

Myrddyn Phillips (June 2023)