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

 

Aston Hill (SO 296 900) 

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 LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Aston Hill (SO 296 900)

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 listed by is Aston Hill, and it is adjoined to the Cilfaesty group of hills, which are situated in the north-eastern part of South Wales (Region C2, Sub-Region C2B), and it is positioned encircled by minor roads, with the B4385 road farther to its north-east, and has the town of Bishop’s Castle towards its 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 listed with a 379m summit height based on the spot height positioned at SO 29659 90041 that appears on the Ordnance Survey 1:25,000 Explorer 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 Aston Hill (SO 296 900)

The summit height produced by LIDAR analysis is 380.0m positioned at SO 29663 90049, 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 380.0m and this was derived from LIDAR analysis, this is 1.0m higher than the previously listed summit height of 379m, which was based on the spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map, and importantly indicates that this map is missing an uppermost 380m ring contour.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Cilfaesty

Name:  Aston Hill

OS 1:50,000 map:  137

Summit Height (New Height):  380.0m (LIDAR)

Summit Grid Reference:  SO 29663 90049 (LIDAR)  

Bwlch Height:  341.8m (LIDAR)

Bwlch Grid Reference:  SO 28966 89594 (LIDAR)

Drop:  38.2m (LIDAR)

 

Myrddyn Phillips (September 2026)

Mapping Mountains – Significant Name Changes – The Welsh P15s

Aber y Llyn (SH 792 584) 

There has been a Significant Name Change to a hill that is listed in The Welsh P15s, 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 Aber y Llyn (SH 792 584)

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

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The hill is adjoined to the Carnedd Llywelyn group of hills, which are situated in the north-western part of North Wales (Region C1, Sub-Region C1A), and it is positioned with minor roads to its west, the A5 road to its south, and the B5106 road and the A470 road to its east, and has the village of Betws-y-coed towards the south.

When the listing that became known as The Welsh P15s was being compiled, this hill was listed under the point (Pt. 242m) notation, with an estimated c 16m of drop, based on the 242m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 226m bwlch height, based on interpolation of 10m contouring between 220m – 230m. 

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

As the summit of this hill comprises bounded land the details for it were examined on the Tithe map.  The term Tithe map is generally given to a map of a Welsh or English parish or township and which was prepared after the 1836 Tithe Commutation Act.  This act allowed tithes to be paid in cash rather than goods.  The Tithe maps gave names of owners and occupiers of land in each parish and importantly for place-name research they also included the name of enclosed land.  This enclosed land is usually based on a field system, however not every field is given a name, but many are and especially so in Wales. 

Extract from the Tithe map

The enclosed land where the summit of this hill is situated is given the number 12a on the Tithe map, this can be cross referenced against the apportionments; it is these apportionments that give the name of the owner or occupier of the land as well as the name of the land.  The land where the summit of this hill is situated is named Aber y Llyn in the apportionments, with the details on the Tithe map appearing in the parish named as Betws-y-coed and in the county named as Caernarfonshire. 

Extract from the apportionments

Therefore, the name this hill is now listed by in the The Welsh P15s is Aber y Llyn, and this was derived from the Tithe map. 

 

The full details for the hill are: 

Group:  Carnedd Llywelyn 

Name:  Aber y Llyn 

Previously Listed Name:  Pt. 242m 

OS 1:50,000 map:  115

Summit Height:  240.9m (LIDAR)                                                           

Summit Grid Reference:  SH 79203 58436 (LIDAR)                                                  

Bwlch Height:  225.8m (LIDAR) 

Bwlch Grid Reference:  SH 79153 58238 (LIDAR) 

Drop:  15.0m (LIDAR) 

 

Myrddyn Phillips (September 2026) 

Mapping Mountains – Significant Height Revisions – 500m Twmpau and The Welsh Highlands – Uchafion Cymru

Pt. 574.9m (SH 663 500) 

There has been a Significant Height Revision that is retrospective to a hill that is listed in the 500m Twmpau and The Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a TrimbleGeoXH 6000 survey conducted by Aled Williams. 

Pt. 574.9m (SH 663 500).  Photo: Aled Williams

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

500m Twmpau – Welsh hills at or above 500m and below 600m in height that have 30m minimum drop, with an accompanying sub category entitled the 500m Sub-Twmpau consisting of all Welsh hills at or above 500m and below 600m in height that have 20m or more and below 30m of drop.  With the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.  The list is authored by Myrddyn Phillips and is published on Mapping Mountains in Google Doc format.

500m Twmpau by Myrddyn Phillips

The Welsh Highlands – Uchafion Cymru – Welsh hills at or above 500m in height with 15m minimum drop, with an accompanying sub list entitled the Welsh Highland Subs, the criteria for which is all Welsh hills at or above 500m in height with 10m or more and below 15m of drop.  This list is authored by Myrddyn Phillips and Aled Williams with the Introduction to the list published on Mapping Mountains in November 2015 and the latest update relating to the list published on Mapping Mountains in January 2023.

The Welsh Highlands - Uchafion Cymru by Aled Williams and Myrddyn Phillips

The hill is being listed by the point (Pt. 574.9m) notation and it is adjoined to the Moelwyn Mawr group of hills, which are situated in the north-western part of North Wales (Region C1, Sub-Region C1A), and it is positioned with the A498 road to its north-west, a minor road to its west and the A470 road to its east, and has the town of Blaenau Ffestiniog towards the south-east.

When the listings of the 500m Twmpau and The Welsh Highlands – Uchafion Cymru were first compiled, this hill was listed with an estimated summit height of c 578m, based on a 70ft (21.3m) basic levelling survey conducted by Myrddyn Phillips and interpolation of 10m contouring that appears on the Ordnance Survey 1:25,000 Explorer map. 

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

However, it was not until the survey with the Trimble GeoXH 6000 that the details for this hill could be accurately re-assessed.  This survey gives the summit of this hill as 574.9m positioned at SH 66301 50001, 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 other GNSS equipment 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. 

The Trimble GeoXH 6000 gathering data at the summit of Pt. 574.9m (SH 663 500).  Photo: Aled Williams

Therefore, the new listed summit height of this hill is 574.9m and this was derived from a Trimble GeoXH 6000 survey, this is 3.1m lower than the originally listed summit height of c 578m, which was based on a 70ft (21.3m) basic levelling survey conducted by Myrddyn Phillips and interpolation of 10m contouring that appears on the Ordnance Survey 1:25,000 Explorer map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Moelwyn Mawr

Name:  Pt. 574.9m

OS 1:50,000 map:  115

Summit Height (New Height):  574.9m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 66301 50001 

Bwlch Height:  552.9m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SH 66287 50113

Drop:  22.0m

 

Myrddyn Phillips and Aled Williams (September 2026)

 

Mapping Mountains – Summit Relocations – The Fours – The 400m Hills of England

 

Buttern Hill (SX 652 885) 

There has been a Summit Relocation 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 Buttern Hill (SX 652 885)

The criteria for the list that this summit relocation 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 Buttern Hill, 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 a series of minor roads towards its east, and has the town of Chagford towards the 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 18m of drop, based on the 413m summit spot height positioned at SX 65283 88668 that appears on the Ordnance Survey 1:25,000 Explorer map and the 395m 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.  With the caveat that the Ordnance Survey 1:50,000 Landranger map has a 413m spot height positioned at SX 65308 88423. 

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 Buttern Hill (SX 652 885)

LIDAR analysis gives the highest ground on this hill as 414.3m positioned at SX 65272 88551, and when compared to its originally listed summit position this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour either on Ordnance Survey maps or interactive mapping, to a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is considered a relatively recent man-made construct, or the listing of a new twin summit or de-twinning of a summit, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist.

Therefore, the summit height produced by LIDAR analysis is 414.3m and this is positioned at SX 65272 88551.  This position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and is approximately 117 metres southward from where the originally listed summit is positioned.

 

The full details for the hill are:

Group:  High Willhays

Name:  Buttern Hill

OS 1:50,000 map:  191

Summit Height:  414.3m (LIDAR)

Summit Grid Reference (New Position):  SX 65272 88551 (LIDAR)

Col Height:  395.9m (LIDAR)

Col Grid Reference:  SX 64912 88541 (LIDAR)

Drop:  18.3m (LIDAR)

 

Myrddyn Phillips and Aled Williams (September 2026)

Mapping Mountains – Hill Reclassifications – 500m Twmpau

 

Llechwedd Deiliog (SH 785 398) – 500m Sub-Twmpau addition

There has been confirmation of an addition to the listing of the 500m Twmpau that is retrospective, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and Aled Williams and subsequent LIDAR analysis conducted by Aled Williams. 

LIDAR image of Llechwedd Deiliog (SH 785 398)

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

500m Twmpau - Welsh hills at or above 500m and below 600m in height with 30m minimum drop, with an accompanying sub list entitled the 500m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 500m and below 600m 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.  The list is authored by Myrddyn Phillips and is available to download in Google Doc format from Mapping Mountains.

500m Twmpau by Myrddyn Phillips

The name the hill is listed by is Llechwedd Deiliog and it is adjoined to the Arenig Fach group of hills, which are situated in the central part of North Wales (Region C1, Sub-Region C1A), and it is positioned with the B4391 road to its south, and has the village of Trawsfynydd towards the west south-west. 

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

When the list that later became known as the 500m Twmpau was first compiled, this hill was not included in the accompanying sub list, but was later added after a basic levelling survey conducted by Myrddyn Phillips on the 16.05.04 gave it 66½ft (20.3m drop).

This hill is also included in the listing of The Welsh Highlands – Uchafion Cymru co-authored by Myrddyn Phillips and Aled Williams and it formed one of a number of hills held back from publication until this list was published in its entirety.  However, this policy has now changed; therefore the details for this hill have been put in the public domain. 

The Trimble set-up position at SH 78452 39920 with subsequent LIDAR analysis prioritised

However, it was not until a Trimble GeoXH 6000 survey and 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. 

The Trimble GeoXH 6000 gahering data at the bwlch of Llechwedd Deiliog

Therefore, the confirmation of the addition of this hill to 500m Sub-Twmpau status is due to a Trimble GeoXH 6000 survey and LIDAR analysis, resulting in a 501.7m summit height and a 481.2m bwlch height, with these values giving this hill 20.6m of drop, which is insufficient for it to be classified as a 500m Sub-Twmpau.

 

The full details for the hill are:

Group:  Arenig Fach

Name:  Llechwedd Deiliog

OS 1:50,000 map:  124

Summit Height:  501.7m (LIDAR) 

Summit Grid Reference:  SH 78522 39815 (LIDAR) 

Bwlch Height:  481.2m (converted to OSGM15, Trimble GeoXH 6000) 

Bwlch Grid Reference:  SH 78298 40196 (Trimble GeoXH 6000) 

Drop:  20.6m (LIDAR summit and Trimble GeoXH 6000 bwlch)

Myrddyn Phillips (September 2026)