Mapping Mountains – Significant Name Changes – 30-99m Twmpau

 

Parc Penrhyn (SH 601 720) 

There has been a Significant Name Change to a hill that is listed in the 30-99m 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 Parc Penrhyn (SH 601 720)

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

30-99m Twmpau – Welsh hills at or above 30m and below 100m in height that have 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or above 30m and below 100m 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. 

30-99m Twmpau by Myrddyn Phillips

The hill is adjoined to the Glyder Fawr group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A5 road to its west and the A55 road to its south-east, and has the city of Bangor towards the west.

When the original 30-99m 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-evaluated and it was listed under the transposed name of Penrhyn Castle, which is a prominent name that appears adjacent to the summit of this hill on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, with the land where the castle is situated named as Penrhyn Park on the 1:25,000 Explorer map.  With its numerical details given as an estimated c 19m of drop, based on an estimated c 53m summit height and an estimated c 34m bwlch height, with both heights based on interpolation of 10m contouring. 

Extract from the Ordnance Survey 1:25,000 Explorer 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 and where this is substantiated by either historic documentation and/or contemporary usage should be prioritised in favour of a contemporary anglicised or English version of the name.  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 30-99m Twmpau is Parc Penrhyn, with this name prioritised over the mixed language name favoured on the contemporary Ordnance Survey 1:25,000 Explorer map and the land name favoured over that of the castle name. 

 

The full details for the hill are:

Group:  Glyder Fawr

Name:  Parc Penrhyn

Previously Listed Name:  Penrhyn Castle 

OS 1:50,000 map:  115

Summit Height:  56.5m (LIDAR) 

Summit Grid Reference:  SH 60179 72091 (LIDAR)               

Bwlch Height:  31.5m (LIDAR) 

Bwlch Grid Reference:  SH 60168 71662 (LIDAR) 

Drop:  25.1m (LIDAR) 

 

Myrddyn Phillips (March 2025)

 

 

Mapping Mountains – Significant Height Revisions – 30-99m Twmpau

Parc Penrhyn (SH 601 720) 

There has been a Significant Height Revision to a hill that is listed in the 30-99m 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 Parc Penrhyn (SH 601 720)

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

30-99m Twmpau – Welsh hills at or above 30m and below 100m in height that have 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or above 30m and below 100m 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. 

30-99m Twmpau by Myrddyn Phillips

The name the hill is listed by is Parc Penrhyn, and it is adjoined to the Glyder Fawr group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A5 road to its west and the A55 road to its south-east, and has the city of Bangor towards the west.

When the original 30-99m 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-evaluated and it was listed with an estimated c 19m of drop, based on an estimated c 53m summit height and an estimated c 34m bwlch height, with both heights based on interpolation of 10m contouring. 

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 Parc Penrhyn (SH 601 720)

The summit height produced by LIDAR analysis is 56.5m and is positioned at SH 60179 72091, 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 56.5m and this was derived from LIDAR analysis, this is 3.5m higher than the previously listed summit height of c 53m, which was based on interpolation of its uppermost 50m ring contour that appears on the Ordnance Survey 1:25,000 Explorer map.

The full details for the hill are:

Group:  Glyder Fawr 

Name:  Parc Penrhyn 

OS 1:50,000 map:  115

Summit Height (New Height):  56.5m (LIDAR) 

Summit Grid Reference:  SH 60179 72091 (LIDAR)               

Bwlch Height:  31.5m (LIDAR) 

Bwlch Grid Reference:  SH 60168 71662 (LIDAR) 

Drop:  25.1m (LIDAR) 

 

Myrddyn Phillips (March 2025)

 

  

Mapping Mountains – Hill Reclassifications – 30-99m Twmpau

 

Parc Penrhyn (SH 601 720) – 30-99m Sub-Twmpau addition 

There has been an addition to the list of 30-99m 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 Parc Penrhyn (SH 601 720)

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

30-99m Twmpau – Welsh hills at or above 30m and below 100m in height that have 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or above 30m and below 100m 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. 

30-99m Twmpau by Myrddyn Phillips

The name the hill is listed by is Parc Penrhyn, and it is adjoined to the Glyder Fawr group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A5 road to its west and the A55 road to its south-east, and has the city of Bangor towards the west.

When the original 30-99m 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-evaluated and it was listed with an estimated c 19m of drop, based on an estimated c 53m summit height and an estimated c 34m bwlch height, with both heights based on interpolation of 10m contouring. 

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 addition of this hill to 30-99m Sub-Twmpau status is due to LIDAR analysis, resulting in a 56.5m summit height and a 31.5m bwlch height, with these values giving this hill 25.1m of drop, which is sufficient for it to be classified as a 30-99m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Glyder Fawr 

Name:  Parc Penrhyn 

OS 1:50,000 map:  115

Summit Height:  56.5m (LIDAR) 

Summit Grid Reference:  SH 60179 72091 (LIDAR)               

Bwlch Height:  31.5m (LIDAR) 

Bwlch Grid Reference:  SH 60168 71662 (LIDAR) 

Drop:  25.1m (LIDAR) 

 

Myrddyn Phillips (March 2025)