Mapping Mountains – Significant Name Changes – 200m Twmpau

 

Diosgydd (SH 775 579) 

There has been a Significant Name Change to a hill that is listed in the 200m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail produced by Joe Nuttall in his surface analysis programme, with subsequent LIDAR analysis conducted by the DoBIH team and independently by Myrddyn Phillips. 

LIDAR image of Diosgydd (SH 775  579)

The criteria for the list that this name change applies to 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, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 200m Twmpau 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 A, Sub-Region A1), and it is positioned encircled by minor roads, with the A5 road farther to its south-west, and has the town of Betws-y-coed towards the south-east.

The hill appeared in the original Welsh 200m P30 list on Geoff Crowder’s v-g.me website, under the invented and transposed name of Bryn Diosgydd, with an accompanying note stating; Name from buildings to the West.

Bryn Diosgydd

233m

SH775579

115

17

Name from buildings to the 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; as was done in this instance.  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

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 16 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 as Diosgau in the apportionments, with the details on the Tithe map appearing in the parish of 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 200m Twmpau is Diosgydd, which is the prioritised plural of this name and this was derived from the Tithe map. 

 

The full details for the hill are:

Group:  Carnedd Llywelyn

Name:  Diosgydd

Previously Listed Name:  Bryn Diosgydd   

OS 1:50,000 map:  115

Summit Height:  233.05m (LIDAR) 

Summit Grid Reference:  SH 77503 57940 (LIDAR) 

Bwlch Height:  202.85m (LIDAR) 

Bwlch Grid Reference:  SH 77793 57796 (LIDAR) 

Drop:  30.2m (LIDAR) 

 

Myrddyn Phillips (October 2023)

 

 

 

 

 

 

Mapping Mountains – Hill Reclassifications – 200m Twmpau

Diosgydd (SH 775 579) – 200m Sub-Twmpau reclassified to 200m Twmpau

There has been a reclassification to the list of 200m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail produced by Joe Nuttall in his surface analysis programme, with subsequent LIDAR analysis conducted by the DoBIH team and independently by Myrddyn Phillips. 

LIDAR image of Diosgydd (SH 775 579)

The criteria for the list that this reclassification applies to 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, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 200m Twmpau by Myrddyn Phillips

The name the hill is now listed by is Diosgydd and this was derived from the Tithe map, and it is adjoined to the Carnedd Llywelyn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned encircled by minor roads, with the A5 road farther to its south-west, and has the town of Betws-y-coed towards the south-east.

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 accompanying Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 category.

When 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 28m of drop, based on the 233m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 205m bwlch height, based on interpolation of 10m contouring between 200m – 210m. 

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 reclassification of this hill from 200m Sub-Twmpau status is due to LIDAR analysis, resulting in a 233.05m summit height and a 202.85m bwlch height, with these values giving this hill 30.2m of drop, which is sufficient for it to be classified as a 200m Twmpau. 

 

The full details for the hill are: 

Group:  Carnedd Llywelyn 

Name:  Diosgydd 

OS 1:50,000 map:  115

Summit Height:  233.05m (LIDAR) 

Summit Grid Reference:  SH 77503 57940 (LIDAR) 

Bwlch Height:  202.85m (LIDAR) 

Bwlch Grid Reference:  SH 77793 57796 (LIDAR) 

Drop:  30.2m (LIDAR) 

 

Myrddyn Phillips (October 2023)