Myrddyn Phillips - Mapping Mountains: Bryn (SH 782 798)

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Tuesday, 25 June 2024

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

Bryn (SH 782 798)

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 Bryn (SH 782 798)

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, 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 Mynydd Hiraethog group of hills, which are situated in the northern part of North Wales (Region A, Sub-Region A2), and it is positioned with the A546 road to its west and the B5115 road to its south-east, and has the town of Deganwy towards the north.

The hill appeared in the original Welsh 30-99m P30 list on Geoff Crowder’s v-g.me website, under the transposed name of Deganwy, with an accompanying note stating; Name from surrounding district.

Deganwy

90m

SH782799

115

Name from surrounding district

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 transpose the name of a town and use it for that of the hill. 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 176 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 Bryn in the apportionments, with the details on the Tithe map appearing in the parish of Eglwys Rhos and with the county unnamed.

Extract from the apportionments

Therefore, the name this hill is now listed by in the 30-99m Twmpau is Bryn, and this was derived from the Tithe map.

The full details for the hill are:

Group: Mynydd Hiraethog

Name: Bryn

Previously Listed Name: Deganwy

OS 1:50,000 map: 115

Summit Height: 87.2m (LIDAR)

Summit Grid Reference: SH 78234 79892 (LIDAR)

Bwlch Height: 65.6m (LIDAR)

Bwlch Grid Reference: SH 78372 79790 (LIDAR)

Drop: 21.6m (LIDAR)

Myrddyn Phillips (June 2024)

Tuesday, 18 June 2024

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

Bryn (SH 782 798)

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 Bryn (SH 782 798)

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, 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 now listed by is Bryn and this was derived from the Tithe map, and it is adjoined to the Mynydd Hiraethog group of hills, which are situated in the northern part of North Wales (Region A, Sub-Region A2), and it is positioned with the A546 road to its west and the B5115 road to its south-east, and has the town of Deganwy towards the north.

When the original 30-99m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list with a summit height of 90m, based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map.

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 23m of drop, based on the 90m summit spot height and an estimated c 67m bwlch height, based on interpolation of 5m contouring between 65m – 70m.

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 Bryn (SH 782 798)

The summit height produced by LIDAR analysis is 87.2m and is positioned at SH 78234 79892, 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 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, the new listed summit height of this hill is 87.2m and this was derived from LIDAR analysis, this is 2.8m lower than the previously listed summit height of 90m, which was based on the spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map.