Myrddyn Phillips - Mapping Mountains: Garden Field

Showing posts with label Garden Field. Show all posts

Friday, 20 March 2020

Mapping Mountains – Significant Height Revisions – 100m Twmpau

Garden Field (SO 180 383)

There has been a Significant Height Revision to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Garden Field (SO 180 383)

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

100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m 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 name the hill is now listed by is Garden Field and this derived from the Tithe map, and it is adjoined to the Mynyddoedd Duon group of hills which are situated in the eastern part of South Wales (Region C, Sub-Region C3), and it is encircled by minor roads with the Afon Gwy (River Wye) and the A438 road further to its north-west, and the village of Aberllynfi (Three Cocks) towards the south-west.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was listed with a 168m summit height based on the spot height 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.

The height produced by LIDAR analysis is 170.3m and is positioned at SO 18079 38331, this is not a substantial revision compared to some revised heights, but it does come 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 summit 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, this hill’s new listed summit height is 170.3m and this was derived from LIDAR analysis, this is 2.3m higher than the previously listed summit height of 168m which was based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map.

The full details for the hill are:

Group: Mynyddoedd Duon

Name: Garden Field

OS 1:50,000 map: 161

Summit Height (New Height): 170.3m (LIDAR)

Summit Grid Reference: SO 18079 38331 (LIDAR)

Bwlch Height: 141.3m (LIDAR)

Bwlch Grid Reference: SO 18629 38227 (LIDAR)

Drop: 28.9m (LIDAR)

Myrddyn Phillips (March 2020)

Monday, 16 March 2020

Mapping Mountains – Significant Name Changes – 100m Twmpau

Garden Field (SO 180 383)

There has been a Significant Name Change to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height, their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Garden Field (SO 180 383)

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

The hill is adjoined to the Mynyddoedd Duon group of hills which are situated in the eastern part of South Wales (Region C, Sub-Region C3), and it is encircled by minor roads with the Afon Gwy (River Wye) and the A438 road further to its north-west, and the village of Aberllynfi (Three Cocks) towards the south-west.

The hill originally appeared in the 100m P30 list on Geoff Crowder’s v-g.me website under a transposed name of Allt y Fran, which is a prominent name that Ordnance Survey have consistently positioned in a forested section of land to the east of this hill’s summit.

Allt y Fran

168m

SO181384

161

171m on 1984 1:50000 map.

During my early hill listing I paid little regard to name placement on the map, or the meaning of names and to what feature the name was appropriately applied to. Therefore I prioritised names for listing purposes that I now understand are either inappropriate or where another name is viewed as being more appropriate.

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

As this hill comprises bounded land the Tithe map was consulted. 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 18 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 Garden Field in the apportionments, with the details on the Tithe map appearing in the parish of Aberllunvy [sic] and in the county named as Brecon.

Extract from the apportionments

Therefore, the name this hill is now listed by in the 100m Twmpau is Garden Field, and this was derived from the Tithe map.