Mapping Mountains – Summit Relocations – 100m Twmpau

Five Acres (SS 537 932)

There has been a Summit Relocation to a hill that is listed in the 100m Twmpau, with the summit height, drop and status of the hill being confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Five Acres

The criteria for the list that this summit relocation 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 of the bounded land where the natural summit of this hill is situated is Five Acres and this was derived from the Tithe map, and it is the name that this hill is now listed by.  The hill is adjoined to the Gŵyr group of hills, which are situated in the western part of South Wales (Region C, Sub-Region C1), and it is positioned between the B roads of the 4295 to the north-west and 4271 to the south, and has the village of Pen-clawdd towards the north.

If wanting to visit the hill permission to do so should be sought as the summit area is not a part of designated open access land, for those wishing to do so the nearest public footpath is to its south, with other possibilities via gated fields to the east.

Prior to LIDAR analysis this hill was listed with an estimated c 43m drop, with an estimated c 127m summit height based on an uppermost 125m ring contour and an estimated c 84m bwlch height based on interpolation of 5m contouring between 80m – 85m on the Ordnance Survey 1:25,000 Explorer map. 

The summit height produced by 1m DTM LIDAR analysis is 125.1m (125.059m) and this height is given to four separate points, these are positioned at SS 53779 93281 and SS 53779 93291 and SS 53774 93296 and SS 53780 93297.  LIDAR contouring indicates that these positions are a part of the existing natural summit of the hill, whilst also indicating that a higher point exists; 125.2m (125.190m) at SO 53791 93318 which is a part of a raised field boundary which is considered a relatively recent man-made construct, therefore it is the position of the natural summit that is being listed for this hill.  As the raised field boundary is higher than the natural summit of the hill this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The position of the natural summit of Five Acres

The position of the high point of the raised field boundary

The term Summit Relocations applies to any listed hill whose summit meets the following criteria; where there are a number of potential summit positions within close proximity and the highest point is not where previously given, 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, or when the summit of the hill is in a different field compared to where previously given, or when the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary that is judged to be a relatively recent man-made construct.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 Explorer map is being prioritised in favour of the 1:50,000 Landranger map for detailing these relocations.

LIDAR image of the summit area of Five Acres with the field boundary's being distinctly shown

Close-up LIDAR image of the summit of Five Acres

The summit height produced by 1m DTM LIDAR analysis is 125.1m (125.059m) and this height is given to four separate points, these are positioned at SS 53779 93281 and SS 53779 93291 and SS 53774 93296 and SS 53780 93297.  These positions are a part of the natural summit of the hill and not given a spot height on Ordnance Survey maps, they are approximately 40 metres from the raised field boundary that LIDAR gives as higher, but this point is considered a relatively recent man-made construct.  

The full details for the hill are:

Group:  Gŵyr

Name:  Five Acres

OS 1:50,000 map:  159

Summit Height:  125.1m (LIDAR)

Summit Grid Reference:  SS 53779 93281 and SS 53779 93291 and SS 53774 93296 and SS 53780 93297 (LIDAR, natural summit) (LIDAR gives a 125.2m high raised field boundary positioned at SS 53791 93318 which is considered a relatively recent man-made construct)

Bwlch Height:  84.3m (LIDAR)

Bwlch Grid Reference:  SS 56307 93757 (LIDAR)

Drop:  40.8m (LIDAR)

Myrddyn Phillips (November 2018)

Mapping Mountains – Significant Name Changes – 100m Twmpau

Five Acres (SS 537 932)

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

LIDAR image of Five Acres

The criteria for the list that this name change 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 hill is adjoined to the Gŵyr group of hills, which are situated in the western part of South Wales (Region C, Sub-Region C1), and it is positioned between the B roads of the 4295 to the north-west and 4271 to the south, and has the village of Pen-clawdd towards the north.

The hill originally appeared in the 100m P30 list on Geoff Crowder’s v-g.me website under the directional name of Mynydd-Bach-y-Cocs West Top with an accompanying note stating; Name from hill to the East.

 

Mynydd-Bach-y-Cocs West Top

125c

SS538933

159

164

Name from hill to the East

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 use a directional name based on what I presumed was a separate named hill to the east.  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 1:50,000 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 330 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 Five Acres in the apportionments, with the details on the Tithe map appearing in the parish of Llanrhidian and in the county named as Glamorgan.

Extract from the apportionments

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

The full details for the hill are:

Group:  Gŵyr

Name:  Five Acres

Previously Listed Name:  Mynydd-Bach-y-Cocs West Top

  

Summit Height:  125.1m (LIDAR)

OS 1:50,000 map:  159

Summit Grid Reference:  SS 53779 93281 and SS 53779 93291 and SS 53774 93296 and SS 53780 93297 (LIDAR, natural summit) (LIDAR gives a 125.2m high raised field boundary positioned at SS 53791 93318 which is considered a relatively recent man-made construct) 

Drop:  40.8m (LIDAR)

Myrddyn Phillips (November 2018)

Mapping Mountains – Hill Reclassifications – Y Trechol – The Dominant Hills of Wales

Five Acres (SS 537 932) – Lesser Dominant deletion

There has been a deletion to the listing of Y Trechol – The Dominant Hills of Wales due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

Y Trechol – The Dominant Hills of Wales - Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With an accompanying sub list entitled Y Trechol - The Lesser Dominant Hills of Wales, with the criteria for this sub category being those additional Welsh P30 hills whose prominence is 33% or more and below 50% of their absolute height.

Prior to LIDAR analysis this hill was listed with 33.86% dominance based on an estimated c 43m drop value, with an estimated c 127m summit height based on an uppermost 125m ring contour and an estimated c 84m bwlch height based on interpolation of 5m contouring between 80m – 85m on the Ordnance Survey 1:25,000 Explorer map. 

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

The bounded land where the summit of this hill is situated is named Five Acres on the Tithe map and this is the name the hill is now listed by.  The hill is adjoined to the Gŵyr group of hills, which are situated in the western part of South Wales (Region C, Sub-Region C1), and is positioned between the B roads of the 4295 to the north-west and 4271 to the south, and has the village of Pen-clawdd towards the north.

If wanting to visit the hill permission to do so should be sought as the summit area is not a part of designated open access land, for those wishing to do so the nearest public footpath is to its south, with other possibilities via gated fields to the east.

The deletion of Five Acres from Lesser Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips.   The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR image of the summit of Five Acres with the natural summit shown and the field boundary's being prominent on the image

LIDAR image of Five Acres

The 1m DTM LIDAR analysis gives the hill the following details:

Name:  Five Acres

Summit Height:  125.1m (natural summit)

Summit Grid Reference:  SS 53779 93281 and SS 53779 93291 and SS 53774 93296 and SS 53780 93297 (natural summit) (LIDAR gives a 125.2m high raised field boundary positioned at SS 53791 93318 which is considered a relatively recent man-made construct)

Bwlch Height:  84.3m

Bwlch Grid Reference:  SS 56307 93757

Drop:  40.8m

Dominance:  32.59%

Therefore, the 125.1m LIDAR analysis for the summit gives four positions of equal height at SS 53779 93281 and SS 53779 93291 and SS 53774 93296 and SS 53780 93297 and the 84.3m LIDAR analysis for the bwlch position at SN 56307 93757 gives this hill 40.8m of drop and 32.59% dominance, with is insufficient for Lesser Dominant status.

The full details for the hill are:

Group:  Gŵyr

Name:  Five Acres

Dominance:  32.59% (LIDAR)

OS 1:50,000 map:  159

Summit Grid Reference:  SS 53779 93281 and SS 53779 93291 and SS 53774 93296 and SS 53780 93297 (LIDAR) 

Summit Height:  125.1m (LIDAR)

Bwlch Grid Reference:  SS 56307 93757 (LIDAR)

Drop Summit to Bwlch:  40.8m (LIDAR)

Drop Bwlch to ODN:  84.3m (LIDAR)

Myrddyn Phillips (November 2018)