Mapping Mountains – Hill Reclassifications – 100m Twmpau

Clytiau Poethion (SH 763 717) – 100m Twmpau addition

There has been an addition of a hill that is now listed in the 100m Twmpau, with the summit height and its location, the drop and status of the hill confirmed by LIDAR analysis, and a subsequent summit survey with the Trimble GeoXH 6000, both conducted by Myrddyn Phillips with the latter taking place on the 10^th October 2018.

LIDAR image of Clytiau Poethion and Maes Glas Mawr

The criteria for the list that this reclassification 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 summit of this hill is situated is Clytiau Poethion, and this was derived from the Tithe map and it is the name that this hill is now listed by, and it is adjoined to the Carneddau group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and the hill is encircled by minor roads with the B5106 and the Afon Conwy (River Conwy) to its east, and has the town of Conwy to its north.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website the adjacent northerly hill known as Maes Glas Mawr (SH 76876 72414) was included in the main P30 list as its summit was thought to be higher than that of Clytiau Poethion (SH 76337 71799).

However, it was not until LIDAR became available that the details for each 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.  

Importantly LIDAR analysis gave Clytiau Poethion as higher than Maes Glas Mawr and this has subsequently been confirmed by a Trimble GeoXH 6000 survey, therefore the bylchau for each hill is swapped as are their classifications, resulting in a Trimble GeoXH 6000 summit height for Clytiau Poethion of 109.1m positioned at SH 76337 71799, and a bwlch height of 68.7m produced by LIDAR analysis and positioned at SH 77496 72493, with these values giving this hill 40.35m of drop, which is sufficient for this hill to be included in the 100m Twmpau.

 

Gathering data at the summit of Maes Glas Mawr

Gathering data at the summit of Clytiau Poethion

The full details for the hill are:

Group:  Carneddau

Name:  Clytiau Poethion

OS 1:50,000 map:  115

Summit Height:  109.1m (converted to OSGM15)

Summit Grid Reference:  SH 76337 71799

Bwlch Height:  68.7m (LIDAR)

Bwlch Grid Reference:  SH 77496 72493 (LIDAR)

Drop:  40.35m (LIDAR)

For details on the summit survey of this hill

Myrddyn Phillips (March 2019)

Mapping Mountains – Hill Reclassifications – 100m Twmpau

Goetre Coed (ST 091 965) – 100m Twmpau addition

There has been an addition of a hill to the listing of 100m Twmpau, with the summit height and its location, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Goetre Coed (ST 091 965)

The criteria for the list that this addition 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 summit of this hill is situated is Goetre Coed, 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 Fforest Fawr group of hills, which are situated in the northern part of South Wales (Region C, Sub-Region C2), and it is almost encircled by the Afon Taf (River Taff) with only its south-western side free from the river, and is positioned with the A470 road to its south-west and the A4054 road to its north-east, and has the small town of Treharris to its north-east.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in either the main P30 list or the accompanying Hills to be surveyed sub list as it was thought not to have sufficient drop to be a listed as a P30 and it was also thought not to meet the criteria then used for the sub-list.

When this list was standardised and interpolated heights and drop values also included, the details for the hill were re-assessed, but as the bwlch of the hill has a rail and road cutting the contours are not continuous on the Ordnance Survey 1:25,000 Explorer map, therefore its drop value was difficult to estimate and it remained unlisted.

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

The details for this hill were next re-assessed when the 5m contouring on OSMaps became available online, and as this mapping had continuous contours on the area of this hill’s bwlch an estimated c 40m drop value could be given to the hill, based on its 166m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 128m based on interpolation of 5m contouring between 125m – 130m.

Extract from OSMaps

However, it was not until LIDAR became available and analysed 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 Goetre Coed

The summit height produced by LIDAR analysis is 165.9m and is positioned at ST 09189 96517, and the bwlch height is 125.8m and is positioned at ST 09052 96269, with these values giving this hill 40.2m of drop which is sufficient for its inclusion to 100m Twmpau status.

The full details for the hill are:

Group:  Fforest Fawr

Name:  Goetre Coed

OS 1:50,000 map:  171

Summit Height:  165.9m (LIDAR)

Summit Grid Reference:  ST 09189 96517 (LIDAR)

Bwlch Height:  125.8m (LIDAR)

Bwlch Grid Reference:  ST 09052 96269 (LIDAR)

Drop:  40.2m (LIDAR)

Myrddyn Phillips (March 2019)

Mapping Mountains – Significant Name Changes – 100m Twmpau and Y Trechol – The Dominant Hills of Wales

Clytiau Poethion (SH 763 717)

There has been a Significant Name Change to a hill that is now listed in the 100m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height and its location, the drop and status of the hill confirmed by LIDAR analysis and its summit height subsequently confirmed by a Trimble GeoXH 6000 survey, both conducted by Myrddyn Phillips, with the latter taking place on the 10^th October 2018.

LIDAR image of Clytiau Poethion (SH 763 717)

The criteria for the two lists 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.

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

The hill is adjoined to the Carneddau group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is encircled by minor roads with the B5106 and the Afon Conwy (River Conwy) to its east, and has the town of Conwy to its north.

The hill has not previously been listed as its adjacent northerly hill of Maes Glas Mawr (SH 76876 72414) was thought to be higher, LIDAR analysis and the survey with the Trimble GeoXH 6000 proved otherwise and therefore Clytiau Poethion is now listed as the 100m Twmpau and the Lesser Dominant hill.

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 195 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 Clylliau [sic] Poethion in the apportionments, with the details on the Tithe map appearing in the parish of Caerhun and in the county named as Caernarvonshire [sic].

Extract from the apportionments

Therefore, the name this hill is now listed by in the 100m Twmpau and Y Trechol – The Dominant Hills of Wales is Clytiau Poethion, and this name was derived from the Tithe map.

The full details for the hill are:

Group:  Carneddau

Name:  Clytiau Poethion

Previously Listed Name:  not previously listed 

OS 1:50,000 map:  115

Summit Height:  109.1m (converted to OSGM15)

Summit Grid Reference:  SH 76337 71799

Bwlch Height:  68.7m (LIDAR)

Bwlch Grid Reference:  SH 77496 72493 (LIDAR)

 

Drop:  40.35m (Trimble summit and LIDAR bwlch)

Dominance:  37.00% (Trimble summit and LIDAR bwlch)

For details of the summit survey of this hill

Myrddyn Phillips (March 2019)

Mapping Mountains – Summit Relocations – The Fours - The 400m Hills of England

AS LATEST LIDAR ANALYSIS GIVES WOOD BARROW AS HIGHER THAN CHAPMAN BARROWS THE QUALIFYING HILL IS NOW LISTED AS WOOD BARROW (SS 716 425)

Chapman Barrows (SS 700 434)

There has been a Summit Relocation to a hill that is listed in the The Fours – The 400m Hills of England, with the summit height, col height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Aled Williams. 

LIDAR image of Chapman Barrows (SS 700 434) and Wood Barrow (SS 716 425)

The criteria for the list that this summit relocation applies to are:

The Fours – The 400m Hills of England.  English hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are three categories of sub hills, with this hill being included in the 400m Sub-Four category, the criteria for which are all English hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and the 2^nd edition of the booklet containing this list was published by Mapping Mountains Publications on the 24^th April 2018.

The Fours - The 400m Hills of England by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Chapman Barrows, and it is adjoined to the Dunkery Beacon group of hills, which are situated in the counties of Somerset and Devon, and it is positioned with the A39 road to its north-west and the B3358 road to its south, and has the small community of Parracombe towards the west north-west.

When the 1^st edition of the The Fours was published by Europeaklist in December 2013, the qualifying 400m Sub-Four hill was listed as Wood Barrow (SS 716 425) with 22m of drop, based on the 480m summit spot height that appears on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and a 458m col height, based on the spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map, with an accompanying note stating:

Although Chapman Barrows at SS 700 434 has a 480m map height, it is not listed as a twin Sub-Four as its 480.093m flush bracket height means ground at the base of the trig pillar will be below 480m.

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

However, it was not until LIDAR became available that the details for the summit of 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 Chapman Barrows (SS 700 434)

The height produced by LIDAR analysis to the high point of Chapman Barrows is 479.8m positioned at SS 70003 43472 and to the high point of Wood Barrow is 479.7m positioned at SS 71627 42506, and this comes within the parameters of the Summit Relocations used within this page heading, these parameters are: 

The term Summit Relocations applies to when the high point is positioned in a different field, to a different feature such as a conifer plantation, within a different map contour, a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is considered a relatively recent man-made construct, 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.

Therefore, the summit height produced by LIDAR analysis is 479.8m and this is positioned at SS 70003 43472.  This position is adjacent to where the 480m spot height appears on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and is approximately 1.8km north-westward from the high point of Wood Barrow.

The full details for the hill are:

Group:  Dunkery Beacon

Name:  Chapman Barrows

OS 1:50,000 map:  180

Summit Height:  479.8m (LIDAR)

Summit Grid Reference (New Position):  SS 70003 43472 (LIDAR) 

 

Col Height:  457.4m (LIDAR)

Col Grid Reference:  SS 72610 42583 (LIDAR)

Drop:  22.4m (LIDAR)

Myrddyn Phillips and Aled Williams (March 2019)

Mapping Mountains – Trimble Surveys – Mynydd Twr

22.10.18  Plas Gwyn (SH 524 817)  

Plas Gwyn (SH 524 817)

This hill is perched above the eastern coastline of Ynys Môn and looks out over Traeth Coch (Red Wharf Bay) and across to the forested summit of Mynydd Llwydiarth and the limestone encrusted summit of Bwrdd Arthur.  Prior to my visit I had analysed its summit and bwlch with LIDAR and now wanted an on-site visit to bag its summit and take two data sets; one from where LIDAR gives its high point to be situated and the other at a fence junction where the summit is reported to be situated on the Hill Bagging website.

I parked opposite a public football beside the A 5015 as it makes its way between Pentraeth and Benllech.  After spending the morning and early afternoon visiting four P30s dotted across the south-eastern part of the island, many of which were tucked away with the nearest access being narrow country lanes, it felt unusual to encounter fast moving traffic seemingly hurtling past going who knows where.  After waiting for a number of cars and lorries to pass I made my way over the strip of tarmac and through a kissing gate to instant tranquillity and other worldliness as an enclosed old green lane made its way south-eastward up the lower southern part of this hill.

As height was gained a gate gave access to the manicured grazing field on my left, this stretched out toward the high point of the hill, and with beautiful afternoon blue sky above and a slight warmth, and with no one about, it seemed I had the hill to myself, even sheep were absent.

I followed a boundary fence until a gap gave access to the large field toward where the high point of the hill is situated.  Approaching from the south gave me chance to examine the lay of land as I neared the summit and to me it was relatively obvious where its high point lay, once there I compared my position against the ten figure grid reference that the Trimble gave and it matched the LIDAR summit to within one metre.

Gathering data at the summit of Plas Gwyn (SH 524 817)

Having set the Trimble up and activated it to gather data I walked over to the fence boundary where the high point has been reported to be situated.  This part of the hill rises more steeply compared to where LIDAR gives the summit to be placed.  I spent a number of minutes examining this part of land and decided that a second data set was necessary.

The Trimble set-up position at the summit of Plas Gwyn (SH 524 817)

Once the Trimble had gathered and stored data from the LIDAR summit I set it up on what I judged to be the highest natural land beside the fence and again waited for the allotted data to be gathered.  During this I again examined this part of land and realised that the Trimble was placed on what looked like the remains of an old boundary that is slightly raised, but this is not shown as such on the Tithe map.

Gathering data at the second Trimble set-up position

It was a delight to wait for these two data sets to be collected as the weather was blissful with wisps of high cloud accentuating the blueness of sky.  Once the Trimble was packed away I wandered back down the hill to another gate giving access on to the public footpath and then continued on it toward the Porthllongdy Caravan Site where I met David Bennet.  David didn’t know the name of the hill or the field name where its summit is situated, but said if anyone knew it would be Michael Buckley who owns this land.

David directed me to Rhiwlas; Michael Buckley’s home, where I knocked on several doors, unfortunately no one was in, but I did meet the hedge cutter who kindly gave me a forwarding telephone number to make further enquiries.  Once contacted, Michael gave me the name of Plas Gwyn for the hill, with it taking its name from the farm to its south.        

Survey Result:

Plas Gwyn (significant name change)  

Summit Height:  76.1m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 52494 81743 (Trimble GeoXH 6000) (summit relocation confirmed)

Bwlch Height:  41.9m (LIDAR)

Bwlch Grid Reference:  SH 52209 81404 (LIDAR)

Drop:  34.2m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  44.91% (Trimble GeoXH 6000 summit and LIDAR bwlch)

For further details please consult the Trimble Survey Spreadsheet

Mapping Mountains – Hill Reclassifications – 100m Twmpau

Maes Glas Mawr (SH 768 724) – 100m Twmpau reclassified to 100m Sub-Twmpau

There has been a reclassification to a hill that is listed in the 100m Twmpau, with the summit height, its location, the drop and status of the hill confirmed by LIDAR analysis, and a subsequent summit survey with the Trimble GeoXH 6000, both conducted by Myrddyn Phillips with the latter taking place on the 10^th October 2018.

Maes Glas Mawr (SH 768 724)

The criteria for the list that this reclassification 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 summit of this hill is situated is Maes Glas Mawr, and this was derived from local enquiry and it is the name that this hill is now listed by, and it is adjoined to the Carneddau group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is encircled by minor roads with the B5106 road and the Afon Conwy (River Conwy) to its east, and has the town of Conwy towards its north.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was included in the main P30 list as its summit was thought to be higher than its adjacent and southerly hill known as Clytiau Poethion which is positioned at SH 76337 71799, both hills have now been surveyed with Clytiau Poethion confirmed as the higher resulting in the reclassification of Maes Glas Mawr.

When this list was standardised and interpolated heights and drop values also included Maes Glas Mawr was listed with an estimated c 39m of drop based on the 107m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger map and an estimated bwlch height of c 68m based on interpolation of 10m bwlch contouring between 60m – 70m.

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

These values were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and entitled the Interactive Coverage Map became available online, and the listed drop value remained the same.

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 image of Maes Glas Mawr

Importantly LIDAR analysis gave Clytiau Poethion (SH 76337 71799) as higher than Maes Glas Mawr and this has subsequently been confirmed by a Trimble GeoXH 6000 survey, therefore the bylchau for each hill is swapped as are their classifications, resulting in a Trimble GeoXH 6000 summit height for Maes Glas Mawr of 108.5m positioned at SH 76876 72414, and a bwlch height of 87.05m produced by LIDAR analysis and positioned at SH 76604 71933, with these values giving this hill 21.4m of drop, which is sufficient for this hill to be reclassified to 100m Sub-Twmpau status.

The full details for the hill are:

Group:  Carneddau

Name:  Maes Glas Mawr

OS 1:50,000 map:  115

Summit Height:  108.5m (converted to OSGM15)

Summit Grid Reference:  SH 76876 72414

Bwlch Height:  87.05m (LIDAR)

Bwlch Grid Reference:  SH 76604 71933 (LIDAR)

Drop:  21.4m (LIDAR)

For details on the summit survey of this hill

Myrddyn Phillips (March 2019)