Sunday, 26 March 2017

Mapping Mountains – Trimble Surveys – Beacon Hill


09.03.17  Cefn Nedd (SO 185 965)

Cefn Nedd (SO 185 965)

Cefn Nedd forms a neat triangle of land enclosed by minor roads above and to the south-east of the Afon Hafren (River Severn).  The name of Cefn Nedd is more strictly applicable to the uppermost enclosed field where the summit of the hill is situated, with the name deriving from the Tithe map, whilst the name usually given this hill in listings; Goron Ddu, is confirmed from local enquiry to be applicable to the lower slopes of the hill that overlook the Afon Hafren, this is where the name appears on the current Ordnance Survey 1:50,000 Landranger map.

As I parked my car on the side of the road next to the field enclosing the area of the bwlch, a farm vehicle approached, I flagged it down and talked with a local farmer for ten minutes or so, he confirmed where the name of Goron Ddu applied to, and had no objection to me taking a series of data sets in the fields next to the minor road close to the outskirts of Llandyssil.

The first data set I took was close to where the 119m spot height appears on Ordnance Survey maps, to do so I placed the Trimble on the roof of my car and measured a 1.46m offset to the road.  Over the next 90 minutes I took a further five data sets from the area of the bwlch, with the majority of these on the broad valley to valley traverse.  During this process the land remained quiet with just an occasion passing car and a distant farm vehicle chugging up a country lane breaking the silence.

The first data set at the bwlch

The third data set at the bwlch with the village of Llandyssil in the background

The fourth data set at the bwlch

The sixth data set at the bwlch

Packing the Trimble away I walked back toward the car happy in the knowledge that I judged most if not all eventualities for the position of this hill’s critical bwlch had been surveyed. 

As the weather was proving glorious with thick blue skies above and warmth cascading the land, I dispensed with my fleece.  It was a day to savour with the heralding of spring and new growth showing green in hedgerows.

I drove up the lane toward the summit of Cefn Nedd and parked beside the entrance to Coed y Wig.  An old green lane heads toward the hill from here and I followed it to two gates which give access to the upper field.

I passed this beautifully sculptured tree on the ascent of Cefn Nedd

The summit of Cefn Nedd consists of closely cropped grass close to the slopes of a wooded copse, the views northward down the Severn Valley toward Cefn Digoll and the Breiddin are expansive with both floating above the plain below.

Gathering data at the summit of Cefn Nedd

The Trimble set-up position at the summit of Cefn Nedd

After five minutes of summit data were gathered I headed back to the two gates and the old green track, a farm vehicle was approaching the green lane from the field opposite and not wanting to miss an opportunity for place-name research I waved and headed toward it.  I chatted with its occupant; Alan Harding for quite some time, he also confirmed the land where Goron Ddu is situated and gave me a number of names for local hills.

Alan Harding

After thanking Alan for his time it was only a short walk back to my car, on my way down toward it my mind wandered as the greened fields shone in front, a delicate patchwork of curves smoothed with years of grazing and interspersed with bordered and stunted trees giving slight variety to the land.  It had been a good few hours in the sunshine and enthused me to get out again the next day with the Trimble.

A greened patchwork
     

Survey Result:


Cefn Nedd (significant name change)

Summit Height:  207.2m (converted to OSGM15)

Summit Grid Reference:  SO 18524 96503

Bwlch Height:  118.1m (converted to OSGM15)

Bwlch Grid Reference:  SO 19564 95699

Drop:  89.1m (non Sub-Hump status confirmed)

Dominance:  23.26% 

 




Saturday, 25 March 2017

Mapping Mountains – Hill Reclassifications – Yr Uchafion


Fowler’s Arm Chair (SO 041 794)

There has been a reclassification to the listing of Yr Uchafion instigated from analysis of LIDAR data by Aled Williams.  Yr Uchafion is the draft title for a list of the Welsh 500m P15s that takes in all hills in Wales at or above 500m that have a minimum drop of 15m, the list is a joint compilation with Aled Williams, and details relating to this list were published on the Mapping Mountains site in November 2015.

Accompanying the main Yr Uchafion list are three sub lists; 500m Sub-Uchaf, 490m Sub-Uchaf and the Double Sub-Uchaf categories, with the reclassification of this hill affecting the Double Sub-Uchaf hills, with the criteria for inclusion to this sub category being Welsh hills at or above 490m and below 500m in height that have 14m or more and below 15m of drop.

Prior to analysis of LIDAR data by Aled the hill was listed with c 14m of drop based on an estimated summit height of c 491m and the 477m bwlch spot height that appears on the Ordnance Survey enlarged mapping hosted on the Geograph website.

The hill is situated in the Pegwn Mawr group with its Cardinal Hill being Brondre Fawr Hill (SO 041 783) and is placed in the Region of Mid and West Wales (Region B, Sub-Region B1), and is positioned between the small communities of Bwlch y Sarnau towards the south and Llanbadarn Fynydd towards the east south-east.

The hill can be accessed on public footpaths from a number of directions; however its summit is not on open access land, so if wanting to visit its high point permission to do so should be sought.

The name of the hill is Fowler’s Arm Chair and it is the first Double Sub-Uchaf to lose its status since the Yr Uchafion list was announced in November 2015, this is due to the analysis of LIDAR data by Aled.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

Aled’s analysis of LIDAR data gives the hill the following details:


Fowler’s Arm Chair

Summit Height:  489.5m

Summit Grid Reference:  SO 04122 79426

Bwlch Height:  476.4m

Bwlch Grid Reference:  SO 04192 79062

Drop:  13.1m


Therefore, the 489.5m LIDAR data produced for the summit position at SO 04122 79426 and the 476.4m LIDAR data produced for the bwlch position at SO 04192 79062 gives this hill 13.1m of drop which along with its summit height is insufficient for it to retain its status as a Double Sub-Uchaf.

This now revises the listing of Yr Uchafion which will be updated accordingly and the hill is now deleted from the ranks of Double Sub-Uchaf, with this reclassification appearing in the appropriate Change Register.


The full details for the hill are:

Cardinal Hill:  Brondre Fawr Hill

Summit Height:  489.5m (LIDAR data)

Name:  Fowler’s Arm Chair

OS 1:50,000 map:  136, 147

Summit Grid Reference:  SO 04122 79426   

Drop:  13.1m (LIDAR data)


The reclassifications to the Double Sub-Uchaf category in Yr Uchafion / The Welsh 500m P15s reported on Mapping Mountains are ills of wales as follows:



DOUBLE SUB-UCHAF ADDITIONS




DOUBLE SUB-UCHAF DELETIONS

Fowler’s Arm Chair (SO 041 794) Double Sub-Uchaf deleted with 489.5m summit height and 13.1m drop




Myrddyn Phillips and Aled Williams (March 2017)

Friday, 24 March 2017

Mapping Mountains – Hill Reclassifications – Y Pedwarau


Cwmcynydd Bank (SO 053 724)

There has been a reclassification to the listing of Y Pedwarau with a 400m Sub-Pedwar being reclassified to Pedwar status due to analysis of LIDAR data by Aled Williams.  The 400m Sub-Pedwarau is one of five categories of sub hills that accompany the main Y Pedwarau list, with the criteria for 400m Sub-Pedwar status being all Welsh hills at or above 400m and below 500m in height with 20m or more and below 30m of drop, with the criteria for Pedwar status being all Welsh hills at or above 400m and below 500m in height with a minimum 30m of drop.

The hill is situated in the Pegwn Mawr group with its Cardinal Hill being Brondre Fawr Hill (SO 041 783) and is placed in the Region of Mid and West Wales (Region B, Sub-Region B1), and is positioned between the small communities of Bwlch y Sarnau to the north-west and Abaty Cwm Hir (Abbey Cwmhir) to the south.

The summit of the hill is situated in conifer plantation but the hill can be accessed via forestry tracks from a number of directions as these encircle the upper part of the hill.  The forestry track towards the north-east and also the south-west of the summit gives access to a forest ride that passes within a few metres and to the east of the high point of the hill.

The name of the hill is Cwmcynydd Bank (previously listed in Y Pedwarau as Pt. 444m, Cwmcynydd Bank) and prior to the analysis of LIDAR data and its subsequent listing as a Pedwar the hill had been listed as a 400m Sub-Pedwar with c 27m of drop based on the 444m spot height that appears at SO 05234 72506 on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 417m at SO 05783 72592.

As Aled was analysing other hills in the vicinity against LIDAR data, he did likewise with Cwmcynydd BankLIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

Aled’s analysis of LIDAR data gives the hill the following details:


Cwmcynydd Bank

Summit Height:  451.4m

Summit Grid Reference:  SO 05342 72437

Bwlch Height:  370.9m

Bwlch Grid Reference:  SO 04664 74187

Drop:  80.5m


The reason for the dramatic increase in drop from this hill’s previously listed c 27m to the 80.5m figure given above is that the summit height for this hill usurps that of the hill positioned at SO 06116 72668 (grid reference ascertained from Trimble), and therefore the positions of the bylchau are swapped, because of this the LIDAR data for what is now considered as the lower hill is also given, and this appears below.

Aled’s analysis of LIDAR data gives the lower hill the following details:


Cwmcynydd Bank

Summit Height: 448.2m

Summit Grid Reference:  SO 06122 72660

Bwlch Height:  416.4m  

Bwlch Grid Reference:  SO 05788 72576

Drop:  31.8m


The hill now considered the lower of the two Cwmcynydd Bank summits was previously surveyed with the Trimble GeoXH 6000, but with a standard deviation of 0.4m the data set was considered unreliable and therefore the LIDAR data is being taken for the height of this hill, with the ten figure grid reference ascertained by the Trimble being used for its summit position.  The critical bwlch for the higher of these two hills was also surveyed using the Trimble and the comparison of data sets is given below:


Trimble:  370.934m (converted to OSGM15) at SO 04667 74183

LIDAR:  370.9m at SO 04664 74187 


Therefore, the 451.4m LIDAR data produced for the summit position at SO 05342 72437 is higher than the 448.2m LIDAR data produced for the Trimble summit position at SO 06116 72668, therefore the bwlch position for each hill is swapped, and with the 370.9m LIDAR and Trimble bwlch data produced for the Trimble bwlch position at SO 04667 74183 being sufficient for this hill to be reclassified to a Pedwar with 80.5m of drop.

The full details for the two hills are:


Cardinal Hill:  Brondre Fawr Hill  

Summit Height:  451.4m (LIDAR data)  

Name:  Cwmcynydd Bank  

OS 1:50,000 map:  136, 147  

Summit Grid Reference:  SO 05342 72437  

Drop:  80.5m (LIDAR summit data and Trimble and LIDAR bwlch data)  




Cardinal Hill:  Brondre Fawr Hill 

Summit Height:  448.2m (LIDAR data)

Name:  Cwmcynydd Bank

OS 1:50,000 map:  136, 147  

Summit Grid Reference:  SO 06116 72668 (Trimble data)

Drop:  31.8m (LIDAR data)


This now brings the overall total for Y Pedwarau to 445 hills with eight additions, and ten reclassifications to 400m Sub-Pedwar status since publication of the list by Europeaklist in May 2013.  The hill will be taken out of the 400m Sub-Pedwar list and added to the Pedwar list in forthcoming publications.  The list of Pedwar hills is available from the Haroldstreet website (January 2014) with all subsequent changes available via the Mapping Mountains site, with the list also having commenced publication on Mapping Mountains on the 30.01.17.

The list of additions and reclassifications from the Pedwar list since the 1st edition of Y Pedwarau was published by Europeaklist are as follows:



PEDWAR ADDITIONS









Cwmcynydd Bank (LIDAR data) (SO 053 724) 400m Sub-Pedwar reclassified to Pedwar with 80.5m drop





PEDWAR RECLASSIFICATIONS















Myrddyn Phillips and Aled Williams (March 2017)


Wednesday, 22 March 2017

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


Moel y Penmaen (SH 338 386)

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales which has resulted in the hill being added to the Lesser Welsh Dominant list.  The criteria for inclusion in this category of sub list is those P30 hills whose prominence is 33% or more and below 50% of their absolute height.

The details relating to this hill’s inclusion as a Lesser Welsh Dominant hill are retrospective as it appeared in the Pen Llŷn group of hills when published on the Mapping Mountains site on the 11th February 2016.

The hill did not appear in the original listing of Y Trechol – The Dominant Hills of Wales even though the details on the then current Ordnance Survey maps showed a 153m summit spot height and bwlch contours between 90m – 100m, with an estimated bwlch height of c 92m giving a drop of c 61m and a Dominance of 39.87% which is sufficient for inclusion into the Lesser Welsh Dominant list.

The hill is listed in the Pen Llŷn group and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Garn Ganol (SH 364 447), and it is situated between the small communities of Boduan to the south-west and Llannor to the south-east.

If wanting to visit the hill a track to the south-east which makes its way toward a small reservoir gives easy access to the upper part of the hill which is on open access land.

The name of the hill is Moel y Penmaen and it qualifies for Lesser Welsh Dominant status based on a 153m summit and a c 92m bwlch height, with these values giving this hill c 61m of drop and 39.87% of Dominance.


The full details for the hill are:

Group:  Pen Llŷn

Name:  Moel y Penmaen

Dominance:  39.87%

OS 1:50,000 map:  123

Summit Grid Reference:  SH 33810 38687

Summit Height:  153m

Drop Summit to Bwlch:  c 61m

Drop Bwlch to ODN:  c 92m 



Myrddyn Phillips (March 2017)






Tuesday, 21 March 2017

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


Pt. c 71m (SH 310 297)

There has been an addition to the listing of Y Trechol – The Dominant Hills of Wales due to detail included on the Ordnance Survey enlarged mapping hosted on the Geograph website.  This has resulted in the hill being added to the Lesser Welsh Dominant list.  The criteria for Lesser Welsh Dominant status is those P30 hills whose prominence is 33% or more and below 50% of their absolute height.

The details relating to this hill’s inclusion as a Lesser Welsh Dominant hill are retrospective as it appeared in the Pen Llŷn group of hills when published on the Mapping Mountains site on the 11th February 2016.

Prior to this hill’s inclusion as a Lesser Welsh Dominant hill it was listed with c 25m of drop which is insufficient for consideration to this sub category of hill, with this drop value based on an estimated summit height of c 71m based on the size of the uppermost 70m ring contour on Ordnance Survey maps in comparison to the size of contours below it, and an estimated bwlch height of c 46m based on bwlch contouring between 40m – 50m that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps.   

The hill is listed in the Pen Llŷn group and is placed in the Region of North Wales (Region A, Sub-Region A1) with its Cardinal Hill being Garn Fadrun (SH 278 351), and it is situated between the small communities of Llanbedrog to the north-east, Mynytho to the north-west and Abersoch to the south.

If wanting to visit the hill permission to do so should be sought as the summit area is not a part of open access land, however the hill has a number of public footpaths encircling it that start from the A 499 road to its east and the network of minor roads to its north and west.

The hill is being listed by the point (Pt. c 71m) notation as an appropriate name either known locally or from historical research has not been found by the author, although when the hill was first included in the P30 Welsh lists that appeared on Geoff Crowder’s v-g.me website it was by an invented name of Castellmarch, this name was taken from buildings situated to the east of the summit.

It is included as a Lesser Welsh Dominant hill as the Ordnance Survey enlarged mapping hosted on the Geograph website has contours at 5m intervals giving the hill a 41m bwlch spot height with bwlch contouring between 40m – 45m, as opposed to the previously estimated bwlch height of c 46m based on the 40m – 50m bwlch contouring on the 1:25,000 Explorer map.  With an estimated c 71m summit height and a 41m bwlch height it gives this hill c 30m of drop which is sufficient for consideration to the Dominant list, and as these values give this hill 42.25% Dominance it is now listed as a Lesser Welsh Dominant hill.


The full details for the hill are:

Group:  Pen Llŷn

Name:  Pt. c 71m

Dominance:  42.25%

OS 1:50,000 map:  123

Summit Grid Reference:  SH 31034 29730

Summit Height:  c 71m

Drop Summit to Bwlch:  c 30m

Drop Bwlch to ODN:  41m 



Myrddyn Phillips (March 2017)