Mapping Mountains – Trimble Surveys – Moelwyn Mawr

 

22.09.21  Bryn y Gwynt (SH 599 449) 

LIDAR image of Bryn y Gwynt (SH 599 449)

This hill entered the ranks of P30s in 2018 due to LIDAR analysis conducted by Aled Williams and today it was time for him to visit his new hill!  However, this was not our original plan as we had hoped to visit Moel y Dyniewyd (SH 612 477) and its accompanying hills, but the weather for such a walk was not encouraging with low gloom and drizzled rain, and although the forecast gave for a brighter afternoon, we didn’t fancy the thought of heading up this hill in unfavourable conditions, getting wet in the process, with the prospect of wandering around in wild surrounds trying to pinpoint summit and bwlch positions.  Therefore, we needed a plan B and Aled quickly came up with one; visit a number of lower heighted P30s that neither of us had been to, including the relatively recent new P30 of Bryn y Gwynt. 

This hill was originally listed as Coed Hafod y Llyn in the Welsh P30 lists published on Geoff Crowder’s v-g.me website.  Its name was changed to Bryn y Gwynt due to local knowledge from Aled, with this name also appearing on the series of Ordnance Survey Six-Inch maps.  As well as reclassifying this hill to P30 status, the original LIDAR analysis also promoted Bryn y Gwynt to Dominant status. 

Extract from the Ordnance Survey series of Six-Inch maps

Our quickly re-arranged plan was perfect as a wooded hill would give us shelter from the drizzled rain that still fell as we got our boots on, having parked just off the A4085 road on a track that runs parallel with the train line. 

As we set off the hill loomed above us, with its whole upper section covered in deciduous trees, which on many an occasion can be a delight to walk through.  However, on other occasions deciduous woods can be hellish with no semblance of a path, with going tough through all manner of undergrowth with brambles being the main obstacle.  This hill had a bit of both, but in the main it was a lovely place to walk in. 

Aled leading the way up Bryn y Gwynt

Aled navigated us upward over rich greened rising slopes through mature woodland with plenty of space between trees and occasional rocks interspersed amongst the greenery.  It was a wonderful place to be on such a morning, but with the added bonus of autumnal colour that in a few weeks will adorn this hill, it must be a sheer delight to then visit. 

Without the aid of ten figure grid references for this and the next two summits we visited, each walk was dependent upon finding our own way to the high point, which for me today required contentedly following Aled, who made good steady progress up the hill.  However, this was still an unusual experience for me, as for each walk and survey I usually come prepared with a mass of noted detail, including summit feature and all necessary ten figure grid references for both summit and adjoining bwlch. 

We reached a point that looked to be the summit; I took a few photographs and started to assess the rock that Aled was now standing on for Trimble placement.  Before setting the equipment up we decided to continue in to the wood as ground farther on looked as if it was higher, and so it proved and significantly so. 

The second point we reached was definitely the summit and soon the Trimble was set up atop my rucksack, with the measurement offset noted between its internal antenna and the ground at its base and it was soon quietly beeping away collecting individual datum points. 

Gathering data at the summit of Bryn y Gwynt

Once allotted data were gathered and stored, I closed the equipment down, took a few photographs and packed it away.  We now reversed our inward route avoiding all steep drops and soon found ourselves back on the track with Aled’s car about 100 metres away.  One wooded hill visited and two more to go. 

 

Survey Result: 

 

Bryn y Gwynt (significant name change)

Summit Height:  59.9m (converted to OSGM15, Trimble GeoXH 6000) (significant height revision)

Summit Grid Reference:  SH 59949 44919 (summit relocation confirmed)

Bwlch Height:  28.0m (LIDAR)

Bwlch Grid Reference:  SH 60224 45248 & SH 60226 45258 & SH 60227 45259 (LIDAR)

Drop:  31.9m (30-99m Twmpau addition) (30-99m Sub-Twmpau reclassified to 30-99m Twmpau)

Dominance:  53.21% (Dominant addition)

 

 

For further details please consult the Trimble Survey Spreadsheet

 

 

 

 

Mapping Mountains – Summit Relocations – 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales

Bryn y Gwynt (SH 599 449)

There has been a Summit Relocation to a hill that is now listed in the 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height, their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Aled Williams and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and Aled Williams.

LIDAR image of Bryn y Gwynt (SH 599 449)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 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.

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, with the Introduction to the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format.

The name the hill is listed by is Bryn y Gwynt and this was derived from local enquiry and the series of Ordnance Survey Six-Inch maps and it is situated in the Moelwynion range of hills in the Region of North Wales (Region A, Sub-Region A1), and is positioned with the A 4085 road to its north-east and has the Welsh Highland Railway to its immediate west and overlooks the Afon Glaslyn also to its west, and has the village of Beddgelert to its north north-west and the town of Porthmadog to its south south-west.

The hill is a part of Coed Hafod y Llyn, and as this name implies its summit is placed in woodland which is deciduous, and as the summit is not a part of designated open access land permission to visit should be sought, however paths are indicated on the map to the north, east and south of this hill’s summit and therefore gaining access to its lower slopes has probably been accepted for many years.

Prior to LIDAR analysis this hill was listed in the Hills to be surveyed sub list that accompanied the Welsh P30 lists published on Geoff Crowder’s v-g.me website.  When these sub lists were standardised and also drop values added, this hill was listed with an estimated c 29m of drop based on the 56m spot height that appears on the Ordnance Survey 1:25,000 Explorer map at SH 59881 44828 and an estimated bwlch height of c 27m based on contouring at 10m intervals between 20m – 30m, with the caveat that the 27m spot height that appears on a road at SH 60168 45293 on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website is judged not to be positioned at the critical bwlch.

Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website

LIDAR analysis confirms this hill to be a 30-99m Twmpau and a Dominant hill, but as the summit has now been surveyed with the Trimble GeoXH 6000, it is this result that is being prioritised for listing purposes.

The Trimble GeoXH 6000 gathering data at the summit of Bryn y Gwynt

Therefore, the summit height produced by the Trimble GeoXH 6000 survey is 59.9m and this is positioned at SH 59949 44919, this position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and is approximately 80 metres north-eastward from where the previously listed summit position.

The full details for the hill are:

Group:  Moelwynion

Name:  Bryn y Gwynt

OS 1:50,000 map:  124

Summit Height:  59.9m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference (New Position):  SH 59949 44919 (Trimble GeoXH 6000) 

  

Bwlch Height:  28.0m (LIDAR)

Bwlch Grid Reference:  SH 60224 45248 & SH 60226 45258 & SH 60227 45259 (LIDAR)

Drop:  31.9m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  53.21% (Trimble GeoXH 6000 summit and LIDAR bwlch)  

My thanks to Aled Williams for sending the details of this hill to me.

Myrddyn Phillips (February 2018)

Mapping Mountains – Significant Height Revisions – 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales

Bryn y Gwynt (SH 599 449)

There has been a Significant Height Revision to a hill that is now listed in the 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height, their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Aled Williams and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and Aled Williams.

LIDAR image of Bryn y Gwynt (SH 599 449)

The criteria for the two listings that this significant height revision applies to are:

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 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.

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, with the Introduction to the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format.

The name the hill is listed by is Bryn y Gwynt and this was derived from local enquiry and the series of Ordnance Survey Six-Inch maps and it is situated in the Moelwynion range of hills in the Region of North Wales (Region A, Sub-Region A1), and is positioned with the A 4085 road to its north-east and has the Welsh Highland Railway to its immediate west and overlooks the Afon Glaslyn also to its west, and has the village of Beddgelert to its north north-west and the town of Porthmadog to its south south-west.

The hill is a part of Coed Hafod y Llyn, and as this name implies its summit is placed in woodland which is deciduous, and as the summit is not a part of designated open access land permission to visit should be sought, however paths are indicated on the map to the north, east and south of this hill’s summit and therefore gaining access to its lower slopes has probably been accepted for many years.

Prior to LIDAR analysis this hill was listed in the Hills to be surveyed sub list that accompanied the Welsh P30 lists published on Geoff Crowder’s v-g.me website.  When these sub lists were standardised and also drop values added, this hill was listed with an estimated c 29m of drop based on the 56m spot height that appears on the Ordnance Survey 1:25,000 Explorer map at SH 59881 44828 and an estimated bwlch height of c 27m based on contouring at 10m intervals between 20m – 30m, with the caveat that the 27m spot height that appears on a road at SH 60168 45293 on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website is judged not to be positioned at the critical bwlch.

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

The summit height produced by LIDAR analysis is 58.4m and is positioned at SH 59949 44915, but as the summit has now been surveyed with the Trimble GeoXH 6000 giving 59.9m positioned at SH 59949 44919, it is this result that is being prioritised for listing purposes.  This is not a dramatic height revision when 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 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.  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 revisions.

The Trimble GeoXH 6000 gathering data at the summit of Bryn y Gwynt

Therefore, the new listed summit height of this hill is 59.9m and this was derived from a Trimble GeoXH 6000 survey, this is 3.9m higher than its previously listed height of 56m which appears as a spot height on the Ordnance Survey 1:25,000 Explorer map.

The full details for the hill are:

Group:  Moelwynion

Name:  Bryn y Gwynt

OS 1:50,000 map:  124

Summit Height (New Height):  59.9m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 59949 44919 (Trimble GeoXH 6000) 

  

Bwlch Height:  28.0m (LIDAR)

Bwlch Grid Reference:  SH 60224 45248 & SH 60226 45258 & SH 60227 45259 (LIDAR)

Drop:  31.9m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  53.21% (Trimble GeoXH 6000 summit and LIDAR bwlch)  

My thanks to Aled Williams for sending the details of this hill to me.

Myrddyn Phillips (February 2018)

Mapping Mountains – Significant Name Changes – 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales

Bryn y Gwynt (SH 599 449)

There has been a Significant Name Change to a hill that is now listed in the 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height, their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Aled Williams and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and Aled Williams.

Bryn y Gwynt (SH 599 449)

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

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 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.

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, with the Introduction to the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format.

The hill is situated in the Moelwynion range of hills in the Region of North Wales (Region A, Sub-Region A1), and is positioned with the A 4085 road to its north-east and has the Welsh Highland Railway to its immediate west and overlooks the Afon Glaslyn also to its west, and has the village of Beddgelert to its north north-west and the town of Porthmadog to its south south-west.

The hill appeared in the Hills to be surveyed sub list that accompanied the main Welsh P30 lists that were published on Geoff Crowder’s v-g.me website under the name of Coed Hafod-y-llyn.  This is the name of the wood where the hill is situated and would be an appropriate name to use if a name for the hill itself did not exist.

Coed Hafod-y-llyn

56m

SH598448

124

18

Hill list authors are prone to list a hill by the name that appears nearest to its summit on contemporary Ordnance Survey maps, without much consideration for its local or historical confirmation, or whether map placement is appropriate, or as in this case whether an individual name for the hill in preference to the name of the wood it is situated in, exists.  This is not a practice I now advocate as with time and inclination place-name date can be improved by asking local people or by examining historical documents, through this form of research an appropriate name for the hill can usually be found, and in the case of this hill it was local knowledge from Aled Williams coupled with historical information from the Ordnance Survey series of Six-Inch maps that gave the name of Bryn y Gwynt for this hill.  

Extract from the series of Ordnance Survey Six-Inch maps

Therefore, the name this hill is now listed by in the 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales is Bryn y Gwynt and this was derived from local enquiry and the Ordnance Survey series of Six-Inch maps.

The full details for the hill are:

Group:  Moelwynion

Name:  Bryn y Gwynt

Previously Listed Name:  Coed Hafod-y-llyn

Summit Height:  59.9m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 59949 44919 (Trimble GeoXH 6000) 

  

Bwlch Height:  28.0m (LIDAR)

Bwlch Grid Reference:  SH 60224 45248 & SH 60226 45258 & SH 60227 45259 (LIDAR)

Drop:  31.9m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  53.21% (Trimble GeoXH 6000 summit and LIDAR bwlch)  

My thanks to Aled Williams for sending the details of this hill to me.

Myrddyn Phillips (February 2018)

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

Bryn y Gwynt (SH 599 449) – Dominant addition

There has been an addition to a hill that is now listed in the Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height, their locations, the drop, dominance and status of the hill confirmed by LIDAR analysis conducted by Aled Williams and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and Aled Williams.

LIDAR image of Bryn y Gwynt (SH 599 449)

The criteria for the list that this addition applies to are:

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, with the Introduction to the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format.

The name the hill is listed by is Bryn y Gwynt and this was derived from local enquiry and the series of Ordnance Survey Six-Inch maps and it is situated in the Moelwynion range of hills in the Region of North Wales (Region A, Sub-Region A1), and is positioned with the A 4085 road to its north-east and has the Welsh Highland Railway to its immediate west and overlooks the Afon Glaslyn also to its west, and has the village of Beddgelert to its north north-west and the town of Porthmadog to its south south-west.

The hill is a part of Coed Hafod y Llyn, and as this name implies its summit is placed in woodland which is deciduous, and as the summit of the hill is not a part of designated open access land permission to visit should be sought, however paths are indicated on the map to the north, east and south of this hill’s summit and therefore gaining access to its lower slopes has probably been accepted for many years.

Prior to LIDAR analysis this hill was listed in the Hills to be surveyed sub list that accompanied the Welsh P30 lists published on Geoff Crowder’s v-g.me website.  When these sub lists were standardised and also drop values added, this hill was listed with an estimated c 29m of drop based on the 56m spot height that appears on the Ordnance Survey 1:25,000 Explorer map at SH 59881 44828 and an estimated bwlch height of c 27m based on contouring at 10m intervals between 20m – 30m, with the caveat that the 27m spot height that appears on a road at SH 60168 45293 on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website is judged not to be positioned at the critical bwlch.

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 analysis confirms Bryn y Gwynt to be a Dominant hill, and as the summit has now been surveyed with the Trimble GeoXH 6000, it is this result that is being prioritised for listing purposes.

The Trimble GeoXH 6000 gathering data at the summit of Bryn y Gwynt

Therefore, the addition of this hill to the Y Trechol - The Dominant Hills of Wales list is due to LIDAR analysis and a subsequent Trimble GeoXH 6000 survey, resulting in a 59.9m summit height and a 28.0m bwlch height, with these values giving this hill 31.9m of drop and 53.21% dominance, which is sufficient for it to be classified as a Dominant hill.

The full details for the hill are:

Group:  Moelwynion

Name:  Bryn y Gwynt

OS 1:50,000 map:  124

Summit Height:  59.9m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 59949 44919 (Trimble GeoXH 6000) 

  

Bwlch Height:  28.0m (LIDAR)

Bwlch Grid Reference:  SH 60224 45248 & SH 60226 45258 & SH 60227 45259 (LIDAR)

Drop:  31.9m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  53.21% (Trimble GeoXH 6000 summit and LIDAR bwlch)

My thanks to Aled Williams for sending the details of this hill to me.

Myrddyn Phillips (January 2018)

Mapping Mountains – Hill Reclassifications – 30-99m Twmpau

Bryn y Gwynt (SH 599 449) – 30-99m Sub-Twmpau reclassified to 30-99m Twmpau

There has been a reclassification to a hill that is listed in the 30-99m Twmpau, with the summit height, bwlch height, their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Aled Williams and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and Aled Williams.

LIDAR image of Bryn y Gwynt (SH 599 449)

The criteria for the list that this reclassification applies to are:

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 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.

The name the hill is listed by is Bryn y Gwynt and this was derived from local enquiry and the series of Ordnance Survey Six-Inch maps and it is situated in the Moelwynion range of hills in the Region of North Wales (Region A, Sub-Region A1), and is positioned with the A 4085 road to its north-east and has the Welsh Highland Railway to its immediate west and overlooks the Afon Glaslyn also to its west, and has the village of Beddgelert to its north north-west and the town of Porthmadog to its south south-west.

The hill is a part of Coed Hafod y Llyn, and as this name implies its summit is placed in woodland which is deciduous, and as the summit of the hill is not a part of designated open access land permission to visit should be sought, however paths are indicated on the map to the north, east and south of this hill’s summit and therefore gaining access to its lower slopes has probably been accepted for many years.

Prior to LIDAR analysis this hill was listed in the Hills to be surveyed sub list that accompanied the Welsh P30 lists published on Geoff Crowder’s v-g.me website.  When these sub lists were standardised and also drop values added, this hill was listed with an estimated c 29m of drop based on the 56m spot height that appears on the Ordnance Survey 1:25,000 Explorer map at SH 59881 44828 and an estimated bwlch height of c 27m based on contouring at 10m intervals between 20m – 30m, with the caveat that the 27m spot height that appears on a road at SH 60168 45293 on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website is judged not to be positioned at the critical bwlch.

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 analysis confirms this hill to be a 30-99m Twmpau, and as the summit has now been surveyed with the Trimble GeoXH 6000, it is this result that is being prioritised for listing purposes.

The Trimble GeoXH 6000 gathering data at the summit of Bryn y Gwynt

Therefore, the reclassification of this hill from 30-99m Sub-Twmpau status is due to LIDAR analysis and a subsequent Trimble GeoXH 6000 survey, resulting in a 59.9m summit height and a 28.0m bwlch height, with these values giving this hill 31.9m of drop, which is sufficient for it to be classified as a 30-99m Twmpau.

The full details for the hill are:

Group:  Moelwynion

Name:  Bryn y Gwynt

OS 1:50,000 map:  124

Summit Height:  59.9m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 59949 44919 (Trimble GeoXH 6000) 

  

Bwlch Height:  28.0m (LIDAR)

Bwlch Grid Reference:  SH 60224 45248 & SH 60226 45258 & SH 60227 45259 (LIDAR)

Drop:  31.9m (Trimble GeoXH 6000 summit and LIDAR bwlch)

My thanks to Aled Williams for sending the details of this hill to me.

Myrddyn Phillips (January 2018)