Mapping Mountains – Trimble Surveys – Moel y Gamelin

 

27.01.24  Caer Drewyn (SJ 091 444) 

Caer Drewyn (SJ 091 444)

The high point of Caer Drewyn is listed as a Subhump and Trichant.  This would be enough to encourage many a hill bagger to visit, but it is the remains of the Iron Age hill fort that is the main attraction.  The stone walled construction is perfectly placed overlooking two river valleys, with the Afon Dyfrdwy (River Dee) to its south and a tributary to its west.

Cofein reports that the hill fort had three phases of construction, with the initial part surviving as an earthwork to the north-east of the main construction and which is evident close to the high point of the hill, which is known locally after its main feature of the ancient hill fort; Caer Drewyn. 

Mosaic of Caer Drewyn outside the leisure centre in Corwen

The summit of this hill had previously been surveyed by John Barnard and Graham Jackson and it was this that was our objective for the day, that and a meal and catch up and a few hours spent in good company.  We met in Y Bala and wandered in to town for a hearty breakfast in Hoffi Coffi.  After an hour or so of nourishment and conversation we took two cars north-eastward to Corwen and parked on the northern side of the river in the leisure centre car park.  This would enable Mark to head directly back to Mold after the walk and for Aled to drive back to Y Bala where my car had been left, before he continued to Porthmadog and I headed home to Welshpool.

Making our way up the muddied narrow lane

From the convenience of the car park it’s not a great distance to the top of Caer Drewyn, however it is steep and especially so if opting for the direct path, which we followed.  But before the steep part we leisurely walked past the entrance to the leisure centre with me setting a comfortable slow plod at the back, before venturing a short distance up the B5437 road which was closed to traffic beyond its intersection with the bridge that crosses the river to the centre of Corwen.  Beyond the intersection we took the first left and headed up a muddied narrow lane to where a public footpath sign indicated the start of the steep uphill. 

The view south-west during the ascent of Caer Drewyn

Thankfully with a few stops to regain breath and enjoy the ever expanding view the steep bit was not too taxing.  This brought us over a green lane which we used as our descent route before continuing up to the remains of the walled enclosure.  The view extended toward Aran Fawddwy and the pyramidal coned summit profile of Arenig Fawr, and although conditions were overcast both were clear of cloud.  Sadly the sun did not give colour to the land until we arrived back at the cars, but this did not detract from the views, however just a little flash of sunlight can add so much to an overcast day and especially so at this time of year, when the land can become illuminated with the slightest direct sunlight. 

Mark and Aled making their way up the ancient embankment

As Mark and Aled followed a path on the ancient embankment, I kept to another path just below, with each joining near the top of the main walled enclosure.  The high point of the hill was just beyond with a slight descent to a gate and then a manicured green field leading to the summit of the hill. 

The field leading to the summit of Caer Drewyn

The high point of Caer Drewyn consists of a small mound with embedded rock.  I soon had the Trimble aligned with its high point and quickly measured the offset between its internal antenna and the ground at its base, and when the 0.1m accuracy level appeared on the screen I pressed Log and walked away so as not to disturb satellite reception. 

The Trimble GeoXH 6000 gathering data at the summit of Caer Drewyn

Once the equipment had done its stuff and was packed away, only the descent remained, which for me now meant I could at least talk, with much of the uphill consisting of a huff and a puff.  Reversing our inward route to the gate we then followed the green track as it gently lost height and zig zagged around the hill regaining our inward route at the muddied narrow lane.  It proved an ideal hill to visit for this time of year and two hours after setting off we were back at the awaiting cars. 

 

Survey Result:

 

Caer Drewyn (significant name change)         

Summit Height:  313.5m (converted to OSGM15, Leica GS15)

Summit Grid Reference:  SJ 09127 44416 (Leica GS15)

Bwlch Height:  222.7m (LIDAR)

Bwlch Grid Reference:  SJ 09770 45600 (LIDAR)

Drop:  90.8m (Leica GS15 summit and LIDAR bwlch) (Trichant addition)

Dominance:  28.96% (Leica GS15 summit and LIDAR bwlch)

 

 

For further details please consult the Trimble Survey Spreadsheet

 

 

Mapping Mountains – Significant Name Changes – Y Trichant – The 300m Hills of Wales

 

Caer Drewyn (SJ 091 444) 

There has been a Significant Name Change to a hill that is listed in the Y Trichant – The 300m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips, with a subsequent Leica GS15 survey conducted by John Barnard and Graham Jackson. 

Caer Drewyn (SJ 091 444)

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

Y Trichant – The 300m Hills of Wales.  Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13^th May 2017. 

Y Trichant - The 300m Hills of Wales by Myrddyn Phillips

The hill is adjoined to the Moel y Gamelin group of hills, which are situated in the north-eastern part of North Wales (Region A, Sub-Region A2), and it is positioned with the A5104 road to its north, the B5437 road to its south and the B5436 road to its east, and has the village of Carrog towards the east south-east. 

The qualifying hill appeared in the original 300m height band of Welsh P30 hills on Geoff Crowder’s v-g.me website under the transposed and invented name of Pen Coed Mawr, with an accompanying note stating; Name from wood to the South, and it was included in the main P30 list and given twin topped 314m map heighted summit status along with its adjacent hill positioned at SJ 094 443.

Pen Coed Mawr

314m

SJ091444

125

255/256

Name from wood to the South.

 

After the P30 lists were standardised and interpolated heights and drop values also included, this hill was listed as the non-priority summit with 18m of drop based on the 314m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 296m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map, with its adjacent 314m twin summit given priority status and listed with an estimated c 91m of drop based on the 314m summit spot height and an estimated c 223m bwlch height based on interpolation of 10m contouring between 220m – 230m that appear on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.  Subsequent LIDAR analysis gives the summit positioned at SJ 09438 44364 as slightly lower and therefore it loses priority twin top status and the bylchau are swapped. 

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

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 transpose the name of a near wood and prefix it with the word Pen.  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. 

Prior to local enquiry information being passed to me, and 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 661 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 Ffridd y Gaer, with the details on the Tithe map appearing in the parish of Corwen and in the county named as Merioneth. 

Extract from the apportionments

However, as the locally known name for this hill compliments its main named feature this is being prioritised for its listed name, and this information was passed on to me by Aled Williams.

Therefore, the name this hill is now listed by in the Y Trichant – The 300m Hills of Wales is Caer Drewyn, and this was derived from local enquiry. 

 

The full details for the hill are: 

Group:  Moel y Gamelin 

Name:  Caer Drewyn 

Previously Listed Name:  Pen Coed Mawr 

OS 1:50,000 map:  125

Summit Height:  313.5m (Leica GS15)                                                           

Summit Grid Reference:  SJ 09127 44416 (Leica GS15) 

Bwlch Height:  222.7m (LIDAR) 

Bwlch Grid Reference:  SJ 09770 45600 (LIDAR) 

Drop:  90.8m (Leica GS15 summit and LIDAR bwlch) 

 

Myrddyn Phillips (March 2021)

Mapping Mountains – Hill Reclassifications – Y Trichant – The 300m Hills of Wales

Caer Drewyn (SJ 091 444) – Trichant addition

There has been an addition to the list of Y Trichant – The 300m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips, with a subsequent Leica GS15 survey conducted by John Barnard and Graham Jackson. 

Caer Drewyn (SJ 091 444)

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

Y Trichant – The 300m Hills of Wales – Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant, with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13^th May 2017. 

Y Trichant - The 300m Hills of Wales by Myrddyn Phillips

The name the hill is now listed by is Caer Drewyn, and this was derived from local enquiry by Aled Williams, and it is adjoined to the Moel y Gamelin group of hills, which are situated in the north-eastern part of North Wales (Region A, Sub-Region A2), and it is positioned with the A5104 road to its north, the B5437 road to its south and the B5436 road to its east, and has the village of Carrog towards the east south-east. 

When the original 300m height band of Welsh P30 hills was published on Geoff Crowder’s v-g.me website, this hill was included in the main P30 list and given twin topped 314m map heighted summit status along with its adjacent hill positioned at SJ 094 443. 

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

After the P30 lists were standardised and interpolated heights and drop values also included, this hill was listed as the non-priority summit with 18m of drop based on the 314m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 296m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map, with its adjacent 314m twin summit given priority status and listed with an estimated c 91m of drop based on the 314m summit spot height and an estimated c 223m bwlch height based on interpolation of 10m contouring between 220m – 230m that appear on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

However, it was not until LIDAR became available that the details for these two summits 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 gives the following detail for each summit: 

313.0m positioned at SJ 09438 44364. 

313.1m positioned at SJ 09125 44411.

 

The summit of these two hills have now been surveyed by the Leica GS15 and it is this result that is being prioritised for this hill.

Therefore, the addition of this hill to Trichant status is due to LIDAR analysis and a subsequent Leica GS15 survey, resulting in a 313.5m summit height and a 222.7m bwlch height, with these values giving this hill 90.8m of drop, which is sufficient for it to be classified as a Trichant. 

 

The full details for the hill are: 

Group:  Moel y Gamelin 

Name:  Caer Drewyn 

OS 1:50,000 map:  125

Summit Height:  313.5m (Leica GS15)                                                           

Summit Grid Reference:  SJ 09127 44416 (Leica GS15) 

Bwlch Height:  222.7m (LIDAR) 

Bwlch Grid Reference:  SJ 09770 45600 (LIDAR) 

Drop:  90.8m (Leica GS15 summit and LIDAR bwlch) 

 

Myrddyn Phillips (March 2021)