Mapping Mountains – Trimble Surveys – Mynydd Twr

13.09.15  Ynysoedd y Moelrhoniaid (SH 267 947) and Ynys Arw (SH 266 945)   

Ynysoedd y Moelrhoniaid (SH 267 947)

The islets of Ynysoedd y Moelrhoniaid lie like a rough pearled necklace, wave battered 3 kilometres (1.9 miles) off the north-west coast of Ynys Môn.  They form a compact archipelago oriented north-east to south-west and stare back on their much larger island neighbour.  Perched on their highest point is The Skerries Lighthouse, with the word Skerry deriving from the Old Norse ‘sker,’ which means a small rocky reef or island, with the Welsh name for the islands translating as ‘the islands of Bald-headed Grey Seals’.

Our visit to these islands was organised by Adrian Rayner via Rib Ride, who are based in Holyhead and run a variety of trips around the north-west coast of Ynys Môn.  We met at Holyhead Marina and congregated in the café and waited for Adrian’s arrival.  There were 12 booked for this trip; George Morl, Alan Holmes, Alex Cameron, Douglas Law, Bob Kerr, Sarah Kerr, Tony Jenkins, Rob Woodall, Sheila Glew, John Glew, Adrian Rayner and me, also with us was Gordon Adshead who had come to see us off.

(L-R) Alex, Gordon, Adrian, John, Sheila, George, Tony, Alan, Sarah, Bob, Doug, Charles (skipper) and Rob

Charles; our skipper for the day

Once the formalities had been conducted beside the RIB we climbed aboard for a rather luxuriant passage out to sea.  The RIB used for this trip was once owned by Bear Grylls and his name and image is still used in Rib Ride’s promotional material.  The RIB was rather plush with a central cabin which had fold out canopied sides to use when the weather was rough, and an option for seated or standing position behind the controls and which was protected by a Perspex screen.  Behind this was a seat long enough for five people and in front was seating for five or six people.

At the front of the RIB

And at the back of the RIB.  Photo: RibRide

The forecast for the afternoon was good, and we had been lucky as no more than two days prior to today it was predicted that rain was going to envelop this part of the country for the whole afternoon.  As we pulled out from Holyhead the sky cast out colour and the sea was becalmed.  Beyond the harbour breakwater there was a light swell as we proceeded across the straight between Ynys Môn and Ynysoedd y Moelrhoniaid, but conditions proved relatively calm.

It’s a wonderful experience nearing an island, watching as it forever gets larger on the horizon, and today it was the islands Lighthouse that dominated the view as it stood firmly in place attached on the highest part of the archipelago with its white coloured exterior set against the backdrop of a sun drenched grey sky. 

The Skerries Lighthouse

The RIB slowly rounded the western side of the islands and was manoeuvred into the small bay below the Lighthouse.  This entrance was magical as we were suddenly transported in to a different world full of lazy seals whooping their guttural calls and an assortment of small, delightful islets, all ready for us to explore.

Seals relaxing in the afternoon sun

Once the RIB had been secured onto the iron barred ladder leading vertically up the sides of rock we clambered up and started our exploration of the islands.  It seems that there is a need to head toward the high point of any hill or island and today was no exception.  The path leading up to the Lighthouse led through a beautiful array of white daisies, all looking up with their colour mixed in their green rooted grass, set against the white of the Lighthouse they resembled a mountain meadow in spring.

Bob, followed by Alan, climbing up the ladder onto the island

Bob and Sarah with The Skerries Lighthouse in the background

The carpet of flowers

As I walked around the Lighthhouse the ground dropped steeply away to the east and the coastline of Ynys Môn gleamed back in its hazy afternoon light.  There were two potential summit points, one on the southern side of the Lighthouse and the other on the western side.  There was consensus between myself, Alan and one or two others that the highest point was on the southern side, this high point consisted of a rock that was positioned just under the base of the walkway which encircled much of the eastern and southern side of the Lighthouse, however the highest rock was pinned in with buildings either side of it, this had potential to disrupt satellite coverage, and as I set the Trimble up with its internal antenna aligned to the high point of what remains of the natural rock I thought it would take a long time for the 0.1m accuracy level to be attained before logging should start.  Remarkably this accuracy level was attained within a couple of minutes and I quickly pressed ‘Log’ and hid behind a rock, we’ll have to see what the processed data is like and whether the data set is good or has been compromised by the position of the Trimble.

Gathering data at the summit of Ynysoedd y Moelrhoniaid

Charles and Alan look on with the Trimble positioned on the highest natural rock that still exists on Ynysoedd y Moelrhoniaid

Once summit data were collected I headed to the western side of the Lighthouse wanting to gather another five minute data set from the other potential summit position, this was straight under the side of the Lighthouse and after waiting ten minutes the accuracy level was only down to 0.19m, and whilst waiting I looked out on everyone exploring the other islets, so I decided to switch the Trimble off and start doing likewise.

The Trimble positioned on the high point on the western side of the Lighthouse

The highest islet where the Lighthouse is situated has another islet to its south-west named Ynys Arw; this has two main high points, with the southerly of these being the highest.  There were already a number of people scampering all over these high points and I headed over to join them.  This south-westerly islet is cut off from the others at high tide but the pebbles and seaweed of relatively dry land had been exposed as low tide enabled us to visit farther afield from the main islet.

Sarah, Alex and Rob (on left of photo) on the adjacent high point to the Lighthouse with the summit of Ynys Arw on the right of photo

Alex and Rob heading over to Ynys Arw

Sarah below the Lighthouse, with its lower rocks on the right of this photo

John helped me find the scramble down a rock shelf onto the connecting land between the islets and I soon joined Adrian, Rob and Alex on the high point.  Adrian and Alex soon headed off and I remained with Rob for a few minutes talking about the Welsh Remotest list and Alan’s Sibs list, with the furthest northerly island which is named Ynys Berchen, being listed within each as a Pellennig and a Sub-Sib, Rob asked the criteria for the Pellennig list and wondered whether the small islet we were on would meet the minimum drop of 15m.  As he headed off toward the northerly Pellennig / Sub-Sib I set the Trimble up and gathered another five minutes of data from the high point of the southerly islet.

Alex scrambling back up the rock on his way past the Lighthouse toward Ynys Berchen

The Skerries Lighthouse from the summit of Ynys Arw

Ynysoedd y Moelrhoniaid bathed in sunshine

The northerly island of Ynys Berchen which is listed as a Pellennig and Sub-Sib

As the Trimble did its stuff I happily stared out on this stunningly beautiful place, content to be on my own soaking up its ambience.  By this time a few people were gathering, waiting to descend toward the RIB, and once the five minutes of allotted data were collected, I took a few photos with the Lighthouse shining white as a slight breeze blew in from the sea.

Gathering data from the summit of Ynys Arw

As I slowly made my way down the wet rock back onto the connecting pebbled and sea weeded land I wondered if I could make it to Ynys Berchen, but after scrambling back up the small rock shelf toward the Lighthouse I peered out and saw four small figures just turning their backs on the summit of the northerly island and heading back towards the Lighthouse.  My chance had gone as it would be unfair to keep everyone waiting another half an hour or so as I went over, gathered data and came back.  On occasions such as this I often reflect and store the memory of want, by doing so it encourages further visits, and these islands deserve that.  All too soon it was time to depart, we headed down to the metalled ladder and got back on the RIB and pulled out of the small, sheltered bay. 

Rob on his way down the ladder to the RIB

Getting ready to leave Ynysoedd y Moelrhoniaid.  Photo: RibRide

On our way back to Ynys Môn the islets of Ynysoedd y Moelrhoniaid were being enveloped by late afternoon high grey cloud as showers pushed in from the Irish Sea.  The RIB swept around their northern extremity before plunging back toward the Marina.  I looked back and the elongated profile of these wonderful rock strewn islets were now dark and silhouetted against the late afternoon sky, their illuminated colour now gone, replaced with a heartening profile of mystery and beckoning. 

The last view of Ynysoedd y Moelrhoniaid, now no more than a silhouette

Survey Result:

Ynysoedd y Moelrhoniaid 

Summit Height:  21.7m (converted to OSGM15) (Double Sub Twmpau addition)

Summit Grid Reference:  SH 26777 94759

Bwlch Height:  not applicable

Bwlch Grid Reference:  not applicable

Drop:  21.7m

Dominance:  100.00%

Ynys Arw 

Summit Height:  15.2m (converted to OSGM15, Trimble GeoXH 6000) (significant height revision)

Summit Grid Reference:  SH 26647 94598 (Trimble GeoXH 6000)

Bwlch Height:  0.0m (LIDAR)

Bwlch Grid Reference:  SH 26690 94671 (LIDAR)

Drop:  15.2m (Trimble GeoXH 6000 summit and LIDAR bwlch) (Pellennig addition confirmed) 

Dominance:  100.00% (Trimble GeoXH 6000 summit and LIDAR bwlch)

For further details please consult the Trimble survey spreadsheet click {here}

© Crown: CHERISH PROJECT 2019. Produced with EU funds through the Ireland Wales Co-operation Programme 2014-2020. All material made freely available through the Open Government Licence.