The Mountains of Snowdonia

1:10,000 resurvey mapping

Note: The map at the foot of the page outlines the extent of the 1:10,000 resurvey work compelted by KJM. It does not include the work covered by other members of the section or any 1:2500 surveying

1974 summer season

The season started after the training in late May in north east Snowdonia (near Conwy) and I can still remember the terrific views from the Foel Lus slopes above Penmaenmawr and Dwygyfylchi.

The above image was taken on 29 May 1974 from Foel Lus - looking west towards the Penmaenmawr quarries [and the neolithic axe factory] and Anglesey across the water. Despite some serious sunburn one glorious Friday, the mapping moved quickly onto Tal y Fan, Bwlch y Ddeufaen and Llyn Eigiau. In addition to witnessing the year of the sheep farmer and key events in their calendar there was also a lot of history in the mountains.

At one set of stone sheep pens up in the hills above Eigiau I stopped to chat to the sheepmen and was appalled to see them castrating young lambs - just using a set of tongs. Eigiau was also the source of tragedy in 1925 when the poorly constructed dam broke, the water rushed to the edge of the Conwy valley where it broken through a second dam high up on the edge of the main valley. This flooded the village of Dogarrog with the loss of 17 lives.

Occasionally we would discover the remains of aircraft that had crashed up in the cwms.

%eigiau dam%
The above image was taken on 01 July1974 of the Eigiau dam wall - from inside the original reservoir looking east. The gap in the wall is the section that collapsed in 1925.

Then work moved onto the two big Cardneddau: Carnedd Llewlellyn & Carnedd Dafydd as well as Pen yr ole Wen. Every part of the ground had to be covered and ensured the surveyor reached places few others had ever even heard of such as the view of Ysgolion Duon cliffs on the north west side of the ridge between the two Carneddau.

ogwen guidecard
A section of a "guidecard" used in the preparation and production of sheet SH66SE which covered Ogwen and the Carneddau.
The card shows benchmarks and other items marked up to requiring specific attention. The card was an existing 1:10,560 map manually altered to align with the National Grid. It was the 19thC mapping with contours - limited to 1000 feet.

The material we used in the resurvey was plastic "super astrafoil" sheets 500mm x 500mm. The sheets were prepared by Air Survey Branch based on a new aerial triangulation for each block of work. The operator employed an overlapping pair of aerial images in a precision instrument to identify and plot all features that were visible in the area of survey - as well as contour the entire sheet. Our task was to ground complete the map by adding features that the operator had missed or could not see (eg wire fences or features under trees). All features were described by annotation and terrain vegetation classified. We also added other items such as names, bench marks, boundaries etc.

%ysgolion duon%
The above image was taken on 17 July1974 of Ysgolion Duon and is one of several forming a wide panorama.
The height of the cliffs can be judged by the size of the wild horses in the bottom left. Access to the Afon Llafar valley was from the outskirts of Bethesda several km away. In Spring 1974 Ordnance Survey released its first set of 1:50,000 maps - all based on One-Inch cartography except two - one of which was the Snowdonia sheet. Wiithin a week there was a furore in the press because the new District boundary symbol resembled that of a footpath. One section of boundary came off the top of Carnedd Dafydd - ie off these cliffs. OS responded by changing the symbol and putting a "warning sticker" on all unsold Snowdonia maps.

So good was it that I walked the Ogwen-Carneddau-Llugwy-Ogwen circuit for work during the week and then repeated it again at the weekend for fun.

1975 winter season

It was not planned but in early 1975 I was asked to undertake sheet SH65NE. This was because there had been a theft in the Porthmadog section late the previous year and one of their completed 1:10,000 sheets had been stolen. To make up "completed km survey" figures for the financial year SH65NE was selected.

The full sheet [25 square km] took in Tryfan, Glydyr Fach, Dyffryn Mymbyr and Pen y Gwryd [used by the Everest team when testing equipment - see note below] . As snow and ice was thick on the ground I was accompanied on the main ridge walk by John Finlay fthe Porthmadog office manager (and who at that time lived in the old police house in Capel Curig and was an experienced mountaineer).
%cardigan bay%
The above image was taken on 16 January 1975 from Glyder Fach towards Porthmadog and Cardigan Bay in the distance. Lliwedd, from the Snowdon group, is on the right topped by the amazing cloud formation.

Dyffryn Mymbyr
The above photo is of Dyffryn Mymbyr [farm] taken on 20 January 1975 the farm is in the trees on the hillside.

Dyffryn Mymbyr is immortalised in the book "I Bought a Mountain" by Thomas Firbank - a true story based in the early 1930s. Arriving from Canada and still in his early twenties he bought the farm in 1931. He married Esme Cummins and the story describes their success and failure managing a sheep farm over a decade - up the the start of the war. Though the pair then split up [he went on to win an MC in Italy in 1943] - Esme remarried and she was still living at Dyffryn Mymbyr farm when I surveyed the area in early 1975. In fact she signed an "OS232" for me - a form used to approve change of "distinctive" name eg buildings etc.

In total I surveyed 126 km sq in North Wales over this period in 555 hours, a rate of 4.4 hours a km.This includes all work on the sheet except travel time to the site and any stoppages due to bad weather.

Updated: KM18 August 2013


Snowdonia, North Wales


Start: 30 April 1974
End: 31 Jan 1975


Penmaemawr: Wikipedia summary
1925 Llyn Eigiau tragedy: Wikipedia summary
Pen y Gwryd & the Everest team: Wikipedia article
"I bought a mountain": by Thomas Firbank
"Dyffryn Mymbyr": the farm today