Mapping Mountains – Trimble Surveys – Moel Hebog

01.02.14  Ynys Hir (SH 566 396), Pt. 36.9m, Ynys Hir (SH 566 398) and Ynys Fadog (SH 564 398)

The wooded summit of Ynys Fadog (SH 564 398)

The ‘islands’ of Ynys Hir and Ynys Fadog are just some of the many small outcrops of land that are now landlocked having once been islands in the tidal estuary of Afon Glaslyn.  They are on the flatland's known as the Traeth Mawr, the translation of which can be ‘large beach’ or ‘big sands’.  Each is situated on the outskirts of, and between Porthmadog and Tremadog with the flatland's having been reclaimed from the sea in the late 1700’s. 

The Traeth Mawr extends north-eastward from Ynys Hir and Ynys Fadog toward Nantmor, whist following this reclaimed land on the map one is struck by these landlocked islands, many are wooded and some are P30’s.  It was our intention to survey the two ‘islands’ known as Ynys Hir and the one known as Ynys Fadog, the latter seems lower in height when compared to the other two, but all three have an uppermost c 20m contour on current Ordnance Survey maps.  All three are densely wooded, could one or two of them attain P30 status?  

Our intention had been to re-survey Foel (SH 450 506) for potential HuMP status, but the forecast was so dreadful that Aled suggested a wonder in a wood, as this would give us shelter from the predicted rain and high wind and would give Twm (Aled’s dog) a good bit of exercise, as well as giving each ‘island’ an absolute height, something that they lacked on any Ordnance Survey map we had examined.

We met at 9.30am and spent the next 90 minutes chatting in Aled’s van as the rain swept in.  Once there was a break in the wet stuff we gathered Twm up and set out in to the wood.  Once beneath the trees it was like entering another world, one consisting of canopy, steep slopes and cliffs.  These islands may be low in height but they are little marvels, packed full of interest and undergrowth.  Paths exist in the wood, mainly at lower elevation around the base of each ‘island’, and stone steps partly up them (if found), otherwise they are overgrown in fern, bramble, ivy and copious amounts of trees.  Interspersed amongst the pleasantries of foliage is rock, much of this is cliff shaped and some overhanging.  Ways to each summit do exist but much of it is through branches on a zig zag route ever upward.

The whole wood is known as Y Nursery, with the island at SH 566 396 and SH 566 398 both being known as Ynys Hir.  We headed for the one at SH 566 396 first and encountered steep rising ground full to the brim with lots of undergrowth and woody stuff.  Aled led the way closely followed by Twm and soon found a series of stone steps that gained height around the middle section of the hill.  Further progress involved bashing through branches until we reached the high point.  Beside this was a telegraph pole, looking rather out of place amongst the ivy, bramble and detritus.  We set the Trimble up on its pole and stuck it in the earth taking a measurement from tip of screw (just under the antenna) to ground level and input this in to the equipment as a measurement offset.  The antenna was fixed in place and we gathered 18 minutes of data.  The downward route was as much fun as the upward, full of interest and swacks in the face by branches.

Aled and Twm beside the high point of Ynys Hir (SH 566 396)

We considered surveying the bwlch between the two summits known as Ynys Hir but pressed on to the second summit.  More stone steps led up the middle part of the hill past an impressive overhanging cliff and then it was bush whacking again as the summit was eventually reached through a thick passage of intervening shrubbery.

Underneath the overhanging cliff on our way up to the second summit.

The high point consisted of a rock on top of a larger rock with the customary amounts of ivy, fern and all sorts of Tolkienesque forms of undergrowth pervading everything in sight.  Near to the high point a gap in the trees gave us a view toward our first wooded island and our yet to be visited wooded island; Ynys Fadog.  Close by was a cliff.  Twm was settled beside a tree as the Trimble was again set up on its pole; we gathered ten minutes of data and found an easier slithery way down.

The high point of the second summit (SH 566 398)

The third island was by far the easiest to get to the top of, once there the pole was pushed in to the earth beside the high point, which was another small rock.  We measured from the tip of the screw thread to the tip of the rock, put this measurement offset in to the equipment and set it gathering data.

At the summit of Ynys Fadog (SH 564 398)

The day had proved quite an unexpected adventure on small islands of overgrown wonder that are well sheltered and rather magical.

Survey Result:

Ynys Hir

Summit Height:  37.3m (converted to OSGM15) (significant height revision)

Summit Grid Reference:  SH 56695 39693

Drop:  c 34m (30-99m Twmpau addition confirmed)

Dominance:  91.21% (Dominant addition confirmed)

Pt. 36.9m, Ynys Hir

Summit Height:  36.9m (converted to OSGM15) (significant height revision)

Summit Grid Reference:  SH 56649 39840

Drop:  25.8m (converted to OSGM15) (30-99m Sub-Twmpau addition confirmed)

Dominance:  69.90% 

To read the blog post on the survey of this hill’s bwlch please click {here}

Ynys Fadog

Summit Height:  27.8m (converted to OSGM15)

Summit Grid Reference:  SH 56464 39823

Drop:  c 25m (Double Sub-Twmpau addition confirmed) 

Dominance:  89.77%

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