Mapping Mountains – Trimble Surveys – Moel Hebog

15.06.15  Moel y Gadair (SH 521 391)  

Moel y Gadair (SH 521 391)

Having visited and surveyed Carreg yr Eryr (SH 526 378) my next objective was Moel y Gadair which is situated next to the A 497 as it heads west from Porthmadog to Cricieth.  I parked just off the road next to a hotel and walked back up the road as I had spotted a right of way that I thought may give good access to the hill.  Before reaching the right of way I decided to try my luck at a house which had a track leading to it and which was conveniently nestled directly under the hill.  I knocked on the front door and someone appeared at a window looking as if they had only just woken up.  I explained where I planned on going and asked if it was all right for me to gain access to the hill from the back of the house.  The person replied that the land was private, this wasn’t a good start, especially so after I had reiterated my question and the same reply was forthcoming.  I persevered, but tried a different line of approach and asked if they would have any objection in me visiting the hill from the adjacent field to their house, they did not, I thanked them, quickly disappeared around the side of their house, jumped onto their garden wall and clambered over a barb wired fence into the adjacent field and proceeded to clamber up a bank and over another fence to open pasture and quickly headed for the summit of the hill.

Away to my east the eloquently shaped Moel y Gest rose above the land, a shapely small hill if ever there was one.  The high point of Moel y Gadair was not difficult to pinpoint and within a couple of minutes the Trimble was gathering data.

Moel y Gest from the summit of Moel y Gadair

Gathering data at the summit of Moel y Gadair

Once the Trimble was packed away I considered heading west and gaining a right of way back to the car and the bwlch which I now wanted to survey, but during the time the Trimble was gathering data I had walked a few metres north to inspect the lay of the land at the bwlch and found that the hill to hill traverse headed down the route of my inward walk, so I headed back down the same way I had come but avoided the garden wall and walked down the field to a conveniently placed gate which gave access onto the track and then the road.  It was then that my mind became muddled; I only found this out later when inspecting large scale maps, as when I arrived on the road I got the directions of part of the valley to valley traverse mixed up with part of the hill to hill traverse.  At the time I did not know this and happily collected data at the high point of the road thinking that this was a candidate for the bwlch.  It wasn’t, but I didn’t realise it then.

Gathering data at the high point of the road

I then walked down the road thinking that I had to find lower ground on the hill to hill traverse, which in reality was on the valley to valley traverse, because of this I found what I thought to be the low point of the road and then walked down to the side of a house, no one answered when I knocked on the door, so I quickly set the Trimble up thinking I was at or very near to the critical bwlch.  I was not, but I didn’t realise it then.

One option for the position of the critical bwlch of Moel y Gadair is where the white van is positioned

Gathering data beside the house

Happy that I had successfully captured all important data from the side of the house I decided that I should see if lower ground existed by a series of lakes that did not appear on my 1:25,000 map but had been built relatively recently as they appeared on larger scale on-line mapping that I had inspected.  I jumped in my car and drove down a rutted track and parked beside the fishery café.  I then spent a leisurely 30 minutes wandering around the lakes thinking that I was still on the hill to hill traverse when in fact I had descended on the valley to valley traverse.  Whatever my mishap I had a very pleasant time beside the lakes and found a stream on their periphery which I followed uphill until it swung around, I thought this indicated that the critical bwlch lay the other side of the steam, this deduction was correct but not in the place where I thought it should be.  It must have been the heat of the afternoon, or possibly the built up environment, or even my bad eyesight as the detail on the map was beyond my fathoming even wearing glasses!

One of the lakes at the Eisteddfa Fishery

Happy that I had found another potential place for the critical bwlch I placed the Trimble beside the water’s edge of the carp lake and waited for it to achieve its 0.1m accuracy before data can be logged.  This took quite some time as the whole area was enclosed with overhanging trees, however the Trimble did manage this accuracy and ‘Log’ was pressed.  During this wait I chatted to Trefor Owen and his grandson; Thomas Owen, who were relaxing for the day fishing.  Trefor originated from Rhyl, he could speak Welsh and spent many years living in Manchester.  He had brought his four sons up, none could speak Welsh but he seemed proudly happy that two of his grandchildren could now speak the language to an adequate level, including Thomas.

The Trimble gathering data beside the Carp Lake

Trefor and Thomas Owen enjoying their fishing

All catches were quickly put back in the water

As the Trimble gathered the last data point and the five minutes were up, I switched it off, packed it away, chatted with Trefor and Thomas, took a few more photos of the lakes and walked back to my car in the knowledge that I had found the bwlch position of Moel y Gadair.  Of course this was delusional and I will have to go back at a later date, however I know now where the critical bwlch lies, so I’ll have no problem on my next visit in identifying its position, well I don’t think I will!?!?

Postscript:  Since the survey of this hill, the LIDAR (Light Detection & Ranging) technique is now being used to produce accurate height and position for hills.  Subsequently this hill has been analysed via LIDAR.  The details produced by the Trimble GeoXH 6000 summit survey are retained; however LIDAR bwlch contouring indicates this hill is a natural P30 with LIDAR giving a height and position for a bwlch with remaining natural ground close by and indicating the road passing over the bwlch has been artificially raised.  Therefore, as the road is considered a recent man-made construct it is excluded from the height of the bwlch, with the listed height and position of the bwlch that indicated by LIDAR analysis resulting in the confirmation of this hill being classified as a P30.

Survey Result:

Moel y Gadair

Summit Height:  66.7m (c0nverted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 52165 39135 (Trimble GeoXH 6000)

Bwlch Height:  35.8m (LIDAR)

Bwlch Grid Reference:  SH 52013 39319 (LIDAR)

Drop:  30.9m (Trimble GeoXH 6000 summit and LIDAR bwlch) (30-99m Twmpau reclassified to 30-99m Sub-Twmpau) (Lesser Dominant deletion) (30-99m Sub-Twmpau reclassified to 30-99m Twmpau) (Lesser Dominant addition)

Dominance:  46.30% (Trimble GeoXH 6000 summit and LIDAR bwlch)

For the post detailing the bwlch survey of Moel y Gadair please click {here}

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