Mapping Mountains – Trimble Surveys – Pumlumon

07.02.14  Y Gaer (SO 013 873), Gelli Hir (SN 999 883) and Cefn Carnedd (SO 015 899)

This is the first of two Trimble surveys of Y Gaer and Gelli Hir, to read the second survey post please click {here}

Y Gaer (SO 013 873)

I’d first visited these hills on the 17.01.04, long before P30’s became fashionable.  On my first visit I’d bagged each from the most convenient parking place, today I wanted to combine them in a circular walk and investigate different approach and descent routes.

As the forecast was the most optimistic for the past few days I took advantage, even though a persistent head cold had plagued me for a number of days.  Hopefully a steady wander in sunshine might sweat the symptoms out of me.

I parked close to the Water Works (SO 021 893) on the outskirts of Llandinam and headed south up the Waen Lane.  I soon realised that the most appropriate footwear for the day was wellies as the fields were awash and particularly muddy.  Leaving the lane a footpath follows the crest of the Y Gaer ridge and eventually enters forestry known as Coed Mawr.  By this stage my boots were covered in liquid mud so I clambered a fence and walked in the field, passing the remains of a house on my way to the highest point.

The summit consists of close cropped grass and is placed near a few trees.  It wasn’t difficult to assess the territory and find the high point.  I’d brought the Draper tripod and external antenna just in case the tree coverage was problematic for the Trimble’s internal antenna.  Deciding not to use the tripod I set the equipment in place and then waited about 20 minutes for it to attain its 0.1m accuracy before pressing ‘Log’ to start gathering data.  This time delay was probably due to the proximity of the trees, every couple of minutes I would sneak up on the Trimble and see if the required accuracy had been attained, only to quickly sneak off again when it had not.  This procedure happened on a number of occasions.  My only companions were an investigative herd of sheep who seemed particularly interested in my exploits.

Looking back toward the high point of Y Gaer

Attentive surveying companions

Once 10 minutes of data was gathered I headed down on footpaths towards the farm named Cefn (SO 006 868) where I surprised Graham Pugh as he came out of a barn full of recently born lambs.  I apologised for surprising him and explained where I had come from and where I was heading.  We were soon talking about the name of the hill, something I hoped to have confirmed and who better to ask than the farmer who lives and works immediately below it.  Graham knew the hill as The Gaer (Y Gaer on the map) after the ancient hill fort north of the summit.  I asked if he’d ever heard of Coed Mawr, he had but only as the name of the farm at (SN 990 889), he certainly didn’t know the hill as Coed Mawr.  When I asked him about the other 308m summit (SN 999 883) he explained that he didn’t know a specific name for it but he’d recently talked with the person from the farm of Coedmawr who had purchased the land and he called it Gelli something.  This last part I found particularly interesting as the Sub-HuMP is currently named Rhos Fawr, this name applies to the farm at SN 996 884 and not the hill.  I’m as guilty as other hill list compiler’s as I’d also used the names of Coed Mawr and Rhos Fawr when compiling the Welsh 300m P30 Hills that was published on Geoff Crowder’s website in 2002.  The Ordnance Survey Seventh Series, New Popular and Historical 1:25,000 maps are all better for name placement when compared to current maps, especially so for the latter of these three.  One tendency with current maps is to align most if not all names horizontally, whereas many of the older maps had ridge names following the ridge, a practice that makes picking the most appropriate name much easier.  Examine these three older maps and see where the name Gelli Hir is placed compared to its current position and you’ll be able to form a much better viewpoint on the most appropriate name of the hill.

Graham Pugh at the farm of Cefn

We spoke for 15 minutes or so and then he started talking about hills with 100m of rise and people who visited the hill from all manner of places, including an elderly man who walked slightly hunched over with the aid of two poles.  Graham had chatted to this person and wondered if he could make it to the top of the hill, the man replied ‘of course I will no problem’.  It was then I showed him the Trimble and explained that I was de-twinning a HuMP, ‘that’s it’ he said ‘the HuMps’ ‘there’re the hills these people go up, they come from all over, many in quite posh cars’, well that last bit rules me out then!

Graham was good enough to show me a short cut over his fields that bi-passed the footpath and headed towards Gwastadcoed (SO 001 872).  Soon I was on another lane and approaching the critical bwlch between the summits of the Twin HuMP.  This is where a 217m spot height appears on the Ordnance Survey enlarged Geograph map.  I always write these posts before processing the data as I don’t want to be influenced by the result, and in the instance of this OS spot height, the processed height is still unknown but the position is absolutely correct as when I walked down the lane, the valley to valley traverse ascended on my right and left and the continuation of the hill to hill traverse carried on up the lane.  I picked my spot beside the road and gathered another 10 minutes of data.

The Trimble GeoXH 6000 beside the road at the bwlch between the Twin HuMP

I then called in at Rhydfaes (SN 997 872) for more place-name enquiries.  Tim had lived in the area all his life and was very helpful, he was under the impression that Coed Mawr related to the wood rather than the hill.

From Tim’s house I followed a track up on the eastern side of Gelli Hir and proceeded to take two data sets.  One on the first high point I reached and the second at the summit of the hill.  Again, my only companions were a number of sheep.  By now the sun was relatively low in the sky casting long shadows and illuminated colour.

Gathering data at the summit of Gelli Hir

Gelli Hir (SN 999 883) seen from the summit of Y Gaer (SO 013 873)

Descending to the track I followed it north-eastward down to another lane where the critical bwlch of Cefn Carnedd is positioned.  If my head cold and time allowed, I wanted to take in this final summit of the day and so I placed the Trimble beside the road and switched it on to gather data, a couple of minutes later there was a rumble and a huge forestry lorry full of felled trees chugged up the narrow lane and missed running over the Trimble by no more than two feet, mind you by this stage I was standing beside it so I was going to get squished first if any squishing was going to take place.  The Trimble has a ‘Pause’ key and I should have used this when the lorry appeared, I didn’t think, my first thought was to stand close to it to stop the lorry causing an expensive accident.  Because of this the data set should be interesting as the lorry blanked out half the sky for 30 seconds.

LIDAR image of Gelli Hir (SN 999 883)

My last hill of the day; Cefn Carnedd proved steep and in a number of places; waterlogged.  The hill has an impressive ancient enclosure taking in its summit that measures 437m by 84m and consists of triple banks and ditches to the north-west.  The high point of the hill is on one of the ancient earthen banks.  The Trimble was set on the high point and gathered 11 minutes of data - modern technology placed on pre-historical earthen ramparts.

The summit of Cefn Carnedd (SO 015 899)

The route back to the car overlooked the Severn valley and the Afon Hafren as it meandered through the flat greenery, over spilling its banks.  It had been an excellent day on fine small hills and a rarity weather wise as the sun shone out of a blue sky.

The Afon Hafren outside of Llandinam

Survey Result: 

Y Gaer (significant name change)

Summit Height:  307.1m (converted to OSGM15)

Summit Grid Reference:  SO 01350 87380

Bwlch Height:  215.8m (converted to OSGM15)

Bwlch Grid Reference:  SO 00054 87410

Drop:  91.3m  (de-twinning with prioritised Hump reclassified to Subhump)

Dominance:  29.74% (Lesser Dominant deletion confirmed)

Gelli Hir (significant name change)

Summit Height:  307.2m (converted to OSGM15)

Summit Grid Reference:  SN 99902 88383

Bwlch Height:  182.5m (LIDAR)

Bwlch Grid Reference:  SN 9723 88327 (LIDAR)

Drop:  124.7m (de-twinning with prioritised Subhump reclassified to Hump)

Dominance:  40.60% (Lesser Dominant addition confirmed)

Cefn Carnedd

Summit Height:  280.0m (converted to OSGM15)

Summit Grid Reference:  SO 01563 89926

Bwlch Height:  203.8m (converted to OSGM15)

Bwlch Grid Reference:  SO 00942 89349

Drop:  76.2m

Dominance:  27.23%

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