Mapping Mountains – Trimble Surveys – Stiperstones

25.01.14  Heath Mynd (SO 335 940) and Cefn Gunthly (SO 331 948)

Heath Mynd (SO 35 940)

There’s something very satisfying in the knowledge that hills have been visited before thunder, lightning and a deluge of heavy hail descends upon the land.  The weather forecast predicted a fine morning with the next westerly front bringing its customary winter greyness and rain arriving by early afternoon.  The forecast was spot on.

The intention was to visit three hills over two walks and survey each summit and at least two of the cols.  The third col was an option depending upon the weather front and the position of the col, as maps had the spot height on an A road outside a large house.  Not ideal, as the Trimble is still only young and I didn’t want it squished by passing traffic.

For many years my intended direction was heading west as that’s where the higher hills lie, occasionally trips south were planned to visit Bannau Brycheiniog, and since joining up with John and Graham our surveying trips have pushed us northward, but heading east is a rarity.  East is in to England and away from the high hills, but my priorities have changed over the years.  Now I get as much satisfaction from visiting a relatively low hill than a high one.  And more so if I haven’t visited the former as that will mean new territory being explored.

I’d visited Heath Mynd once before with Bob Kerr and Sarah on a late evening when the sun cast magical colour in the west, but Cefn Gunthly was missed that day, so my new hill could be visited and a circular route over the two hills seemed feasible from the south-west.

Bob and Sarah at the summit of Heath Mynd

The morning was still and grey when I set off up the southerly slopes of Heath Mynd, by 8.15am I was standing at the top looking over at Corndon as the cloud slowly lapped at its summit.  Grey predominated with only a hint of a sliver of brightness to the east as the sun struggled behind the cloud.

The summit area of Heath Mynd has a trig point and an ancient cairn on it.  The cairn is quite substantial in girth if not height.  The vegetation on the upper slopes is heather, at the periphery of the cairn the heather had overwhelmed the outer limits of the cairn and was now growing over the rock.

I considered setting the Trimble up at the base of the cairn’s periphery, but the vegetation that had now taken over the outer limits of rock has peat at its base, I considered this a sign that at least part of the ancient cairn was now a part of the hill and placed the Trimble on the ground and collected 11 minutes of data.

The summit area of Heath Mynd with its trig and ancient cairn

As I descended northward toward a track that contours the hill to the connecting col with Cefn Gunthly, the first sign of brighter skies started to show, below me a farmer was out on his quad bike laying out feed for the sheep.  Otherwise the land was all quiet with the summit breeze disappearing just below the upper part of the hill.  Soon the quad bike went on its way leaving me access to the green upper hillside of Cefn Gunthly.  Two gates were conveniently open and soon I was at the top, this consists of what looks like the remains of an ancient tumulus, rounded with rocks beneath the cultivated grass.  The Trimble gathered 10 minutes of data and I then retraced my way back to the col between the two hills, stepping ankle deep in liquid slurry on the way.

Corndon from the summit of Cefn Gunthly

The col has the marks of a vehicle track passing over it in the valley to valley direction, I placed the Trimble in the position I favoured for the critical col and gathered more data.  A few metres away the land at the base of a fence looked slightly better placed but it consisted of liquid mud and I didn’t want the same unfortunate thing happening to the Trimble as had happened to my boots!

The view of Cefn Gunthly from the descent back to the narrow lane after gathering data at the col

After another 10 minutes of data had been gathered I followed the vehicle track down to the narrow lane and walked back to the car, watching a farmer round up his flock of sheep in an adjacent field on the way. 

Rounding up the sheep

The walk had only taken two hours but it left a magical sense of peacefulness until I met the flock of sheep being driven by quad bike and dog down the road and encountered a convoy of vehicles heading in the opposite direction to me.  Tis a very narrow road hereabouts with few options for passing, after the sheep had been skilfully directed in to another field I headed toward the next survey; Black Rhadley Hill.

After visiting Black Rhadley Hill I decided to investigate the col position for Heath Mynd.  The hill is listed as a Marilyn, HuMP and Four and has a 292m spot height on the OS 1:50,000 map as well as the OS enlarged Geograph map at SO 32387 94521.  This spot height appears in the centre of the A488 as it makes its way towards Shrewsbury.

Once parked I headed toward where the 292m spot height appears on the ground, this is at the entrance to Pultheley Farm where an attentive dog gave my presence away with a lot of barking.  As the track headed in to the farm it seemed to gain height, as indeed did the track that headed in to Pultheley Bank which has an entrance just south of where the spot height appears.  This signified that the critical col wasn’t anywhere near the barking dog.  I contemplated putting the Trimble on the ground at this entrance and gathering data to compare the processed height with that of the spot height, but across the road on its western side the ground fell away to a large pond.  On the north side of this large pond was a boggy quagmire with horses grazing nearby.  The water in the quagmire seemed not to want to go anywhere, but the map indicates that this is an outflow and therefore the high land on the valley to valley traverse must be to the south of the pond.  Rather conveniently this was where I had parked my car, which was pulled in beside the entrance to Lower Bank Farm.

Gathering data on the southern side of the large pond at the col area of Heath Mynd.  The A488 is just to the right of the photo with the ground where the 262m spot height is positioned about 80 metres up the road.

    

I then left the barking dog and walked back to the car and the southern side of the large pond.  It was relatively easy to judge the land on the hill to hill traverse, but more difficult for the land on the valley to valley traverse, and as I was now positioning the Trimble on grass beside the track that led up to Lower Bank Farm I didn’t want to wander around in the adjacent field and spend a lot of time trying to distinguish where the absolute critical col was exactly positioned.  Beside the track looked good to me and so I started the Trimble gathering data and retired to the side of the car.  Ten minutes later I switched it off, packed it away and headed for a shop at Tesco’s in Welshpool and made it home just as the sky turned a thunderous grey and hail started to batter everything in its path.  And only an hour earlier I’d been standing in the sun, happy in the knowledge that all objectives had been surveyed and the hills had proved peaceful places. 

LIDAR image of Cefn Gunthly (SO 331 948) and Heath Mynd (SO 335 940)

Postscript:

Since the survey of these hills full LIDAR coverage is now available.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height and positional data that is now freely available for England and Wales.  Consequently the numerical details for these hills have been analysed using this technique, resulting in the LIDAR height and position for some of these hills being prioritised over that produced by the Trimble GeoXH 6000.

Survey Result:

Heath Mynd

Summit Height:  452.6m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SO 33559 94091 (Trimble GeoXH 6000)

Col Height:  261.9m (LIDAR)

Col Grid Reference:  SO 32354 94433 (LIDAR)

Drop:  190.7m (Trimble GeoXH 6000 summit and LIDAR col)

Dominance:  42.14% (Trimble GeoXH 6000 summit and LIDAR col)

Cefn Gunthly

Summit Height:  400.8m  (converted to OSGM15, Trimble GeoXH 6000) 

Summit Grid Reference:  SO 33119 94831 (Trimble GeoXH 6000)

Col Height:  354.3m (LIDAR)

Col Grid Reference:  SO 33283 94544 (LIDAR)

Drop:  46.5m (Trimble GeoXH 6000 summit and LIDAR col)

Dominance:  11.61% (Trimble GeoXH 6000 summit and LIDAR col)

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