Tuesday, 4 April 2017

Mapping Mountains – Trimble Surveys – Stiperstones

10.03.17  Caer Caradoc (SO 477 953, only col surveyed [SO 456 936], SO 45685 93617 data from LIDAR being prioritised)

The view south from the road bridge onto the critical col of Caer Caradoc

There is a perverse sense of enjoyment when surveying in unusual places, be it a field next to a road, on a road itself, on a driveway adjacent to a house or as in today’s example – a railway platform.

The col in question for today’s little adventure is adjoined to Caer Caradoc, which is listed as a Marilyn, Hump and Four, and it is placed either on, or near to the tracks adjacent to the platform at the railway station in Church Stretton.

I’d examined the positioning of this col via contours on the Ordnance Survey enlarged mapping on the Geograph website as well as having whizzed round the town in a Google car on Google Maps, I’d also made a mental note of the lay of the land adjacent to the railway station on a recent visit to the town.  The above indicated that the critical col is placed adjacent to the tracks of the railway.

I parked close to the platform on the eastern side of the railway which gives access over a foot bridge to the platform on the opposite side.  The foot bridge gives a vantage point looking down on the railway tracks as they disappear heading south, map contours indicate that the land in this direction is descending and although using ones eye to judge such a thing is not ideal, this looked like the case.  The view northward was obstructed by the road leading into Church Stretton as its bridge passed over the railway.

The view south from the foot bridge

The view north from the foot bridge

I’d previously judged where a suitable ten figure grid reference would be for positioning the Trimble and this was on the easterly sided platform and before setting the equipment up I waited for a train to pull out heading north.  As the Trimble ebbed down to its required 0.1m accuracy level before data should be logged another train pulled in, this time heading south, I waited until this had left before activating the Trimble for its five minutes allotted data collection.

Waiting to activate the Trimble as the southward bound train prepares to leave

As another train headed in from the south the last of the 300 allotted data points were stored and I closed the Trimble off just before the train pulled up.  Having measured the offset between the Trimble positioned atop my rucksack and the platform at its base, and also the offset between the platform and the gravel beside the railway tracks I now wanted to try and follow the valley to valley traverse from the railway platform.

I walked over the foot bridge to the western side of the railway and headed on to the B 4371 road that leaves the A 49 road and heads in to the town centre of Church Stretton, a 189m spot height appears on this road on the Ordnance Survey enlarged mapping on the Geograph website, visually the positioning of this spot height is on the upward part of the hill to hill traverse, therefore I dismissed it and concentrated my efforts on the northern side of the B 4371.

The view north from the road bridge

The col contours on the northern side of this road make their way toward the railway via a greened recreational area, on the opposite side of the railway tracks is a small industrial park, and I wandered round this assessing the lay of land in comparison to the adjacent railway track.  I concluded that the platform from where I collected data from is as good a place as any for the critical col for Caer Caradoc to be placed, with the caveat that the only natural ground remaining in this whole area is the scrub land immediately beside the railway, all other land has been terra-formed.

Happy with my morning’s exertions I headed back to my car and proceeded toward Worcester for a few relaxing days of good company, good food and good conversation.

Survey Result:

Caer Caradoc (significant name change)

Col Height:  185.3m (converted to OSGM15) (186.5m col data from LIDAR being prioritised)

Col Grid Reference:  SO 45618 93614 (SO 45685 93617 col data from LIDAR being prioritised)

Drop:  274.2m (converted to OSGM15) (273.0m col data from LIDAR being prioritised)

Dominance:  59.68% (59.41% Trimble summit and LIDAR col)

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