Showing posts with label Grindle. Show all posts
Showing posts with label Grindle. Show all posts

Thursday, 28 December 2023

Mapping Mountains – Significant Height Revisions – The Fours – The 400m Hills of England


Grindle (SO 430 926) 

There has been a Significant Height Revision to a hill that is listed in the The Fours – The 400m Hills of England, with the summit height, col height and their locations, the drop and status of the hill derived from LIDAR analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips.                                                                                                             

LIDAR image of Grindle (SO 430 926)

The criteria for the list this height revision affects are:

The FoursThe 400m Hills of England.  English hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are three categories of sub hills, the 400m Sub-Four category, the 390m Sub-Four category and the 390m Double Sub-Four category.  The list is co-authored by Myrddyn Phillips and Aled Williams and the 2nd edition of the booklet containing this list was published by Mapping Mountains Publications on the 24th April 2018.

The Fours - The 400m Hills of England by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Grindle, and it is adjoined to the Stiperstones group of hills, which are situated in the county of Shropshire close to the Welsh border, and it is positioned with minor roads to its north and west, and the B4577 and A49 roads to its east, and has the town of Church Stretton towards the east north-east.

When the 1st edition of the The Fours was published by Europeaklist in December 2013, this hill was listed with an estimated c 53m of drop, with a 459m summit height positioned at SO 430 926 based on the spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map and an estimated c 406m col height, based on interpolation of 5m contouring between 405m – 410m. 

Extract from the Ordnance Survey 1:25,000 Explorer map

When the 2nd edition of the The Fours – The 400m Hills of England was published by Mapping Mountains Publications in April 2018, this hill was listed with a 460.2m summit height, based on a Trimble GeoXH 6000 survey.

However, it was not until LIDAR became available that the details produced by the Trimble GeoXH 6000 survey for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR summit image of Grindle (SO 430 926)

LIDAR analysis gives the highest ground on this hill as 460.5m positioned at SO 43009 92663, and this is being prioritised over the result produced by the Trimble GeoXH 6000, and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 460.5m and this was derived from LIDAR analysis, this position is adjacent to where the 459m spot height appears on the Ordnance Survey 1:25,000 Explorer map and is 1.5m higher than it and importantly signifies contemporary Ordnance Surveys maps are missing an uppermost 460m ring contour. 

 

The full details for the hill are:

Group:  Stiperstones

Name:  Grindle

OS 1:50,000 map:  137

Summit Height (New Height):  460.5m (LIDAR)

Summit Grid Reference:  SO 43009 92663 (LIDAR)

Col Height:  406.6m (LIDAR)

Col Grid Reference:  SO 42581 92764 (LIDAR)

Drop:  53.9m (LIDAR)

 

Myrddyn Phillips and Aled Williams (December 2023)

 

 

  

Thursday, 20 February 2014

Mapping Mountains – Trimble Surveys – Stiperstones



19.02.14  Burway Hill (SO 440 942), Yearlet (SO 436 935), Pole Bank (SO 415 944), Grindle (SO 430 926) and Callow (SO 431 919)

Callow (SO 431 919)

What an absolutely wonderful day!  For many years I’d wanted to investigate the hills of the Long Mynd and especially their eastern ridges.  The OS map portrays a land of deep carved steam valleys with steep sided rounded hills rising to a relatively flat topped plateaux.  It was these eastern ridges I wanted to visit and the opportunity to do so presented itself when Charlie Leventon suggested a number of alternative routes we could do on the first available fine weather day.


Charlie Leventon on the way from Grindle (SO 430 926) toward Callow (SO 431 919)

We met in Little Stretton next to a bin at a junction of lanes (SO 441 919) where two or three cars can be squeezed to the edge of the road.  We then drove through Church Stretton and gained height above the Carding Mill Valley and made our way up to a pull in spot (SO 439 942) beside the col of Burway Hill.

The forecast for the day was good with sun breaking through high cloud cover in the afternoon.  As we left the car to investigate the col there was a slight breeze with freshness in the morning’s air.  The position of the critical col was easy to find as it was one of two places, each a few metres apart, we looked, judged, decided, and walked to the same spot.  Ten minutes of data later and we were heading up to the summit of Burway Hill (SO 440 942). 

This is a hill that Aled had prioritised for a Trimble survey and it was also a hill that Charlie was interested in, as the OS enlarged Geograph map gives a 373m spot height on the high road adjacent to where one would imagine the critical col to be placed and a 402m spot height on the summit.  Could Burway Hill be a new ‘Four’ with 30m of drop or with its current 29m of drop could it be deleted from the Sub-Fours in to the ranks of Double Sub-Fours as its absolute height is below 400m?

Burway Hill (SO 440 942)

From the aspect of the col the hill is pyramidal as it rises up to a pointed summit, its southern side plunges down to the Townbrook Valley, and with small crags and a rock outcrop at its upper section it is an excellent little hill.

We debated which of two possibilities was the highest, each only an inch or so different in height, once the Trimble had been balanced on our favoured chose and wedged in place with a few small rocks we wandered down the eastern side of the hill to look down its continuing ridge.  Once 11 minutes of data had been safely stored we descended to the car and drove a little way up the road to park in a better spot.

The Trimble GeoXH 6000 on the summit of Burway Hill

We then followed a contouring green path around the upper part of the Townbrook Valley that brought us to the col area of Yearlet (SO 436 935).  We took data at two points at the col and then headed up to the summit.  The hill has a steep graduated profile reminiscent of some Howgill fells in the Yorkshire Dales.

The summit of Yearlet (SO 436 935)

Charlie then led the way on another good path toward the high point of the Long Mynd; Pole Bank (SO 415 944).  This was the only hill of the Long Mynd that I had visited, the first time I have no recollection beyond the knowledge that I did visit, and the second time was with Bob Kerr in July 2012.  The summit has a trig pillar and a panoramic viewfinder; we again judged the ground for the high point and gathered another ten minutes of data.  During this time we struck up conversation with two couples, one about Munros and the other about the height of the hill.

At the summit of Pole Bank, the highest point of the Long Mynd (SO 415 944)

To the north-west was the Stiperstones, a dark jagged profile of rock outcrops and away to the south-west beyond Heath Mynd were ominous rain showers, quite distinct with lighter hued grey verging on white and spreading up valleys either side of dark low hills.  The wind direction came from these showers and unless steadfast in their current position they would soon inch their way toward us.

Leaving the summit of Pole Bank we passed cars on the high road that goes over the Long Mynd and thought about a lunch stop at Pole Cottage, which is no more than a dilapidated hut.  We decided to press on in the hope that if the rain did head our way we would at least have our back to it as we headed south-east past Round Hill toward the col of Grindle.

At this stage sustenance was needed, and as the Trimble gathered data at two points on the col, we settled down for sandwiches and chat next to the ancient Cross Dyke that passes over the hill.

Lunch break on the Cross Dyke at the col of Grindle

Charlie had told me that Grindle is his favourite Long Mynd hill as it has few visitors, the main paths of the ridge it stands on bi-pass its heathery summit, leaving it for the investigative by nature and the hill bagger.  The high point was chosen by Charlie and I proceeded to do a little gardening and cleared the area of heather.  During our time between Pole Bank and Grindle the sky had threatened rain but thankfully none had materialised and as the Trimble gathered its data the sun quickly broke through the cloud and illuminated colour started to appear.  Charlie then found an Ordnance Survey metal stud placed near to the summit cairn.  An opportunity to take data at this point with the Trimble could not be missed and by the time it was set up for more data gathering the sun was out and colour was bouncing out of the land.

The Trimble positioned on the OS metal stud beside the cairn on the summit of Grindle

Sometimes words are not enough to describe scenes of beauty, so hopefully the following images will do justice to the half hour of luxuriant colour we experienced whilst near the summit of Grindle.

The summit of Yearlet

The Trimble positioned on the OS metal stud beside the cairn on the summit of Grindle with Yearlet in the background

The Wrekin, The Lawley and Caer Caradoc

Looking down on Church Stretton

Charlie admiring the light on Yearlet


Looking down on the summit of Callow

Our last hill of the day was Callow (SO 431 919) and as we made our way around the top of Small Batch we stood and looked out on delicate subdued greens as the sun sank lower in the sky, casting lengthy blacks and greys on the landscape.  The half hour on Grindle and the walk to the col of Callow was quite magical.  But these moments do not last as the play of sun and cloud only give enhanced colour for limited periods and as the Trimble gathered more data at the col the magical element of the colour disappeared and the winter stillness returned.

The summit of Callow has a small cairn and high ground about 25 metres from it, we gathered data at these two points and left the hills of the Long Mynd, descending eastward down to the awaiting car in Little Stretton.  What a wonderful day!

The Trimble beside the small cairn on the summit of Callow

Charlie documents his walks on his Summitsup blog, please visit and enjoy his beautiful images. 

LIDAR image of Yearlet (SO 436 935)

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:



Summit Height:  402.8m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SO 44061 94220 (Trimble GeoXH 6000)

Col Height:  372.9m (LIDAR)

Col Grid Reference:  SO 43980 94263 (LIDAR)

Drop:  29.85m (Trimble GeoXH 6000 summit and LIDAR col)

Dominance:  7.41% (Trimble GeoXH 6000 summit and LIDAR col)





Yearlet

Summit Height:  466.1m (LIDAR)

Summit Grid Reference:  SO 43644 93518 (LIDAR)

Col Height:  413.7m (LIDAR)

Col Grid Reference:  SO 43412 93672 (LIDAR)

Drop:  52.5m (LIDAR)

Dominance:  11.25% (LIDAR)





Pole Bank

Summit Height:  516.6m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SO 41517 94440 (Trimble GeoXH 6000)

Col Height:  324.1m (LIDAR)

Col Grid Reference:  SO 40094 99560 (LIDAR)

Drop:  192.5m (Trimble GeoXH 6000 summit and LIDAR col)

Dominance:  37.26% (Trimble GeoXH 6000 summit and LIDAR col)





Grindle

Summit Height:  460.5m (LIDAR) (significant height revision)

Summit Grid Reference:  SO 43009 92663 (LIDAR)

Col Height:  406.6m (LIDAR)

Col Grid Reference:  SO 42581 92764 (LIDAR)

Drop:  53.9m (LIDAR)

Dominance:  11.71% (LIDAR)





Callow

Summit Height:  412.3m (converted to OSGM15)

Summit Grid Reference:  SO 43113 91917

Col Height:  369.1m (converted to OSGM15)

Col Grid Reference:  SO 43050 92161

Drop:  43.2m 

Dominance:  10.47%








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