Showing posts with label Castle Hill. Show all posts
Showing posts with label Castle Hill. Show all posts

Tuesday, 9 March 2021

Mapping Mountains – Significant Height Revisions – 200m Twmpau

 

Castle Hill (SO 314 945)

There has been a Significant Height Revision to a hill that is listed in the 200m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data, a Trimble GeoXH 6000 summit survey and subsequent LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Castle Hill (SO 314 945)

The criteria for the list this height revision affects are: 

200m Twmpau – Welsh hills at or above 200m and below 300m in height that have 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 200m Twmpau by Myrddyn Phillips

The name the hill is listed by is Castle Hill and it is adjoined to the Stiperstones group of hills, which straddle the border between Wales and England with the Welsh part of this group situated in the north-eastern part of South Wales (Region B, Sub-Region B2), and it is positioned with the A490 road to its west, the A489 road to its south and the A488 road to its east, and has the small community of Hyssington towards the south-west. 

When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the accompanying Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.  

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 24m of drop, based on an estimated c 281m summit height and the 257m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was named the Interactive Coverage Map. 

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

Since the original compilation of this list there have been a number of Ordnance Survey maps made available online, some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website, whilst others are current and digitally updated such as the mapping on the WalkLakes website and the Magic Maps website. 

One of the mapping resources now available online is the Magic Maps website which hosts an interactive map originated from Ordnance Survey data.  This map has many spot heights not on other publicly available Ordnance Survey maps and for this hill a 283m spot height is given on the area of its summit. 

Extract from the Magic Maps website

The summit of this hill has now been surveyed with the Trimble GeoXH 6000, resulting in 283.2m at SO 31430 94540, and this height 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 summit 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. 

The Trimble GeoXH 6000 gathering data at the summit of Castle Hill

However, it was not until LIDAR became available that the details 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.

Therefore, the new listed summit height of this hill is 283.2m and this was derived from a Trimble GeoXH 6000 survey, this is positioned at SO 31430 94540 and is 2.2m higher than its originally listed height of c 281m which was estimated from the uppermost 280m contour on the contemporary Ordnance Survey 1:25,000 Explorer map. 

 

The full details for the hill are:

Group:  Stiperstones 

Name:  Castle Hill 

OS 1:50,000 map:  137

Summit Height (New Height):  283.2m (converted to OSGM15, Trimble GeoXH 6000) 

Summit Grid Reference:  SO 31430 94540 (Trimble GeoXH 6000) 

Bwlch Height:  258.6m (LIDAR) 

Bwlch Grid Reference:  SO 31415 94604 (LIDAR) 

Drop:  24.6m (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

Myrddyn Phillips (March 2021)

 

 

 

 

 

Sunday, 7 March 2021

Mapping Mountains – Hill Reclassifications – 200m Twmpau

 

Castle Hill (SO 314 945) – 200m Sub-Twmpau addition

There has been confirmation of an addition to the list of 200m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail on contemporary maps produced from Ordnance Survey data, a Trimble GeoXH 6000 summit survey and subsequent LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Castle Hill (SO 314 945)

The criteria for the list that this addition applies to are: 

200m Twmpau – Welsh hills at or above 200m and below 300m in height that have 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 200m Twmpau by Myrddyn Phillips

The name the hill is listed by is Castle Hill and it is adjoined to the Stiperstones group of hills, which straddle the border between Wales and England with the Welsh part of this group situated in the north-eastern part of South Wales (Region B, Sub-Region B2), and it is positioned with the A490 road to its west, the A489 road to its south and the A488 road to its east, and has the small community of Hyssington towards the south-west.

When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the accompanying Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 24m of drop, based on an estimated c 281m summit height and the 257m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was named the Interactive Coverage Map. 

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

Since the original compilation of this list there have been a number of Ordnance Survey maps made available online, some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website, whilst others are current and digitally updated such as the mapping on the WalkLakes website and the Magic Maps website. 

One of the mapping resources now available online is the Magic Maps website which hosts an interactive map originated from Ordnance Survey data.  This map has many spot heights not on other publicly available Ordnance Survey maps and for this hill a 283m spot height is given on the area of its summit. 

Extract from the Magic Maps website

The details for this hill were also re-assessed against the mapping on the OS Maps website.  This is the replacement for OS Get-a-map and until recent times had contours at 5m intervals which were proving consistently more accurate compared to the 5m contours that sometimes appear on the Ordnance Survey 1:25,000 Explorer map and used to appear on the online Vector Map Local.  This resulted in its bwlch height being estimated as c 261m based on interpolation of 5m contouring between 260m – 265m. 

The Trimble GeoXH 6000 gathering data at the summit of Castle Hill

However, it was not until LIDAR became available that the details 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.

Therefore, the confirmation of the addition of this hill to 200m Sub-Twmpau status is due to detail on contemporary maps produced from Ordnance Survey data, a Trimble GeoXH 6000 summit survey, and subsequent LIDAR analysis, resulting in a 283.2m summit height and a 258.6m bwlch height, with these values giving this hill an estimated 24.6m of drop, which is sufficient for it to be classified as a 200m Sub-Twmpau.

 

The full details for the hill are: 

Group:  Stiperstones 

Name:  Castle Hill 

OS 1:50,000 map:  137

Summit Height:  283.2m (converted to OSGM15, Trimble GeoXH 6000) 

Summit Grid Reference:  SO 31430 94540 (Trimble GeoXH 6000) 

Bwlch Height:  258.6m (LIDAR) 

Bwlch Grid Reference:  SO 31415 94604 (LIDAR) 

Drop:  24.6m (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

Myrddyn Phillips (March 2021)

 

 

 

 

 

Thursday, 10 December 2020

Mapping Mountains – Trimble Surveys – Stiperstones


31.08.20  Todleth Hill (SO 288 945), Roundton Hill (SO 294 949), Brithdir Hill (SO 298 951), Cefn Top (SO 317 953), Pen y Mirth (SO 319 948) and Castle Hill (SO 314 945)  

Roundton Hill (SO 294 949)

Having visited Corndon and Lan Fawr two days ago, I was enthused with the prospect of visiting their adjacent P30s.  I’d only been on these hills once before in January 2004 and remember them giving a good circuit and outside of the steep sided and popular Roundton Hill, the land is seldom visited by the hill walker.

I was parked and walking up the narrow lane leading through the small community of Hurdley by 8.15am.  A public footpath led up valley between the steepening slopes of Todleth Hill to the west and Roundton Hill to the east.  The valley was still in shade with dew soaked grass heralding the first sign of impending autumn.  Above, the two summits cast colour as the early morning sun spread across their tops from the east.

Approaching Todleth Hill

I followed another public footpath up through a wood toward the higher southerly flank of my first hill of the day; Todleth Hill.  Numerous blackberries tempted me to stop and indulge in breakfast, but I concentrated on reaching the open hillside above and continuing the short distance to the grassed summit area.

Roundton Hill from the ascent of Todleth Hill

Soon the Trimble was set-up atop my rucksack gathering data.  With the offset noted between its internal antenna and the ground at its base, I stood away from the equipment as it gathered its individual datum points and soaked in the scene with the steep south-westerly slopes of Roundton Hill looking particularly daunting.

Gathering data at the summit of Todleth Hill

Once the equipment had gathered and stored its allotted data, I closed it down, packed it away and headed down the grassed northern slopes toward the hill’s connecting bwlch, which is positioned on the narrow lane close to houses in the small community of Old Churchstoke.

All was quiet as I quickly assessed the lay of land, with the hill to hill traverse and valley to valley traverse meeting on the road.  I quickly set the Trimble up and hoped that no passing vehicle would demolish it and my rucksack.  Considering its set-up position it achieved the 0.1m accuracy level before data should be logged remarkably quickly and I patiently waited for five minutes of data to be gathered and stored.  During this all was quiet and thankfully no vehicles appeared.

Gathering data at the bwlch of Todleth Hill

The continuation of the narrow lane first led downhill and then up toward a point that I could access the open hillside to my east which led directly to the bwlch between Roundton Hill and its 1m map heighted higher neighbour of Brithdir Hill.  The bwlch consists of grass and today it had a few sheep nonchalantly munching in the early morning sunshine.

I assessed the lay of land at the bwlch from a number of directions, and having judged where its critical point lay, I set the Trimble up for another five minute data collection.  During which I stood and looked up to Roundton Hill, this hill is impressive with steep sides and a series of small crags with a profile that is easily distinguished from afar.

Gathering data at the bwlch of Roundton Hill

Once the Trimble was packed away I followed the path from the bwlch as it wound its way up to the high point of Roundton Hill.  After setting the Trimble up I walked back down a section of the path and took a series of photos looking out toward Corndon, Lan Fawr and my next hill; Brithdir Hill.  All looked inviting, bathed in delicate morning colour.

Lan Fawr on the left and Corndon on the right from Roundton Hill

After closing the Trimble down I had a quick look at the panoramic viewfinder close to the summit and walked toward the steepening drop to look down on Todleth Hill.  I was surprised that on such a beautiful bank holiday Monday morning no one, except for me, was on the hill.  However, the solitude and view were to be savoured.

Todleth Hill from Roundton Hill

I doubled back for my next hill, over the bwlch I had just surveyed and up the continuation of a green track bi-passing gorse on the way.  The summit of Brithdir Hill consists of an attractive small embedded rock.  The Trimble was soon set-up aligned with its high point gathering data.

Gathering data at the summit of Brithdir Hill

My onward route now took me across country via Barry Llewelyn at Brithdir Farm.  This farm is directly below the summit I had just Trimbled and soon I was rounding the corner toward its front gate, at the same time Barry was walking down the path toward the gate, our unexpected meeting made us both jump.

Barry’s family have farmed from Brithdir since the 1860s and he named many of the hills in the surrounding area, including Cefn Top which he rents, and which was my next hill on the walk.  I spent a number of minutes with Barry and enjoyed our time together.  Thanking him for his time I headed down the farm’s access track on to another narrow lane which took me all the way to the next bwlch, which connects with Cefn Top.

Barry Llewelyn at Brithdir farm

This bwlch is positioned just off the narrow lane through a gate and close to another, with copious amounts of nettles close by.  As the Trimble gathered its allotted data I stood close to a tree and felt the morning’s exertions starting to catch up with me.

Brithdir Hill from the approach to Cefn Top

The summit of Cefn Top was close by, and a green track led through a gate close to where I had accessed its bwlch, and from here up toward its summit.  The Tithe map names the upper field as Long Top, an apt name, as from the direction I approached; the upper part of the hill has a long flattish top.  I took two data sets, with the second my favoured position for its summit.

Gathering data at the summit of Cefn Top with Corndon in the background

Leaving the summit dappled cloud cast shadow across the hills; flashes of late summer colour accentuated the shadowed parts of hillside.  It was a joy to be out on such a day.  Quietness pervaded the land.  However, what I encountered at the next bwlch broke any semblance of peacefulness. 

The next bwlch connected with the penultimate hill of the day, with an earthen track leading across a field, where a friendly herd of grazing cows showed interesting in my surveying activities.  They heralded my arrival with a chorus of extremely loud mooing, with one cow after another giving voice.  This reverberated around an otherwise quiet and isolated spot for many minutes.  During data collection I sat under a tree and smiled at the scene.

Gathering data at the bwlch area of Pen y Mirth

A slow plod uphill led me to the next summit which is crowned by a field boundary and a misshapen Ash tree.  I set the Trimble up directly over the high point on top of a fence post and waited for the 0.1m accuracy level to be achieved.  This position was enclosed and directly under the tree.  I decided after waiting for about 20 minutes to reposition the equipment on a part of the tree, and proceeded to gather data. 

At the summit of Pen y Mirth

My onward route took me down across a large field on to a track leading through forestry to the lane beside Yew Tree Farm, where I called and chatted with the farmer for 15 minutes or so.

I had one hill left to visit, and the farmer at Yew Tree Farm directed me to the best route toward it.  This hill is named Castle Hill and consists of an old Motte and Bailey.  I took two data sets from its summit area, sitting during both, relaxing in the quiet surrounds and tempted by more blackberries.

Gathering data at the summit of Castle Hill

I considered surveying Castle Hill’s connecting bwlch, but on inspection the field where I judged it to be positioned had a large herd of cows in it.  Happy with just the summit having been surveyed I headed down the steep sides of the upper hill to the Church below and the lane next to it, toward a series of footpaths leading me back toward Hurdley.

I suffered on the way back, partly through the warmth of the afternoon, but also because some of the footpaths did not seem to exist on the ground and therefore I spent much of the time wandering through thick grassed fields aiming toward where I thought I should be going.

Eventually I reached the small community of Hurdley and a few minutes later, my car, having been on the hill for over eight hours, with eleven surveys completed, six hills visited and another local name; Cefn Top, documented. 

LIDAR image of Castle Hill (SO 314 945)


Postscript 

Since visiting 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 being prioritised for some of these hills.


Survey Result:


Todleth Hill 
 
Summit Height:  310.7m (converted to OSGM15)

Summit Grid Reference:  SO 28890 94518

Bwlch Height:  246.5m (converted to OSGM15)

Bwlch Grid Reference:  SO 28828 95012

Drop:  64.2m

Dominance:  20.65%





Roundton Hill 
 
Summit Height:  370.4m (converted to OSGM15)

Summit Grid Reference:  SO 29408 94952

Bwlch Height:  327.0m (converted to OSGM15)

Bwlch Grid Reference:  SO 29531 95067

Drop:  43.4m

Dominance:  11.72%





 
Summit Height:  371.1m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SO 29863 95157 (Trimble GeoXH 6000)

Bwlch Height:  312.8m (LIDAR)

Bwlch Grid Reference:  SO 29966 95737 (LIDAR)

Drop:  58.4m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  15.73% (Trimble GeoXH 6000 summit and LIDAR bwlch)





 
Summit Height:  354.4m (converted to OSGM15)

Summit Grid Reference:  SO 31764 95334

Bwlch Height:  313.2m (converted to OSGM15)

Bwlch Grid Reference:  SO 31502 95512

Drop:  41.2m

Dominance:  11.62%





 
Summit Height:  332.2m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SO 31947 94840 (Trimble GeoXH 6000)

Bwlch Height:  299.4m (LIDAR)

Bwlch Grid Reference:  SO 31822 94926 & SO 31827 94935 (LIDAR)

Drop:  32.7m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  9.86% (Trimble GeoXH 6000 summit and LIDAR bwlch)





Castle Hill 
 
Summit Height:  283.2m (converted to OSGM15, Trimble GeoXH 6000) (significant height revision)

Summit Grid Reference:  SO 31430 94540 (Trimble GeoXH 6000)

Bwlch Height:  258.6m (LIDAR)

Bwlch Grid Reference:  SO 31415 94604 (LIDAR)

Drop:  24.6m (Trimble GeoXH 6000 summit and LIDAR bwlch) (200m Sub-Twmpau addition)

Dominance:  8.70% (Trimble GeoXH 6000 summit and LIDAR bwlch)