Mapping Mountains – Significant Height Revisions – 200m Twmpau

Winllan Hill (SJ 217 214)  

There has been a Significant Height Revision to a hill that is listed in the 200m Twmpau initiated by a survey with the Trimble GeoXH 6000, with these details being retrospective as the survey that resulted in this height revision was conducted over two days; 28^th / 29^th August 2015.

The listing that this height revision affects is:

200m Twmpau - These are the Welsh hills at or above 200m and below 300m in height that have a minimum drop of 30m.  The word Twmpau is an acronym for thirty welsh metre prominences and upward.

The name of the hill is Winllan Hill and it is situated in the lower easterly hills of Y Berwyn, and is positioned above Llansanffraid-ym-Mechain which is situated beside where the Afon Cain flows in to the Afon Efyrnwy (River Vyrnwy).  The hill was initially surveyed in the late evening in the company of Mark Trengove after nourishing our appetite in the Bradford Arms in Llanymynech.

Access to Winllan Hill is good as public footpaths from the south, west, north and east head towards its summit and parking is easily found when approaching the hill from the west and north, this is also likely to be the case if approaching the hill from the east and south.  The high point of the hill is beside a fence and under a large overhanging tree, and is only a few metres from where a public footpath crosses the field that the summit is situated in.

Prior to the survey with the Trimble GeoXH 6000 the hill was listed as 216m high based on the spot height on the area of the summit that appears on the Ordnance Survey 1:25,000 Explorer map, and an estimated drop value of c 48m, based on bwlch contour interpolation which gives the height of the bwlch as c 168m.  However, there is significantly higher land to the north of where the 216m spot height is positioned on the ground.  With the height resulting from the survey of the summit with the Trimble GeoXH 6000 being 220.3m (converted to OSGM15).  

Therefore this hill’s new summit height is 220.3m (converted to OSGM15) which is 4.3m higher than the previously listed height of 216m which was based on the Ordnance Survey 1:25,000 Explorer map spot height.

The full details for the hill are:

Cardinal Hill:  Rhialgwm

Summit Height (New Height):  220.3m (converted to OSGM15)

Name:  Winllan Hill

OS 1:50,000 map:  126

Summit Grid Reference:  SJ 21709 21460 

 

Drop:  c 52m

Gathering data from the summit of Winllan Hill which resulted in this hill's significant height revision

For details on the 1st survey that when combined with the 2nd survey significantly revised the summit height of this hill

For details on the 2nd survey that when combined with the 1st survey significantly revised the summit height of this hill

Myrddyn Phillips (October 2015)

Mapping Mountains – Trimble Surveys – Y Berwyn

29.08.15  Winllan Hill (SJ 217 214)  

Winllan Hill (SJ 217 214)

Having waxed lyrical on yesterday evening’s walk to Winllan Hill I re-visited its summit this morning and took a further five data sets as yesterday’s data, when processed, showed the Estimated Accuracies to be 0.5-1m: 57.49% and the Standard Deviation to be 0.9m.  The detail within this data set is probably the worst the Trimble has produced during the last 21 months.  Perhaps the large overhanging tree at the summit obstructed satellite coverage to a greater degree than I had imagined, or perhaps it was getting too late and the Trimble just needed to go to bed?

As the afternoon’s forecast was for heavy localised showers I wanted a relatively early start and by 9.30am I was back on top of the hill.  On our previous evening’s walk Mark and I had ascended this hill from the west, this morning I parked in a pull-in spot and walked up the paved road / track that leads to Plas Onn and approached this hill from the north.

I knew exactly what I wanted to do and had come well prepared with every available piece of surveying equipment that I possess.  My aim was to gather a number of data sets and to do so in a variety of ways; this at least would give a comprehensive comparison between styles and the heights produced.  At the very least this would give an opportunity for the average of all data sets to be taken as the height for this hill.

When I arrived at the summit I stored the majority of gear beside the base of the large overhanging tree and headed down to where the 216m spot height on current Ordnance Survey maps appears on the ground.  This is situated at or near to a ringed and grassed natural embankment which resembles the remains of an earthen embankment that one would usually associate with an ancient hill fort, but there is no map evidence that one ever existed on this hill. 

Once this point had been identified I set the Trimble up and as it gathered its five minutes of data I assembled my old measuring staff.  Once the data set was complete I closed the Trimble down and left it in situ and proceeded to take a reading at a 4½ ft height level from the land between where the Trimble was placed and where the high point of the hill is situated under the large tree.  By aligning the fixed spirit level on my measuring staff with the base of the Trimble I then turned 180° and took a reading toward the high point of the hill.  Once re-positioned at this point it meant that this ground was approximately at the same height as the position of the Trimble, I then took readings to the summit with the conclusion being that the summit of the hill is approximately 9ft 2″ higher than where the Trimble was placed, which was at or near to where the 216m spot height appears on the ground.

The 1st of the morning's data sets - gathering data from near to where the 216m spot height appears on the ground

I then took a second five minute data set with the Trimble from the same spot, and once complete I repeated the measurement with my old staff but started from the position of the Trimble, this meant a greater horizontal distance for the first 4½ ft vertical height measure, by doing this I would have a comparison of measurements taken with the old staff.  This second measure gave a vertical height gain between the Trimble position and the summit of approximately 8ft 10″ with the average of the two measurements with the old staff being 9ft.

The 2nd of the morning's data sets - with the Trimble just evident on the top of the grassy mound to the right and the much higher summit of the hill on the left

I now wanted to try and get another data set from the high point, whereas the Trimble was set up on top of my rucksack the previous evening with a 0.43m measurement offset recorded, I now positioned the Trimble on the improvised Tupperware tripod which elevated its internal antenna by 0.18m above the ground.

During this data collection I stood behind the large tree out of view of the Trimble and only went out into the field to encourage sheep to graze in another part of the field, as they were slowly encroaching westward toward where the Trimble was now gathering data. 

The 3rd of the morning's data sets - with the Trimble at the summit set up on its improvised Tupperware tripod

Once this third morning’s data set was complete I switched the equipment off and grabbed my measuring staff as this time I wanted a data set with the Trimble positioned 4½ ft below the summit of the hill which would probably give it a greater chance of achieving a good data set.  I proceeded to take readings at a 4½ ft height level until I had aligned the spirit level with the high point of the hill, I then positioned the Trimble on top of my rucksack and measured a 0.42m offset.

By now the sky towards The Wrekin away to the east was breaking out into heavy showers, thankfully these were forming behind Cefn Digoll (the Long Moutnain) and were pushed northward into Shropshire, but as I started to sort out the gear for the fifth and last of the morning’s data sets I noticed a large grey patch of sky forming in the Dyffryn Meifod and as this was closer to Winllan Hill, I did not want to linger.

To the east showers were breaking out over The Wrekin

As the Trimble gathered data positioned 4½ ft below the summit and 0.42m above the ground on top of my rucksack I assembled the tripod and fixed the external antenna to its top.  I haven’t used this tripod for a number of months, as it is always more convenient to use the Trimble operating with its internal antenna, but necessity dictated that a variety of surveying methods would give a comprehensive coverage in determining the height of this hill.

The 4th of the morning's data sets - with the Trimble positioned 4½ ft below the summit and on top of my rucksack

Once the fourth morning’s data set was completed I assembled the tripod and Trimble over the high point of the hill and set it to gather data.  The Trimble always looks good when on its tripod and the external antenna was now positioned above the fence which runs east – west adjacent to the high point of Winllan Hill.  However, the large tree was overhanging the position of the tripod so it’ll be interesting to compare this data set with the others.

The Trimble connected to its external antenna at the summit of Winllan Hill

The 5th and last of the morning's data sets - with the Trimble attached to its external antenna and positioned on its tripod

As I closed the Trimble down after it had stored the last of its data the showers that had started to appear were still being pushed down into Shropshire away to my east, and patches of sunshine were now breaking out around me.  Once all my gear had been checked and packed away I retraced my steps back down the hill and headed home.

The view south-west from the summit of Winllan Hill

Survey Result:

Winllan Hill

Summit Height:  220.3m (average of six surveys and converted to OSGM15) (significant height revision)

Summit Grid Reference:  SJ 21709 21460 (summit relocation confirmed)

Drop:  c 52m

Dominance:  23.61%



For details of the first summit survey of Winllan Hill

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

Mapping Mountains – Summit Relocations – 200m Twmpau

Winllan Hill (SJ 217 214)  

There has been a Summit Relocation to the 200m Twmpau (thirty welsh metre prominences and upward) due to a survey with the Trimble GeoXH 6000, with the following details being retrospective as the survey that resulted in this summit relocation was conducted over two days; on 28^{th /} 29^th  August 2015.

The first of this hill's two surveys was conducted in the company of Mark Trengove on the lower easterly hills of the Y Berwyn, above the small community of Llansanffraid-ym-Mechain which is situated just north-west of where the Afon Cain flows in to the Afon Efyrnwy (River Vyrnwy).

Prior to the survey with the Trimble GeoXH 6000 the hill was listed with an estimated c 48m of drop based on the current Ordnance Survey summit spot height of 216m and an estimated bwlch height of c 168m.

There is good access to the summit of the hill with a number of public footpaths converging on its high point from a variety of directions, with its summit positioned beside a fence and under a large overhanging tree, with the high point only a few metres from where a public footpath crosses the field that it is situated in.

The name of the hill is Winllan Hill and prior to the survey with the Trimble GeoXH 6000 the position of the summit was listed as that of its 216m spot height which is situated at SJ 21686 21409.  This position is placed on a slight rise which resembles part of an ancient earthen embankment associated with an old hill fort, and although there is evidence of these existing on neighbouring hills there is no evidence on current maps that one existed on Winllan Hill.

The position of the relocated summit is at SJ 21709 21460 and this is the top of a field with the high point situated under a large overhanging tree beside a fence that runs in an east – west direction over the summit.  This position is not given a spot height on current Ordnance Survey maps but the survey result produced with the Trimble gave it as 4.3m higher when compared to the position where the 216m spot height appears on current Ordnance Survey maps and approximately 50 metres northward from it.

 

The full details for the hill are:

Cardinal Hill:  Rhialgwm

Summit Height:  220.3m (converted to OSGM15)

Name:  Winllan Hill

OS 1:50,000 map:  126

Summit Grid Reference (New Position):  SJ 21709 21460

  

Drop:  c 52m

The Trimble GeoXH 6000 gathering data at the new summit position of Winllan Hill, with Mark (wearing blue top) standing on the old position of the summit in the left background of this photograph

For details on the survey that relocated the summit of this hill please click {here}

Myrddyn Phillips (August 2015)

Mapping Mountains – Trimble Surveys – Y Berwyn

28.08.15  Winllan Hill (SJ 217 214)  

The contentment and good memories left after a walk can sometimes match the afterglow of colour when the sun sinks ever deeper into a darkened sky and delicate cloud banks enhance the radiant and subtly rich colour.

These feelings of afterglow are hard to quantify, but the essence of contentment and the pervading feelings of happiness from being out on the hill and the after effects must be associated with some form of euphoric experience, when mind and body meet as one in an environment that gives so much beauty to one’s life.

On our way to the summit of Winllan Hill

This hill experience can be found in so many varieties from the adrenalin rush of a scramble to the gentleness of watching the sun set.  Although vastly different they are intrinsically linked.

Part of this beauty is being on the hill in the evening when life slows and the land quietens, this experience and its enthralling aspect is relatively new for me as I am more an early morning hill person when the heat of the day dictates that height should be gained before it overbears the mind and the body.

Evening light on the high Berwyn

These evening walks have become part of my hill routine and they are due to meeting Mark Trengove, and over the last couple of years they have become part of my hill experience and ones that I look forward to immensely.

Sun setting on another day

Much of this is down to enjoying Mark’s company, and the refined dining and good grub associated with these evening walks.  But this enjoyment goes deeper as these evening walks can also mean the gentleness of colour when the sky blazes and glitters the view with a multitude of subtlety. 

Cloud banks at dusk

These beautiful and radiant colour washes only last for brief moments and they should be savoured and breathed in as their experience is one that quickly fades when the sun sinks out of view and the rich colour quickly dissipates to dusk and then darkness.

Gathering data from the summit of Winllan Hill

All too soon it is over, once there and glimpsed and then gone, hopefully to be experienced when another evening walk takes place.  But some of this joy is the not knowing part, will the sun and sky give its subtle and radiant show or will it ebb distant and disappear from view without its blast giving afterglow.

A partly shrouded silken moon over The Wrekin

This evening was one of those occasions when for a few minutes the sky shone and the cloud illuminated the colour with silvery sheen and gentle mauves dissipating itself against the darkened and silhouetted land.

And at the end of the day...........

Those few moments were rather magical and have lasted with me as I write this, as they have left a pleasant feeling of contentment when mind, body, sky and colour seemed to be one.

Survey Result:

Winllan Hill

Summit Height:  220.3m (average of six surveys and converted to OSGM15) (significant height revision)

Summit Grid Reference:  SJ 21709 21460 (summit relocation confirmed)

Drop:  c 52m

Dominance:  23.61%




For details of the second summit survey of Winllan Hill

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