Mapping Mountains – Trimble Surveys – Mynydd Hiraethog

 

26.02.22  Gogarth (SH 767 833, previously Trimbled) 

Gogarth is one of the Welsh terms for what many refer to as the Great Orme.  This is the up thrust of land that forms a limestone promontory overlooking the salubrious domain of Llandudno to its south-east and the environs of the north Wales coast in all other directions. 

Gogarth (SH 767 833)

The hill is not substantive in height, but is in its dominance, as it is connected to the mainland by a bwlch which LIDAR gives as 5.4m in height.  The area of the bwlch has undergone substantial terra forming; therefore the natural height could be lower. 

The summit of Gogarth was Trimbled on the 31^st December 2013 and was the sixteen P30 I had surveyed with this equipment.  The day was particularly chilly when the summit was surveyed, albeit with a spotless blue sky and to my knowledge this was the first time I had visited this hill, unless I had a prior visit with my parents when I was very young. 

Having Trimbled its summit and LIDARed its bwlch, I had no plan on re-visiting.  However, as I was at my brother’s for the weekend and with a good forecast for Saturday, albeit still with a definite chilled feel to the weather, we headed out for a road trip and found ourselves on the A55 heading east toward Llandudno.  Once the prospect of visiting the summit of Gogarth was mentioned it was all too easy to head its way and join the one way toll road heading around its eastern periphery, which gives access up a zig-zagged steep road to the complex of buildings surrounding its summit. 

LIDAR bwlch image of Gogarth (SH 767 833)

This visit was so unplanned I didn’t even bring my camera, so the photos accompanying this post are from previous walks.  The toll road costs £3.50 if memory serves me right (I grabbed a note and waited for change).  The road then heads around the eastern side of the hill with views out and across the sea, a left hand two way road then heads up.  We took this and parked at the top. From here it is only a short walk to the triangulation pillar which adorns the summit, with the high point of the hill a nobbled rock close to the trig pillar. 

The Trimble GeoXH 6000 gathering data at the summit of Gogarth

It was gusty on top with a multitude of people appearing from all directions.  It seemed everyone was here enjoying the blue skied sunny early afternoon.  We left the summit after five minutes and wandered back to the car before continuing down the steep road and the one way system now around the northern and westerly part of the hill. 

It was an unexpected visit and one that encouraged me to check LIDAR for the bwlch height and position of this hill.  Gogarth is a fine hill and one whose convenient road makes for an easy ascent if so inclined. 

 

Survey Result: 

 

Gogarth (significant name change)

Summit Height:  207.1m (converted to OSGM15, from previous Trimble GeoXH 6000)

Summit Grid Reference:  SH 76749 83334 (from previous Trimble GeoXH 6000)

Bwlch Height:  5.4m (LIDAR)

Bwlch Grid Reference:  SH 82244 78704 (LIDAR)

Drop:  201.7m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  97.41% (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

 

For details on the summit survey of Gogarth

For further details please consult the Trimble Survey Spreadsheet

 

 

 

 

 

 

Mapping Mountains – Trimble Surveys – Mynydd Hiraethog

18.09.19  Foel Uchaf (SJ 046 590, only bwlch surveyed)

At least this bwlch survey would give me a semblance of a walk, however short in time and distance.  As the day consisted of roadside bwlch surveys I was by now used to pulling my car up at a convenient parking place and sauntering a few metres either to the position of the bwlch, or putting the Trimble on the roof of my car with it positioned directly over where I judged the respective bwlch to be positioned.  But the surveying of this bwlch entailed a walk down a road and in to a field which brought a semblance of exercise to the day’s proceedings.

The bwlch of Foel Uchaf

This survey formed a part of a roadside bwlch surveying trip and was squeezed between the bwlch surveys of Moel Yta and Moel Fama and was the seventh of nine such surveys planned for the day.

I’d already driven a digitised Google car on the minor lane to the north-west of this hill’s summit and found a convenient place to park, and 24 hours later I was there, safely parked with rucksack on my shoulders and Trimble in hand walking down the continuation of the minor road to a gate that gave access in to the field where one of the options for this hill’s bwlch is positioned.

The field is used for grazing sheep and a few sauntered around munching away as I made my way to what proved to be a relatively tight bwlch that was easy to pinpoint as I assessed the lay of land, and within a few minutes the Trimble was in position atop my rucksack gathering allotted data.

Gathering data at the bwlch of Foel Uchaf

The 5m contours on the OS Maps website indicate that another positional option for the bwlch is situated further west from the favoured position where the Trimble was now gathering data from.  Therefore, once data were stored I closed the equipment down and headed to the westerly perimeter of the field to the boundary hedge where a second data set was gathered.  This second position was adjacent to the minor road that heads south toward the Afon Clywedog. 

For the second data set I placed the Trimble on a fence post and noted the measurement offset, however this placement was above the adjacent road, which after the survey I visited and took another measurement to the approximate position of the ground at the base of the fence post.

Gathering data at the second bwlch set-up position

I then visited the field on the other side of the minor road and as this was on the hill to hill traverse and looked level if not slightly lower than the road, I took a third data set with the Trimble set up beside a track leading westward around the southern confines of Moel Yta.

Gathering data at the third bwlch set-up position

Once data were stored I made my way back to the car, checked the map and headed toward Rhuthun (Ruthin) and the continuation on the A525 road to the penultimate bwlch survey of the day; that for Moel Fama. 

Survey Result:

Foel Uchaf

Summit Height:  372m (spot height)

Summit Grid Reference:  SJ 04697 59012 (hand-held GPS via DoBIH)

Bwlch Height:  285.7m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SJ 03828 59515 (Trimble GeoXH 6000)

Drop:  86m (spot height summit and Trimble GeoXH 6000 bwlch)

Dominance:  23.20% (spot height summit and Trimble GeoXH 6000 bwlch)

   

For further details please consult the Trimble Survey Spreadsheet

Mapping Mountains – Trimble Surveys – Mynydd Hiraethog

18.09.19  Moel Yta (SJ 028 598, only bwlch surveyed)

The bwlch of Moel Yta was the sixth of nine planned surveys of the day, all where bylchau, and all either on or beside roads.  The Moel Yta bwlch is positioned to the west of its summit and inspection via a digitised Google car implied that its critical point was on the grass verge besides a meeting of minor roads, and I hoped my car could be squeezed off of the minor road leaving sufficient space for any passing vehicle.

The bwlch of Moel Yta

I approached the bwlch from the north having just surveyed the bwlch of Foel Gasyth and was met with a Road Closed sign, as it also said Except for Access, and as I wanted access, I continued.

Arriving at the diagonal cross road which constitutes the bwlch I knew I had to work fast as it seemed the road was closed for access to the near wind farm.  Thankfully the rough grass verge where inspection with the digitised Google car suggested the critical point to be situated was wide enough to pull my car on to.  I quickly got out, inspected the lay of land and jumped back in to my car to re-position it a few metres to where the Trimble atop its roof would be aligned with where I judged the critical point of the bwlch to be placed.

The Trimble set-up position at the bwlch of Moel Yta

Having set the Trimble up I stood away from the equipment as it gathered its all-important data and hoped that a large lorry would not appear and disrupt satellite reception.  None did.

Gathering data at the bwlch of Moel Yta

Roadside bwlch surveying was proving fun, although it requires a lot of research if wanting to do a number of surveys during the day.  Although bwlch surveying is fun I needed to move on as soon as the Trimble had gathered its allotted data, and once closed down and packed away this is exactly what I did with the eastern bound minor road leading toward my next bwlch survey which connects to the 372m map heighted summit of Foel Uchaf.

Survey Result:

Moel Yta

Summit Height:  404m (spot height)

Summit Grid Reference:  SJ 02836 59890 (hand-held GPS via DoBIH)

Bwlch Height:  353.3m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SJ 01883 60114 (Trimble GeoXH 6000)

Drop:  51m (spot height summit and Trimble GeoXH 6000 summit)

Dominance:  12.55% (spot height summit and Trimble GeoXH 6000 summit)

  

For further details please consult the Trimble Survey Spreadsheet

Mapping Mountains – Trimble Surveys – Mynydd Hiraethog

18.09.19  Foel Gasyth (SJ 022 622, only bwlch surveyed)

The bwlch of Foel Gasyth is positioned approximately 1km southward from its summit.  The 5m contouring on the OS Maps website and a digitised inspection in a Google car suggested that there are two points that vie for the critical point of this bwlch.  The first is adjacent to B4501 road as it makes its way north-eastward toward the town of Dinbych (Denbigh) and the second is in an adjacent field.  I hoped to survey both.

LIDAR summit image of Foel Gasyth (SJ 022 622)

It was just past midday when I pulled my car up adjacent to a gate close to the high point of this part of the B road.  The conditions remained becalmed with in the main blue sky, although a bank of high milky cloud was pushing in from the north.  Except for a rogue lorry and an occasional vintage car the B road remained quiet, as did the surrounds, which for the purpose of my visit was ideal.

The Trimble set-up position at the first option for the bwlch of Foel Gasyth

After a quick inspection of the lay of the land at this point of the road I repositioned my car aligning its roof with the high point of the road.  And once the Trimble was in place on the car roof I measured the offset between its internal antenna and the ground at its base, clambered on top of the surveying steps, created the file in the equipment and waited for the 0.1m accuracy level to be attained before data should be logged, and once attained press ‘Log’ and walked a short distance away so as not to interfere with satellite reception.  The Trimble happily beeped away gathering its individual datum points whilst I scribbled all necessary detail in my note book, took a few photos and once the allotted data were gathered and stored, clambered back on to the surveying steps and pressed ‘Done’.

Gathering data at the first option for the bwlch of Foel Gasyth

I then repositioned my car around the corner of the near cross roads on the widest part of a minor road and walked back to the gate where I originally parked.  The gate gave easy access in to the adjacent field where map contouring implies that a second option for the critical point of this bwlch is positioned.

The interpolated ten figure grid reference led me toward the area of the bwlch, I then assessed the lay of land and chose the spot for Trimble placement.  During data collection a few sheep inquisitively approached before heading back across the wide expanse of the field.

Gathering data at the bwlch of Foel Gasyth

Again, all remained quiet as the Trimble gathered its allotted data; it was as if the whole land was asleep, in a slumber dulled by the sun.  Once five minutes of data were gathered and stored I closed the Trimble down, packed it away and made my exit from the field back to my awaiting car.  Next stop the bwlch of Moel Yta. 

Survey Result:

Foel Gasyth

Summit Height:  377.6m (LIDAR)

Summit Grid Reference:  SJ 02245 62236 (LIDAR)

Bwlch Height:  282.2m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SJ 02055 61204 (Trimble GeoXH 6000)

Drop:  95.4m (LIDAR summit and Trimble GeoXH 6000 bwlch)

Dominance:  25.26% (LIDAR summit and Trimble GeoXH 6000 bwlch)

  

For further details please consult the Trimble Survey Spreadsheet

Mapping Mountains – Trimble Surveys – Mynydd Hiraethog

18.09.19  Moel Fechan (SH 993 632, only bwlch surveyed)

This was the fourth of nine planned roadside bwlch surveys during the day and each had either been LIDARed, examined in detail via 5m contouring on the OS Maps website or driven to and over in a digitised Google car assessing the lay of land and the ups and downs of the hill to hill and valley to valley traverses.

The bwlch of Moel Fechan

As LIDAR does not cover the area of this hill’s summit or connecting bwlch I was reliant upon map contours and the Google car for pre-visit assessment, and then an on-site inspection when there.

The ‘there’ part was a grass verge beside the A543 road close to a cross roads intersecting with the B5435 and a minor road.  I’d already found a parking place via driving the Google car and was soon loading up with all necessary equipment including my newly purchased surveying steps which are ideal for car roof surveys as they give height to see the screen to create the file necessary to start gathering data.  They are also ideal for grass verge roadside surveying as they give the Trimble an added semblance of protection when balanced on top of my rucksack and importantly a higher position which enhances satellite reception.

The set-up position at the bwlch of Moel Fechan

As I approached the cross roads and turned right on the B5435 to park in a pull in place close to a gate, a tractor with attached hedge cutting equipment was parked nearby.  Leaving my car I walked the short distance up the A543 to where I judged the critical point of the bwlch to be positioned.  As I did so the tractor started chugging up the road conveniently cutting the grass verge where I was just about to set the equipment up.  I flagged the tractor down and quickly explained what I wanted to do, the driver said he wouldn’t be heading back up the road for 15 minutes or so, which was all I needed, and once the grass was cropped I unfolded the surveying steps and positioned my rucksack on top with the Trimble placed atop the latter; giving a measurement offset of 0.95m between its internal antenna and the ground below.

Gathering data at the bwlch of Moel Fechan

A few vehicles zoomed past as the Trimble beeped away gathering data.  During data gathering I stood beside the road 50 metres or so from the equipment and waited for the allotted data to be gathered and stored.

I left the Trimble gathering data for six minutes and then closed it down happy in the knowledge that another bwlch survey was complete.  All that remained was to pack the Trimble away, fold the steps up and walk the short distance back to my car.  Next stop the bwlch connecting to Foel Gasyth.

Survey Result:

Moel Fechan

Summit Height:  372m (spot height)

Summit Grid Reference:  SH 99335 63247 (hand-held GPS via DoBIH)

Bwlch Height:  299.2m (converted to OSGM15, Trimble GeoXH 6000)

Bwlch Grid Reference:  SH 98493 63393 (Trimble GeoXH 6000)

Drop:  73m (spot height summit and Trimble GeoXH 6000 bwlch)

Dominance:  19.56% (spot height summit and Trimble GeoXH 6000 bwlch)

  

For further details please consult the Trimble Survey Spreadsheet

Mapping Mountains – Trimble Surveys – Mynydd Hiraethog

18.09.19  Bryn Trillyn (SH 947 590, only bwlch surveyed)

The connecting bwlch of Bryn Trillyn is in utter contrast to its summit.  The latter is heather bound with moor grass and extensive views toward the higher Eryri hills, whilst its bwlch is in a field next to the A543 road at it speeds its way from the outskirts of Pentrefoelas toward Dinbych (Denbigh) in the north-east.

The summit of Bryn Trillyn (SH 947 590)

I’d last visited its summit along with Mark Trengove; watching the sunset from its high point as a thin flash of yellowed light highlighted an otherwise deep and darkening blued sky.

Weather and time of day can dictate many aspects of hill walking, and especially for those related to emotive state, and where the summit had been otherworldly with purpled heather and stillness of the setting sun, my visit to the bwlch consisted of greened fields and an occasional passing vehicle, with middays warmth leaving a contented feeling, but one mainly based on a good job done, as I needed to gather two sets of data, one from either side of the road where the hill to hill traverse descended to a slightly raised strip of tarmac, leaving a low point in each opposing field.

I’d examined the lay of land of this bwlch via the digitised image in a Google car and found a convenient parking place and realised before visiting that a point in the field either side of the road would need surveying.  Therefore, as I left my car I had a quick look on both sides of the road and decided that as the digitised image suggested; two data sets were required.

The Trimble was soon set-up atop my rucksack gathering data on the eastern side of the road.  Its placement was relatively easy to pinpoint as a greened and grassed small and broad ridge descended to the boundary fence, and once data were gathered and stored I closed the equipment down and headed back to the road and the field on its other side.

Gathering data at the bwlch of Bryn Trillyn

The point to survey on the western side of the road was much tighter and in a dip close to the boundary fence, and as the Trimble beeped away collecting its individual datum points I happily stood back in the sunshine content that this third bwlch survey of the day was nearing completion, but with another six planned I could not linger. 

Gathering data at the second option for the bwlch of Bryn Trillyn

So, once the allotted data were gathered and stored I packed the equipment away and headed back the short distance to my car, checked the map and continued north-east toward the bwlch of Moel Fechan.

Survey Result:

Bryn Trillyn

Summit Height:  496.4m (converted to OSGM15, from previous Trimble GeoXH 6000 survey)

Summit Grid Reference:  SH 94748 59094 (from previous Trimble GeoXH 6000 survey)

Bwlch Height:  446.5m (converted to OSGM15)

Bwlch Grid Reference:  SH 96287 59668

Drop:  49.9m

Dominance:  10.05%

  

For details on the summit survey of Bryn Trillyn

For further details please consult the Trimble Survey Spreadsheet

Mapping Mountains – Trimble Surveys – Mynydd Hiraethog

18.09.19  Pen yr Orsedd (SH 892 555), only bwlch surveyed

Pen yr Orsedd is a fine unassuming hill with its high point consisting of a few rogue embedded rocks amongst its grassland moored summit.  The last time I visited was in June 2014 with Mark Trengove and Aled Williams.  As the Trimble gathered its customary summit data we lazed in the sun with Llyn Alwen forming a majestic backdrop.

Gathering data at the summit of Pen yr Orsedd (SH 892 555)

Since the summit survey the 5m contouring on the OS Maps website has become available and this is proving an excellent resource when checking on height values and their placement, and in the main, is proving more accurate compared to the standard contouring on Ordnance Survey 1:25,000 Explorer maps. 

The summit height produced by the Trimble GeoXH 6000 for Pen yr Orsedd is 442.211m and with an estimated bwlch height of c 409m based on contouring between 400m – 410m it meant that this hill was relatively safe as a Pedwar with an estimated c 33m of drop.  However, the 5m bwlch contours on the OS Maps website is between 410m – 415m with interpolation giving an estimated bwlch height of c 412m, with this value giving the hill an estimated c 30m of drop, which is the minimum drop value for Pedwar status.  Therefore the bwlch needed to be surveyed and given an accurate height.

The bwlch of Pen yr Orsedd is positioned close to the A543 road as it makes its way north-eastward from the outskirts of Pentrefoelas toward Dinbych (Denbigh).  Google maps indicated I could park at the entrance to a small disused quarry a couple of hundred metres from where a gate gives access down to the area of the bwlch.  Having parked I walked the short distance to the gate where there is now a long flat gravelled area beside the road with sufficient space for a number of cars to be parked.

The bwlch looked relatively inviting with beige tinged moor grass predominating, interspersed with occasional rogue tussocks.  Leading from the gate was a sheep path and a line of vehicle tracks on the moored grass.

The bwlch of Pen yr Orsedd

I was soon at the area of the bwlch and the sheep path crossed directly over it, although contour interpolation placed its critical point slightly to the north.  Having deposited my rucksack on where I judged the bwlch to be positioned, I walked a short distance up the opposing hillside to look down on it from a different viewpoint.  I then contoured to the south and decided that my rucksack was placed at its critical point.

Sauntering back to the bwlch I aligned the placement of the Trimble atop my rucksack with the critical point of the bwlch and set it to gather data.  During data gathering I again ventured up the opposing hillside and decided that I should take a second data set from just south of the equipment’s current position.

Gathering data at the bwlch of Pen yr Orsedd

Whilst the Trimble quietly beeped away gathering its individual datum points I took a series of photos with a succulent yellowed moor as foreground and the great mass of sun drenched Yr Wyddfa floating above all surrounds as backdrop.

Yr Wyddfa floating above the moor

Once the allotted data were gathered and stored I headed a short distance southward and positioned the Trimble again atop my rucksack to give it elevation above its immediate surrounds.  This time it was placed directly on top of one of many impressive rounded green grassed tussocks beside the start of a bogged water course that indicated this placement to be lower than the first, which agreed with my visual inspection.

The set-up position for the second data set at the area of the bwlch of Pen yr Orsedd

Bwlch surveying was proving very enjoyable.  It is much easier than summit surveying and especially so if positioned beside a road.  This bwlch proved another wonderful place with just the occasional sheep as company, the bwlch just sat there, seldom visited and giving tranquillity to an otherwise busied scene with the main road being so close. 

Once the allotted data were gathered from the impressive greened grassed tussock I packed the Trimble away and walked the short distance back to my car, checked the map and headed further north-east to the next bwlch, which connects to the Pedwar of Bryn Trillyn.

Survey Result:

Pen yr Orsedd

Summit Height:  442.2m (converted to OSGM15, from previous Trimble GeoXH 6000 survey)

Summit Grid Reference:  SH 89294 55542 (from previous Trimble GeoXH 6000 survey)

Bwlch Height:  409.2m (converted to OSGM15)

Bwlch Grid Reference:  SH 90076 55064

Drop:  33.0m

Dominance:  7.47%

For details on the summit survey of Pen yr Orsedd

  

For further details please consult the Trimble Survey Spreadsheet