Showing posts with label Allt y Moch. Show all posts
Showing posts with label Allt y Moch. Show all posts

Sunday, 7 February 2021

Mapping Mountains – Trimble Surveys – Hirddywel

 

18.10.20  Y Foel (SO 018 840) and Allt y Moch (SO 022 849) 

Y Foel (SO 018 840)

I’d visited Allt y Moch as one of three walks after lock-down restrictions were lifted in early July.  I’d previously surveyed the hill with my old basic levelling staff as having approximately 29.4m of drop; and as the Trimble result came to 29.98m of drop it was time to re-visit and concentrate on the area of the hill’s bwlch and take further readings from its summit. 

When the Trimble result was sent to Aled he suggested we could combine the re-survey with a visit to Y Foel which is positioned across the intervening small stream valley, with each hill visited from the convenience of a relatively high parking place as a there and back walk. 

The day’s forecast was relatively good with dry conditions and little breeze, and although the day proved to have grey skies the cloud base was above the tops.  We met in Caersŵs and I drove the remaining distance to the hill and parked on a grass verge beside the track that leads down to the old farm house of Foel-Fawr. 

Heading toward Y Foel

Y Foel is a great lump of a forested hill which if not for the conifers would no doubt give excellent views.  Reaching the old farm house which is now no more than a ruin we headed on the continuation of the track in to the conifers.  From the track there are a number of options to head up on forest breaks toward a narrow path that follows this hill’s north-westerly ridge all the way to the summit.  This is the route that Charlie Leventon and I used on my only previous ascent in September 2011. 

We followed one of the rides steeply up to a forest break and after a quick investigation found the ridge path.  This simplified matters as all we now had to do was follow it up until the summit was reached. 

The forest break leading toward the ridge path

Walking on a path through a forest can have its own beauty, in some ways this is similar to walking in mist as few views can be seen and one’s world is suddenly condensed to the immediate surrounds.  It was no different today and as height was gained we started to look out for the small cairn beside the path that constitutes the summit position. 

The ridge path leading toward the summit

We reached what we thought was the summit, but could not see the cairn, therefore we continued in the same direction to make sure that all ground now went downhill, it did, so we headed back to the high part of the hill.  We chose a spot for Trimble placement and before setting it up to gather data I used it as a hand-held device and headed in to the trees to find the spot that LIDAR gives for the summit.  The LIDAR placement was about 15 metres in to the conifers and after assessing the ground I headed back to our preferred high point. 

As I took the measurement offset between the internal antenna and the ground at the base the bottom of the tape hit rock.  This proved to be the small cairn which is now covered in moss and hardly recognisable from what it looked like nine years ago. 

Gathering data at the summit of Y Foel

Prior to setting the Trimble up we headed through one or two conifers to the steep southern flank of the hill which is clear of trees, and sat looking out across the Nant Glyn and beyond to higher hills.  Once back in the trees I set the Trimble to gather data. 

Out of the conifers, the view across the Nant Glyn

Once the allotted data were gathered and stored were reversed our inward route and headed back to where my car was parked, here we met the couple who live at Borth; the small holding just down the narrow lane.  One was sitting on a horse and the other on a quad bike and with their dog happily following they were out for the day.  We chatted for a number of minutes before they headed up the lane. 

Allt yr Moch (SO 022 849)

We now wanted to visit Allt y Moch and followed a green track on the hill’s southern flank which led to the gate at the bwlch.  We knew from the data sets taken on my previous visit where the area of the bwlch is positioned.  However, this is not difficult to ascertain just by eye. 

I’d brought flags in case these were needed and we spent a few minutes deciding how many data sets were to be taken and from where.  Having assessed the lay of land we opted for four data sets, all relatively close together and concentrating on land just to the north of the fence that crosses the bwlch on a hill to hill direction. 

Whilst waiting for the Trimble to achieve its 0.1m accuracy level before data should be logged the conditions progressively got colder, as by now a slight breeze had descended across the bwlch.  However, we persevered and eventually left the bwlch having taken the four data sets that we wanted. 

Gathering data at the bwlch of Allt y Moch

A greened vehicle track leads from the bwlch toward the summit of Allt y Moch and we followed this up to its high point.  On my last visit I’d taken four data sets from the area of the summit with three of these concentrating on its higher ground, and once we had assessed the lay of land and positioned a number of flags, each inserted in the ground to the same level, the flags were then Abneyed and we removed those that were lower, leaving two remaining. 

Gathering data at the summit of Allt y Moch

During data collection we sat on the northern side of the hill out of the breeze and enjoyed the view.  Once the second data set was gathered and stored, I closed the equipment down, packed it away and we headed down following our inward route back to the awaiting car.   

 

Survey Result: 

 

Y Foel  

Summit Height:  435.8m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SO 01864 84066 (Trimble GeoXH 6000)

Bwlch Height:  319m (spot height)

Bwlch Grid Reference:  SO 02299 84267 (spot height)

Drop:  117m (Trimble GeoXH 6000 summit and spot height bwlch)

Dominance:  26.81% (Trimble GeoXH 6000 summit and spot height bwlch)

 

 

Allt y Moch  

Summit Height:  419.7m (converted to OSGM15, from previous Trimble GeoXH 6000 survey)

Summit Grid Reference:  SO 02202 84938 (from previous Trimble GeoXH 6000 survey)

Bwlch Height:  389.6m (converted to OSGM15)

Bwlch Grid Reference:  SO 02366 84827

Drop:  30.1m (400m Sub-Pedwar reclassified to Pedwar)

Dominance:  7.17%

 

 

For details on the first Trimble GeoXH 6000 survey of this hill


For further details please consult the Trimble Survey Spreadsheet

 

 

 

 

 

Saturday, 31 October 2020

Mapping Mountains – Hill Reclassifications – Y Pedwarau – The 400m Hills of Wales

 

Allt y Moch (SO 022 849) – 400m Sub-Pedwar reclassified to Pedwar

There has been a reclassification to the listing of the Y Pedwarau – The 400m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and Aled Williams, which was prompted by detail produced by Joe Nuttall’s summit analysis programme and subsequent evaluation conducted by Ronnie Bowron. 

Allt y Moch (SO 022 849)

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

Y PedwarauThe 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main Y Pedwarau list are five categories of sub hills, with this hill being reclassified from the 400m Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Allt y Moch and it is adjoined to the Pegwn Mawr group of hills which are situated in Mid and West Wales (Region B, Sub-Region B1), and it is positioned with a minor dead end road to its south and the A470 road to its north-west, and has the village of Llandinam towards the north. 

When the original 400m height band of Welsh P30 hills was published on Geoff Crowder’s v-g.me website this hill was included in the accompanying Hills to be surveyed sub list as it had been surveyed using a basic levelling staff by Myrddyn Phillips on the 18th August 2003 as having 96½ft / 29.4m of drop. 

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

The evaluation by Ronnie Bowron of the detail produced by Joe Nuttall’s summit analysis programme prompted this hill’s details to be re-assessed via the mapping on the OS Maps website.  This is the replacement for OS Get-a-map and had contours at 5m intervals which were proving consistently more accurate compared to the 5m contours that sometimes appear on Ordnance Survey 1:25,000 Explorer maps and used to appear on the online Vector Map Local.  The bwlch contours on this mapping were between 385m – 390m, therefore if the 421m summit spot height was accurate it meant this hill had at least 30m of drop and would qualify for Pedwar status.  Because of this it was prioritised for a Trimble GeoXH 6000 survey. 

Allt y Moch was surveyed over two days; 11th July 2020 and 18th October 2020, with seven data sets taken at the area of its bwlch and six data sets taken at the area of its summit, resulting in the hill now being listed with 30.1m of drop. 

The Trimble GeoXH 6000 gathering data at the bwlch of Allt y Moch


The Trimble GeoXH 6000 gathering data at the summit of Allt y Moch

Therefore, the reclassification of this hill from 400m Sub-Pedwar status is due to a Trimble GeoXH 6000 survey resulting in a 419.7m summit height and a 389.6m bwlch height, with these values giving this hill 30.1m of drop, which is sufficient for it to be classified as a Pedwar. 

 

The full details for the hill are:

Group:  Pegwn Mawr 

Name:  Allt y Moch 

OS 1:50,000 map:  136

Summit Height:  419.7m (converted to OSGM15) 

Summit Grid Reference:  SO 02202 84938 

Bwlch Height:  389.6m (converted to OSGM15) 

Bwlch Grid Reference:  SO 02366 84827 

Drop:  30.1m

 

For the additions, reclassifications and deletions to Y Pedwarau – The 400m Hills of Wales reported on Mapping Mountains since the May 2013 publication of the list by Europeaklist please consult the following Change Registers:

 

Y Pedwarau

 

Y Pedwarau – 400m Sub-Pedwarau

 

Y Pedwarau – 390m Sub-Pedwarau

 

Y Pedwarau – 390m Double Sub-Pedwarau

 

Myrddyn Phillips and Aled Williams (October 2020)

  

Monday, 19 October 2020

Mapping Mountains – Trimble Surveys – Hirddywel


11.07.20  Allt y Moch (SO 022 849)  

Allt y Moch (SO 022 849)

In August 2003 I set out with good intention to reach the forested summit of Y Foel (SO 018 840).  After about 45 minutes I emerged out of the trees having had one of those adventures when you’re not sure where you’ve been or where you now are.  I salvaged the day by heading across the intervening valley and finding a forestry track that led me toward Allt y Moch.  I proceeded to survey this hill with my old basic levelling staff and concluded that it had approximately 29.4m of drop.  This method of surveying is only basic, but was responsible for a number of hill reclassifications.  Considering its method many results are accurate, however some aren’t, and this could be one of them as the latest online mapping suggests this hill to be a P30 and therefore I wanted to revisit and survey it with the Trimble GeoXH 6000.

Access to the hill is easy as there’s one or two places to park at the end of a narrow paved road that makes its way uphill toward one of the many access tracks that lead into the western part of the Pegwn Mawr range.  From here it was a short walk on the continuation of the track before taking a branch off on the left that led straight to this hill’s bwlch.

The track leading to the bwlch

I remembered from my last visit that the bwlch had some sort of construction on it, this proved to be a high sided large sheep fold.  Thankfully it wasn’t positioned over the critical point.  I spent an inordinate amount of time at this bwlch as it took seven attempts before the Trimble complied with my wishes and reached its 0.1m accuracy level before data should be logged.  At one point I removed its battery and then re-booted it.  Why this happened I do not know, but wonder if five months inactivity had made it sluggish, a little like its owner, perhaps.

During the first bwlch survey I decided to take at least one more data set on the valley to valley traverse, and during this second survey I decided a third was needed.  This would give a good spread of results and show the lay of land over a 20 metre or so distance.

Gathering data at the bwlch of Allt y Moch

A greened track led up from the bwlch toward the summit, it was so good to be in such a place, it wasn’t dramatic, but it was a hill and I’d missed their openness over the last four months during the enforced and necessary lock down.

Once at the summit I proceeded to take four further data sets, three from near to where the 421m spot height appears on the Ordnance Survey 1:25,000 Explorer map and one from where the summit ridge continues north-westward.  During each data set I stood below the Trimble and looked out to the west across miles of cultivated, forested and in patches wild land toward the higher hills of the Aran and Berwyn.

Gathering data at the summit of Allt y Moch

Packing the Trimble away I retraced my route back to the connecting bwlch and headed down beside a fence line which took me to within a few metres of where I’d parked my car.  Allt y Moch would be a fine addition to the Y Pedwarau, we’ll just have to wait for the data to be processed until its status is hopefully confirmed.


Survey Result:


Allt y Moch
  
Summit Height:  419.7m (converted to OSGM15)

Summit Grid Reference:  SO 02202 84938

Bwlch Height:  389.6m (converted to OSGM15, from subsequent Trimble GeoXH 6000 survey)

Bwlch Grid Reference:  SO 02366 84827 (from subsequent Trimble GeoXH 6000 survey)


Dominance:  7.17%