Showing posts with label Pt. 170.7m (SJ 193 018). Show all posts
Showing posts with label Pt. 170.7m (SJ 193 018). Show all posts

Tuesday, 29 June 2021

Mapping Mountains – Significant Name Changes – 100m Twmpau

 

Pt. 170.7m (SJ 193 018) 

There has been a Significant Name Change to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips. 

Pt. 170.7m (SJ 193 018)

The criteria for the list that this name change applies to are:

100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m 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 100m Twmpau by Myrddyn Phillips

The hill is adjoined to the Carnedd Wen group of hills which are situated in the south-eastern part of North Wales (Region A, Sub-Region A4), and it is positioned with a minor road to its north, the B4385 road to its west, the B4390 road to its south and the A483 road to its east, and has the village of Aberriw (Berriew) towards the south-west. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was listed under the transposed name of Allt Upper, which is a prominent name that appears near the summit of this hill on the contemporary Ordnance Survey 1:25,000 Explorer map.


Allt Upper169mSJ193018136216Included by contour configuration

 

During my early hill listing I paid little regard to name placement on the map, or the meaning of names and to what feature the name was appropriately applied to.  Therefore, I prioritised names for listing purposes that I now understand are either inappropriate or where another name is viewed as being more appropriate, with the previously listed name of Allt Upper applying to a district and not necessarily to the hill itself. 

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

This is not a practice that I now advocate as with time and inclination place-name data can be improved either by asking local people or by examining historic documents, through this form of research an appropriate name for the hill can usually be found.  However, occasionally even when research is conducted an appropriate name for the hill may not be found, and on such occasions the listing protocol is to use the point (Pt. 170.7m) notation, and for this hill, this is such an example. 

Therefore, the name this hill is now listed by in the 100m Twmpau is Pt. 170.7m, and this is being used as the author has not found an appropriate name for it either through historic research and / or local enquiry. 

 

The full details for the hill are: 

Group:  Carnedd Wen 

Name:  Pt. 170.7m

Previously Listed Name:  Allt Upper 

OS 1:50,000 map:  136

Summit Height:  170.7m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SJ 19323 01898 (Trimble GeoXH 6000)

Bwlch Height:  132.5m (LIDAR)

Bwlch Grid Reference:  SJ 18115 01656 (LIDAR)

Drop:  38.2m (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

Myrddyn Phillips (June 2021)

 

 

 

 

 

 

 

 

Sunday, 27 June 2021

Mapping Mountains – Significant Height Revisions – 100m Twmpau


Pt. 170.7m (SJ 193 018) 

There has been a Significant Height Revision to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis and a subsequent Trimble GeoXH 6000 survey conducted by Myrddyn Phillips. 

Pt. 170.7m (SJ 193 018)

The criteria for the list that this height revision applies to are:

100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m 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 100m Twmpau by Myrddyn Phillips

The hill is being listed by the point (Pt. 170.7m) notation as an appropriate name for it either through local enquiry and / or historic research has not been found by the author, and it is adjoined to the Carnedd Wen group of hills which are situated in the south-eastern part of North Wales (Region A, Sub-Region A4), and it is positioned with a minor road to its north, the B4385 road to its west, the B4390 road to its south and the A483 road to its east, and has the village of Aberriw (Berriew) towards the south-west. 

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was included in the main P30 list, with a 169m summit height based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map. 

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

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. 

LIDAR image of Pt. 170.7m (SJ 193 018)

The summit height produced by LIDAR analysis is 170.6m, but as the summit of this hill has now been surveyed with the Trimble GeoXH 6000, resulting in 170.7m at SJ 19323 01898, it is this result that is being prioritised for listing purposes 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 Pt. 170.7m (SJ 193 018)

Therefore, this hill’s new listed summit height is 170.7m and this was derived from a Trimble GeoXH 6000 survey, this is positioned at SJ 19323 01898 and is 1.7m higher than the previously listed summit height of 169m which was based on the spot height that appears on the contemporary Ordnance Survey 1:25,000 Explorer map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Carnedd Wen

Name:  Pt. 170.7m

OS 1:50,000 map:  136

Summit Height (New Height):  170.7m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SJ 19323 01898 (Trimble GeoXH 6000)

Bwlch Height:  132.5m (LIDAR)

Bwlch Grid Reference:  SJ 18115 01656 (LIDAR)

Drop:  38.2m (Trimble GeoXH 6000 summit and LIDAR bwlch)

 

Myrddyn Phillips (June 2021)

 

 

 

 

  

Tuesday, 11 May 2021

Mapping Mountains – Trimble Surveys – Carnedd Wen

 

08.03.21  Pt. 170.7m (SJ 193 018) and Lower Cil (SJ 185 016)

Pt. 170.7m (SJ 193 018)

Two weeks ago Linda, Nic and I walked on the canal towpath and visited a hill positioned above Berriew which is known locally as Llwynderw Hill.  This gave a good circular walk using the Red Lane as our way back toward our inward route on the towpath.  Today I was out with Linda and had suggested walking beyond where we had previously left the towpath, visiting two relatively small heighted hills before using the lanes and public footpaths close to the summit of Llwynderw Hill as our descent route. 

With strong winds and rain forecast mid-week the continued settled conditions were not to be missed and therefore I met Linda at 11.00am to saunter on the canal towpath, chatting away about all manner of things past the Belan Lock and onward.  The hum of traffic on the Welshpool to Newtown road slowly ebbed in to the distance with silence taking over the land.  This was only broken by our conversation and the ever present background of birdsong.  This is an accompaniment to spring’s arrival when renewed warmth filters down through the chilled months of winter.  Today the conditions were blissful, not in a dramatic sense but in one where contentedness was easily found. 

The canal towpath leading toward our first hill of the day

We stopped for lunch at a picnic table close to where we would leave the canal tow path for a narrow country lane, and once sandwiches, boiled eggs and chocolate bars had been devoured we set off up the lane toward Lower Brithdir, where a public footpath guided us over a stream beside fields full of newly born lambs suckling their mothers as their thin tails wagged this way and that. 

LIDAR image of Pt. 170.7m (SJ 193 018)

Beyond the stream we followed a rising field toward the summit of our first of two hills of the day.  Both had been LIDARed prior to our visit and although it would have been easy to determine the high point of this first hill, I nevertheless used the ten figure grid reference produced by LIDAR to zero in on its summit.  Once found I placed the Trimble on top of my rucksack, measured the offset between its internal antenna and the ground at its base and stood back as six minutes of data were collected. 

Gathering data at the summit of Pt. 170.7m (SJ 193 018)

Once the Trimble was packed away we made our way across the field and called at Cefn-yr-allt, which I hoped was a farm, it wasn’t, so any thought of finding an appropriate name for either the hill or the upper field that had just been Trimbled would have to wait for another day as the person who answered the door could not help with my enquiry. 

LIDAR image of Lower Cil (SJ 185 016)

Our second hill was relatively near and once we were walking down the access track leading to Cefn-yr-allt we looked out for the most convenient way in to the field that rose toward the top of the hill.  Our way up was via a fence beside a particularly boggy area, disturbing two ducks as we did so.  We were soon on top, with the summit crowned by a small brick enclosed water reservoir.  Once I’d chosen the spot for Trimble placement I joined Linda sitting beside the small brick wall below the Trimble and waited for the allotted data to be gathered and stored. 

Gathering data at the summit of Lower Cil

Our onward route took us down to Lower Cil Farm where we met George Pritchard.  We chatted for a number of minutes and he explained that he was the tenant having been here for 34 years, moving from the Oswestry area to farm this land.  He said that the land taking in the summit of this hill is known by the farm name; Lower Cil, a practice that is not uncommon.  George directed us through his farm yard toward the gate which led down to a stream; warning us that getting over the stream may be problematic. 

Across the fields toward the stream 

We sauntered across fields down to the stream, thankfully it proved relatively easy to cross, but the last few days had been dry, following a downpour it would no doubt be a tricky place to get over, and our onward route necessitated us being on its opposing bank. 

A chicken caravan!

Late afternoon with the Breiddin as backdrop

Rising fields soon took us to a track and then lane which brought us to Cefn-hilin; a farm we called at a couple of weeks ago after visiting the summit of Llwynderw Hill.  We now had options for our descent route; all would in time either lead us on to the Red Lane and / or back to the canal tow path.  We opted for a route taking in new ground following a descending lane through Belan and then across fields above the canal with Welshpool spread out before us with the rising Breiddin as backdrop. 

A gentle land

Dusk approaching

It proved a lovely route down, stopping and looking back as the sun sank forever lower leaving a silvered sheen in the sky as dappled clouds were highlighted pink.  I left Linda in town and slowly walked back home happy and content with the day’s outing. 

 

Survey Result: 

 

Pt. 170.7m (significant name changes)

Summit Height:  170.7m (converted to OSGM15, Trimble GeoXH 6000) (significant height revision) 

Summit Grid Reference:  SJ 19323 01898 (Trimble GeoXH 6000) 

Bwlch Height:  132.5m (LIDAR)

Bwlch Grid Reference:  SJ 18115 01656 (LIDAR)

Drop:  38.2m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  22.40% (Trimble GeoXH 6000 summit and LIDAR bwlch)


 

 

Lower Cil (significant name change)

Summit Height:  159.3m (converted to OSGM15, Trimble GeoXH 6000) 

Summit Grid Reference:  SJ 18556 01630 (Trimble GeoXH 6000) 

Bwlch Height:  137.8m (LIDAR)

Bwlch Grid Reference:  SJ 18939 01777 (LIDAR)

Drop:  21.5m (Trimble GeoXH 6000 summit and LIDAR bwlch) (100m Sub-Twmapu addition)

Dominance:  13.49% (Trimble GeoXH 6000 summit and LIDAR bwlch)


 

 

For further details please consult the Trimble Survey Spreadsheet