Mapping Mountains – Significant Height Revisions – 200m Twmpau

 

Moel y Crio (SJ 199 696) 

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 a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips with assistance from Mark Trengove.

 

Moel y Crio (SJ 199 696)

The criteria for the list that this height revision 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 Moel y Crio, and it is adjoined to the Moel y Gamelin group of hills, which are situated in the north-eastern part of North Wales (Region A, Sub-Region A2), and it is positioned encircled by minor roads with the B5123 road farther to its east, and has the town of Yr Wyddgrug (Mold) towards the south-east.

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 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-evaluated and it was listed with an estimated c 14m of drop, based on the 292m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map at SJ 200 695 and an estimated c 278m bwlch height, based on interpolation of 5m contouring between 275m – 280m that appear on the Ordnance Survey 1:25,000 Explorer map.

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

However, it was not until the Trimble GeoXH 6000 survey that the details for this hill could be accurately re-assessed.  The summit height produced by this survey is 297.5m and is positioned at SJ 19988 69614, and this 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 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 Moel y Crio

Therefore, the new listed summit height of this hill is 297.5m and this was derived from a Trimble GeoXH 6000 survey, this is 5.5m higher than the previously listed summit height of 292m, which was based on the spot height that appears on the Ordnance Survey 1:25,000 Explorer map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Moel y Gamelin 

Name:  Moel y Crio 

OS 1:50,000 map:  116

Summit Height (New Height):  297.5m (converted to OSGM15) 

Summit Grid Reference:  SJ 19988 69614 

Bwlch Height:  276.8m (converted to OSGM15) 

Bwlch Grid Reference:  SJ 20406 69385 

Drop:  20.7m

 

Myrddyn Phillips (September 2022)