Mapping Mountains – Significant Height Revisions – 600m Twmpau and The Welsh Highlands - Uchafion Cymru

Cnicht (SH 645 466)

There has been a Significant Height Revision to a hill that is listed in the 600m Twmpau and the The Welsh Highlands – Uchafion Cymru, 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.

Cnicht (SH 645 466)

The criteria for the two listings that this significant height revision applies to are:

600m Twmpau – Welsh hills at or above 600m and below 700m in height that have 30m minimum drop, with an accompanying sub category entitled the 600m Sub-Twmpau consisting of all Welsh hills at or above 600m and below 700m in height that have 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

The 600m Twmpau by Myrddyn Phillips

The Welsh Highlands – Uchafion Cymru – This is the revised draft title for the Welsh 500m P15s list that takes in all hills in Wales at or above 500m in height with 15m minimum drop.  Accompanying the main list are three sub lists, these are; 500m Sub-Uchaf, 490m Sub-Uchaf and the Double Sub category.  The list is co-authored by Myrddyn Phillips and Aled Williams with the Introduction to the list published on Mapping Mountains in November 2015 and an update relating to the list appearing on Mapping Mountains on the 19^th June 2019.

The Welsh Highlands - Uchafion Cymru by Myrddyn Phillipa and Aled Williams

The name the hill is listed by is Cnicht, and it is adjoined to the Moelwyn Mawr group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A4085 road to its south-west, the A498 road to its north-west and the A470 road to its east, and has the small community of Croesor towards the south-west and the town of Blaenau Ffestiniog towards the east.

Prior to the Trimble GeoXH 6000 survey this hill was listed with an estimated c 106m of drop, based on the 689m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map, and an estimated c 583m bwlch height, based on interpolation of 10m contouring between 580m - 590m.

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

The summit height produced by the Trimble GeoXH 6000 survey is 690.7m, this is not a substantial height revision when compared to some revised heights, but it does come 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, Harvey or other interactive 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 with the data produced by the Trimble or by LIDAR analysis.

The Trimble GeoXH 6000 gathering data at the summit of Cnicht

Therefore, the new listed summit height of this hill is 690.7m and this was derived from a Trimble GeoXH 6000 survey.  This is 1.7m higher than its previously listed summit height of 689m which appears as a spot height on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.  However, this new height is in accordance with the 5m contouring on OS Maps. 

 

Extract from the OS Maps website

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Moelwyn Mawr

Name:  Cnicht

OS 1:50,000 map:  115

Summit Height (New height):  690.7m (converted to OSGM15)

Summit Grid Reference:  SH 64545 46613 

 

Bwlch Height:  585.7m (converted to OSGM15)

Bwlch Grid Reference:  SH 65589 47707

Drop:  105.0m

Myrddyn Phillips and Aled Williams (July 2019)