Craig Dolfudr – North
Top (SH 822 317)
There has been a Significant Height Revision to a
hill that is listed in the The 500-Metre
Tops of England and Wales, with the summit height, bwlch height and their
locations, the drop and status of the hill derived from LIDAR analysis
conducted by Aled Williams.
%20-%20LIDAR%20hill%202.jpg) |
| LIDAR image of Craig Dolfudr - North Top (SH 822 317) |
The criteria for the list that this height
revision applies to are:
The
500-Metre Tops of England and Wales
are affectionately known after their hill list compiler; Michael Dewey. This list mixes metric and imperial height in
its criteria to bookend up to the 2000ft height band and takes in all hills in
England, Isle of Man and Wales that are 500m and above and below 2000ft
(609.6m) in height that have 30m minimum drop.
 |
| Mountain tables by Michael Dewey |
Michael Dewey died on the 5th November
2022. His wife; Gillian wished for this
list to be carried on and made provision for it to be co-authored by Myrddyn
Phillips. Michael will always be the
compiler and originator, it’s just that he’s now got a co-author to safeguard
and carry this list on.
The name given the hill by Michael Dewey is Craig Dolfudr –
North Top and it is adjoined
to the Arenig Fawr group of hills, which are situated in the central part of North Wales, and it is
positioned with a minor road to its north and the A494 road to its south-east,
and has the small community of Llanuwchllyn towards the east south-east.
 |
| Extract from the Ordnance Survey 1:50,000 Landranger map |
When the original list of Deweys appeared in the Mountain tables book published by Constable in 1995, this hill was listed with a 519m summit height, based on the spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.
%20-%201%2025000.jpg) |
| Extract from the Ordnance Survey 1:25,000 Explorer map |
Since the original publication of this list there have been a number of maps made available online. Some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website. Whilst others were digitally updated such as the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map, whilst others are current and digitally updated such as the interactive mapping on the Magic Maps and WalkLakes websites, and it is the Ordnance Survey series of Six-Inch maps that formed the basis in the change of the listed height of this hill.
The Ordnance Survey series of Six-Inch maps formed the base map Ordnance Survey used for many decades leading to the production of the 1:10,000 Series of maps, both have now been superseded by the digitised Master Map, and it is this series of maps that give a 1709.9ft (521.18m) Bench Mark on the summit of this hill.
%20-%20Six-Inch.jpg) |
| Extract from the Ordnance Survey series of Six-Inch maps |
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.
%20-%20LIDAR%20summit%202.jpg) |
| LIDAR summit image of Craig Dolfudr - North Top (SH 822 317) |
LIDAR analysis gives the summit of this hill as 521.4m positioned at SH 82250 31702, 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, 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 other GNSS equipment 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.
Therefore, the new listed summit height of this hill is 521.4m and this was derived from LIDAR analysis, this is 2.4m higher than the originally listed summit height of 519m, which was based on the spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.
The full details for the hill are:
Group: Arenig Fawr
Name: Craig Dolfudr – North Top
OS 1:50,000 map: 124, 125
Summit Height (New Height): 521.4m (LIDAR)
Summit Grid Reference: SH 82250 31702 (LIDAR)
Bwlch Height: 444.8m (LIDAR)
Bwlch Grid Reference: SH 81324 31319 (LIDAR)
Drop: 76.6m (LIDAR)
Myrddyn Phillips (November 2026)