Ordnance Survey recently published an article on the survey
of Calf Top and its elevation in height to 2,000ft. The original article and a link to it on the OS
Blog appear below.
Calf Top – England’s last
mountain
Guest blog by Myrddyn Phillips, Hill Data
& Mountain Surveys
Calf Top (SD 664 856) is a
rather unassuming hill which is approximately 6km south of Sedbergh in the
Yorkshire Dales. It rises above the deep cleft of Barbondale to its east
and Dentdale to its north, and although not the highest hill in the area it is
quite prominent above its surroundings.
 |
| Calf Top |
However, it isn’t the hill’s prominence that is of interest, it
is its height, and being a mountain surveyor those hills that are given a 609m
spot height on Ordnance Survey maps are particularly interesting, as this
height equates to just under 2,000ft, with 609.6m the metric equivalent of this
all important imperial height. All important, as 2,000ft is generally regarded
as the benchmark height in England and in Wales for when a hill is promoted to
the dizzying ranks of a mountain.
Along with two colleagues,
Graham Jackson and John Barnard, we surveyed Calf Top using precision levelling
and GPS equipment in 2010. We were so enthusiastic to survey the hill
that we collected a two hour data set from its summit on our first visit and
then ever gluttons for punishment we re-visited the following month and
gathered a four hour data set from its high point.
 |
| The Leica 530 gathering data at the summit of Calf Top. (L-R) John Barnard and Graham Jackson |
These data were sent to
Mark Greaves at Ordnance Survey who processed them through Bernese software
with the resulting height of 609.58m, just a tantalizingly and ever so close
result to that all magical 609.6m, just 2cm short!
Our story now dashes
forward six years to the present day and the release of the new geoid model by
Ordnance Survey, this is named OSGM15. Mark evaluated the 2010 data against the
new model and the resulting analysis meant that England has a new mountain for
everyone to climb:
I can confirm that I computed
the slightly more accurate value for Calf Top at 609.606. This is based
on tweaking the 2010 survey results to take account of the update in OS Net
coordinates and then applying the new OSTN15/OSGM15 transformation. Mark Greaves [Read the blog on Monday when Mark tells us more about
OSTN15]
This new value has given mountain surveyors (me included) great satisfaction as although or hills are beautiful places, with an abundance of variety from the dramatic Highlands of Scotland to the wilds of mid Wales, there's now a rather eloquently shaped hill, that is quintessentially English that has been elevated to the ranks of 2,000ft mountains.
 |
| The Leica 530 gathering data at the summit of Calf Top |
There are very few
remaining hills in England whose map height sparks interest for those budding
independent surveyors to clamber up and wait patiently whilst the minimum of
two hours of data is gathered for Ordnance Survey verification, and because of
this, this rather special little hill is now so much larger in thought and
known height and it is elevated to mountain status. In all probability
Calf Top will be the last such hill to become a mountain in England.
Calf Top is a fine
mountain, one of those steep sided grass laden mountains that seem to epitomise
parts of England, and I suspect its popularity will now be elevated, the same
as its height!
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