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.
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.
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 our 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 the 2,000ft mountains.
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!