Benchmarks, red kites and ranging rods
1st February 2023
Yesterday, 31st January 2023, the Appraising Landscapes class undertook some basic surveying practice on the front lawn of FCH campus. On our way there we spotted two interesting phenomena: one possibly disappearing from, the other becoming more common in the British landscape.
Ordnance Survey Bench marks (BMs) are survey marks made by the OS to record height above Ordnance Datum (fixed as mean sea level at Newlyn in Cornwall). Most commonly, the BMs are found on buildings or other semi-permanent features. Although the main network is no longer being updated, the record is still in existence and the markers will remain until they are eventually destroyed by redevelopment or erosion. There are two visible bench marks carved into buildings on the FCH campus, one on the north side of the Bodley Building (see photo). The height of the horizontal mark is 57.1409m above OD.
Above the quadrangle we were amazed to observe a red kite (Milvus milvus) wheeling around in the clear blue sky. The reintroduction of these large birds of prey has been a conservation success story. The species was lost from the landscape many years ago, then a few pairs were initially reintroduced (early 1990s) into the Chilterns and mid Wales to breed. This they have done so well that they are a common sight in those areas and indeed are extending their range, now obviously to Cheltenham. Is this a sign of urban rewilding?
The main aim of the surveying class was to undertake a simple “line and level” survey. This involved measuring and ‘fixing’ a number of features (trees, lampposts, kerb edges) as offsets to the base lines, then deriving their relative heights using levels. While most site surveys needed for professional jobs would be commissioned externally, it is useful for intending landscape architects to understand the principles of planimetric and level survey, partly because small garden-scale surveys needn’t be outsourced and also, perhaps more importantly, spending some time walking around the site appreciating the undulations “through the soles of your feet” is the best way to reinforce the micro-relief of the place in a designer’s mind.
Bob Moore 1.2.23