TP6986 - Windy Bank
|Grid reference :||SD 70487 31082|
|Flush Bracket Number :||S4703|
|Current use :||none|
|Historic use :||Secondary|
|Nearest town :||Rishton|
On the top of Windy Bank, over the new Inns, stands this lonely Trigpoint, open to the elements at a height of approximately 946 feet above sea level.
In the United Kingdom, trig points are typically concrete pillars, and were erected by the Ordnance Survey.
The process of placing trig points on top of prominent hills and mountains began in 1935 to assist in the accurate retriangulation of Great Britain. In low lying or flat areas some trig points may be only a few metres above sea-level. When all the trig points were in place, it was possible, in clear weather, to see at least two other trig points from any one trig point. Careful measurements of the angles between the lines-of-sight of the other trig points then allowed the construction of a system of triangles which could then be referenced back to a single baseline to construct a highly accurate measurement system that covered the entire country.
In most of the United Kingdom, trig points are truncated square concrete (occasionally stone) pyramids or obelisks tapering towards the top.
On the top a brass plate with three arms and a central depression is fixed. A benchmark is set on the side, marked with the letters "O S B M" (Ordnance Survey Bench Mark) and the reference number of the trig point.
Within the trig point, there are concealed mountings for a specialised theodolite, which was temporarily mounted on the trig point while measurements were taken.
Many of them are now disappearing from the countryside as their function has largely been superseded by aerial photography and digital mapping using lasers and GPS measurements.
Trigonometrical stations are grouped together to form a network of triangulation. Positions of all land boundaries, roads, railways, bridges and many other infrastructures can be accurately located by the network.
Trigonometrical stations are essential to the construction of modern infrastructure. Apart from the known stations set up by government, some temporary trigonometrical stations are set up near construction sites for monitoring the precision and progress of construction.
Some trigonometrical stations are equipped with Global Positioning Systems which greatly improve their accuracy.
Although many stations are no longer required for surveying purposes, they remain useful to hikers as navigational aids when hill-walking.
Once the bench mark is reached, several others can be seen on the surrounding hillsides, all used as explained above.