It is built one to two metres above the ground.
Using the information it would be possible to work out your position on Earth to within 500 metres.
It was moved to the spring and cut to 2,200 metres in 1909.
It was cut to 1,600 metres and moved to early July in 2005.
The main mass must have been moving at close to a metre a second.
These may be up to 30 metres (100 feet) above the ground.
There it can be found from near sea level up to 2300 metres.
The race's distance was changed to 2,150 metres in 1946.
Her personal best had been improved to 1.85 metres in May.
It was cut from 2,200 to 1,800 metres in 1985.