In order to allow fish to pass a 2.5-m-high weir, a ramp fishway made of non-concrete blocks was built on the River Borgne in Sion, Switzerland, in spring 2018.

Its geometrical design, which is particularly complex for a structure of this type, incorporates a central sinusoidal channel to concentrate the flow at low water levels. In order to ensure the required level of accuracy, the blocks were positioned using a grid of 3D points loaded into a motorised theodolite.