Snake Projection  The Snake Projection is a coordinate system which projects geographical coordinates onto an easting and northing grid. The parameters defining the Snake Projection must be tailored for specific projects; the most typical use is with large-scale linear engineering projects such as rail infrastructure, however the projection is equally applicable to any application requiring a low distortion grid along a linear route (e.g. pipelines and roads). The name of the projection is derived from the sinuous nature of the projects it may be designed for. Typical map projection distance distortion characteristics of a Snake projection are minimal over the whole route within approximately 20 kilometres of the centre line. The principal advantage of the projection is that, for the corridor defining the design space, distances measured on the ground have a one to one relationship with distances in coordinate space (i.e. no scale factor need be applied to convert between distances in grid and distances on the ground). The main disadvantage is that away from the design corridor the distortion of the projection is not controlled. The Snake Projection is the engineering coordinate system used for a significant proportion of primary rail routes in the UK, including that of the HS2 London to Birmingham line. For the London to Glasgow West Coast Main Line the distortion in the Snake Projection used is no greater than 20 parts per million within 5 kilometres of either side of the track.