Snake Projection
The Snake Projection is a coordinate system which projects geographical coordinates onto an Easting/Northing grid [1]. 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[2]). 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 20km of the centre line[3]. The principle advantage of the projection is that, for the corridor defining the design space, distances measured on the ground have a 1:1 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[4]). 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[5], including that of the HS2 London to Birmingham line[6]. For the London to Glasgow West Coast Main Line the distortion in the Snake Projection used is no greater than 20ppm within 5km of either side of the track[7].
References
- ↑ Iliffe, J.C.; Arthur, J.V.; Preston, C. (2007). "The Snake Projection: A Customised Grid for Rail Projects". Survey Review. 39 (304): 90-99. doi:10.1179/003962607X165041. Retrieved 5 February 2018.
- ↑ Reynolds, John (2011). An Introduction to Applied and Environmental Geophysics (2 ed.). John Wiley & Sons. ISBN 978-0-471-48535-3. Search this book on
- ↑ Iliffe, J.C. (2017). "The development and analysis of quasi-linear map projections". Cartography and Geographic Information Science. doi:10.1080/15230406.2017.1325332. Retrieved 5 February 2018.
- ↑ SCSI. "Map Projections and Scale Factor". SCSI. Society of Chartered Surveyors Ireland.
- ↑ XYHT. "Corridor Projections Solved". XYHT. Flatdog Media. Retrieved 5 February 2018.
- ↑ UCL. "HS2 becomes fifth project this year to adopt SnakeGrid system". CEGE. UCL. Retrieved 5 February 2018.[permanent dead link]
- ↑ Uren, John; Price, Bill (2010). Surveying for Engineers (5 ed.). Basingstoke: Palgrave Macmillan. Search this book on
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