Examples

SnakeGrid was initially developed to be used on the west coast main line from London to Glasgow. In this first application, a grid was developed such that the deviation from unity of the scale factor on the 645 km track was within 11 parts per million at all points – even though the height of this route ranged from 0 m to 300 m above sea level.

Following the success of this project, the software was adapted to be used anywhere. As can be seen in the map on the left, it has now been used to derive true scale grids for all of Network Rail’s primary routes, as well as several others in Great Britain and elsewhere. Some of these are stand-alone independent grids – such as that developed for the Crossrail project, or for the work on the re-opening of the route from Edinburgh to the Borders. Others are part of interlocking systems – for example the grid developed for the London Paddington to Swansea route accommodates the direct route and the branch via Bath, and joins seamlessly at Reading to the grid developed for the route to Plymouth.

SnakeGrid is ideally suited to projects that cross international boundaries, such as long distance pipelines or major rail routes. A single seamless grid can be developed for the project, and then additional software supplied that transforms as necessary to and from each national coordinate reference system. So for example, engineers can develop route alignments in the SnakeGrid coordinate system, secure in the knowledge that the scale factor distortion is minimal and that what they are designing can be realised in practice on the ground. To aid this, digital mapping data and orthophotography from each of the national jurisdictions that the route passes through can all be transformed into the SnakeGrid coordinate system as contextual information. If necessary, finished designs can be transformed into national coordinate reference systems for discussions with clients.

Further information on the use of SnakeGrid on railway routes in Great Britain, and the experiences of the engineers who have worked with it, can be found in the October 2008 edition of Aspects, the in-house magazine of Network Rail.