Technical Zone

What’s the problem?

Engineering and mapping projects generally use a two-dimensional horizontal coordinate system, usually with height as a separate system. For small projects, this could be a simple site grid, defined by a set of surveyed control points. A grid like this has no scale factor distortion, and so the relationship between plans and the ground is

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The SnakeGrid solution

SnakeGrid provides a single continuous near-zero distortion grid coordinate system for projects such as railways or pipelines that extend for hundreds of kilometres. Along the whole length of the route, we aim to keep scale factor distortion less than 20 parts per million, no matter how the height changes, and this will hold for several

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Practical use

A typical survey project associated with a road, railway or pipeline will usually establish a control framework with GNSS. This will give coordinates in a system such as WGS84, ETRS89, ITRF, or similar. Running these coordinates through a convertor such as SnakeGrid PointWise will put them into the required SnakeGrid system. Or this could be

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A note on datums

The SnakeGrid coordinates (E/N) inherit the datum of the geographic coordinates from which they are derived. Since these geographic coordinates are ultimately derived from GNSS surveys, the GRS80 ellipsoidal parameters are assumed. In practice, this means that SnakeGrid can be used with any modern datum that is related to WGS84 or ITRF. In Europe this will probably

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Merged grids

Quite often, a major rail route will also have smaller branches associated with it. Where these are within a few kilometres of the main route, it is usually possible to keep them on the same grid. However, there will be other situations in which one major route branches off from another, and goes in a

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Version history

SnakeGrid was originally known as RailGrid. When the name was changed (to reflect common usage since it was based on the Snake Projection, and applies to more uses than rail) the version sequencing was maintained. Consequently the versions are:   RailGrid v1 Internal prototype, not formally released. RailGrid v2 First application, only applicable to the

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