SnakeGrid

How is a SnakeGrid created?

In order to create a bespoke SnakeGrid  parameter file we require details of your surveying project.  This could be a verbal description, but ideally it would be accompanied by a simple map.

Include in this any particular requests that you have for the characteristics of the grid. For example, if you want it to match with an existing grid at any particular point (generally only one is possible) or if it has difference branches that you would like to include on one single grid.

We can normally accommodate branches a few kilometres apart on the same seamless coordinate system. However, where different branches diverge more substantially we can create a separate grid that is continuous at an indicated junction point. Within a few kilometres of this junction point the two grids will be identical to within a few millimetres, thus enabling continuous surveys across the join.

The next stage will be to send us a coordinate description of the route of the project. This is referred to as a set of “seed points” and simply means selected points along the route, spaced at about 1 – 2 kilometres, with three dimensional coordinates (latitude, longitude and height) in the WGS84 system or one of its equivalents (ITRF, ETRF89, NAD83, etc). These only need to be accurate to about 100 metres in plan and 10 – 20 metres in height. It is emphasised that the height needs to be above the WGS84 ellipsoid, and not above a local land levelling datum. Once we have this information we then create a SnakeGrid parameter file that defines the grid system to be used on your project.

Who else is using SnakeGrid?

The SnakeGrid software was originally commissioned from University College London by  Network Rail for use on the West Coast Main Line from London to Glasgow. It has  subsequently been used on many other rail routes in Great Britain and overseas, including  the East Coast Main Line from London to Edinburgh. Over the 630 km length of the  latter, for example, a grid was designed that gave scale factor and height distortion of less  than 11 parts per million (ppm) along the whole track. Within a few kilometers either side  the distortion is less than 20 ppm. See the section on Examples of SnakeGrid in use for  details of other projects.

How does Licensing work?

Licensing is managed by UCL Busines PLC. The usual arrangement is that you pay a one-off fee to have a grid designed for your project. After this  you have a permanent licence to use SnakeGrid on your project. However, we can offer alternatives such as  annual licensing arrangements if these are more suitable to your needs.

Earlier versions of the software

The current version of SnakeGrid is version 4, and is in fact a completely new and re-designed  version of the software. This has enabled us to make some radical improvements to the way it  works, including:

  * Greatly increased speed – on a typical desktop PC it can handle around a million  coordinate conversions per minute.

  * A greater variety of input/output formats supported.

  * A better interface, with more information supplied to the user.

  * Greater flexibility in the way that grids are designed – we can rectify grids to give zero  convergence at specified locations, for example, or accommodate diverging branches with  seamless coordinates at the junction point.

  * Easier to manage parameter files for different projects.