Setting Up in the Real World - SnakeGrid

What is SnakeGrid?

SnakeGrid takes a linear alignment and lays it out on a flat plane maintaining low distortion along a strip 1 mile wide each side of the alignment. This allows accurate measurements of distance and angle within this strip.

This is not a Geographic Coordinate System (GCS) that relates to established geoids that could be added to MicroStation's GCS library, but a self-contained coordinate system unique to each individual alignment. If, for example, two SnakeGrids cross at a common real world location, the SnakeGrid coordinates will be totally different for each alignment.

It is possible to use dhp11's SnakeGrid Transformer to transform some MicroStation elements between SnakeGrids, and conventional GCSs such as OSGB or project specific grids such as the London Survey Grid and (for example) the Reading project grid. This involves creating transformed copies of the selected elements (which can only be from a subset of MicroStation elements, those that are/can be defined by vertices) so is suitable only for simpler 2D geometry and 3D triangulated surfaces. These elements, including the alignments, are exploded to their most basic geometric parts, their vertices are then transformed to the target GCS.

Complex 3D geometry would also need to be exploded to give access to the vertices, reducing the result to a useless mass of lines; so there is no point attempting to transform such complex elements.

Simpler elements, such as track alignments, can be transformed and would also be exploded to constituent elements, but being simpler would still be useable.

Once transformed to a known GCS, geometry can be referenced using conventional MicroStation geo-referencing techniques for work with facilities/buildings that relate to the alignment.

Maintaining duplicate copies of data is inevitable using this workflow. The SnakeGrid version will generally be the master, the transformed copy a child read-only version. Version management is crucial to the success of this workflow, possibly enforced by a ProjectWise workflow that requires the child to be updated before changes to the master can be committed.

Facility/Building Design Workflow:

To work with AECOsim Building Designer we need to model within the Solids Working Area. The recommended workflow is to model individual buildings/facilities near to the Design File Centre unrotated then use geo-referencing to reference the real-world context to the AECOsim Building Designer models. Geo-referencing can also be used to relate individual buildings/facilities to each other as well as the context, as shown in this illustration:

Drawings and visualizations that include the site context can be created from these geo-referenced composites.

The individual buildings/facilities along with their footprints and/or setting out/location points can be referenced into the transformed site model from where the footprints and/or setting out/location points could be transformed back to SnakeGrid for coordination purposes. (Potentially the edges of simplified building/facility envelope volumes could also be transformed back to SnakeGrid for volumetric coordination, the volumes would need to be rebuilt from the edges after the transform.)


For more information on Geo-referencing with MicroStation, AECOsim Building Designer and other related applications please refer to product help and the articles in this blog series: Series Index - Setting Up in the Real World