RE: SnakeGrid - How is OpenRail / ASD working with this?

Jim Turner — Fri, 17 May 2019 11:50:45 GMT

There is a recent development which will enable the HS2 SnakeGrid to be available within the standard GCS library. This will initially be rolled out to Microstation and from there to further products. This will reduce the need for data duplication and enable, for example, web map services (WMS) to be re-projected on-the-fly to HS2 SnakeGrid and GCS transforms to the SWA.

This will be applicable to HS2 phase 1+2a; the GCS uses an NTv2 transform + Transverse Mercator projection. It will be available in Microstation update 13 however will require manual installation of the transformation files. MS CE Update 14 will have the files distributed.

Two GCS will be available: HS2_Snake_2002 and HS2_Snake_2015. These are essentially the same GCS - the difference is the transformation used for conversions into other GCS:

Use HS2_Snake_2002(HS2TN02) when converting to/from OSTN02.BritishNatGrid
Use HS2_Snake_2015(HS2TN15) when converting to/from OSTN15.BritishNatGrid
Use HS2_Snake_2015(HS2TN15) when converting to/from ETRS89 OS Net v2009 latitude/longitude (current OS Active Network)

Note that the HS2TN02 transform is equivalent to using the HS2P1+14 SnakeGrid parameter file. If converting into lat/lon using HS2TN02/HS2P1+14 then these coordinates are only compatible for use with the legacy OS Active Network (OS Net v2001).