Geographic coordinate system missing


I'm currently working in a big railway project that uses a bespoke GCS.

I was following a forum post that explaining how to create a transformation. In the process the seed file "UserOverrideGeodeticTransformSeed.asc" needed to be altered.

The heading of the file contain the following text:

"# In case of absolute necessity it is possible to override the list or
# order of the grid shift files for a specific datum transformation.
# This should only be done if no other solution is available.
# Bentley Systems would be glad to introduce new files directly
# referenced by the built-in system dictionary as part of a refresh to
# its software. Contact Bentley system through the normal support channel."

As you can imagine this new GCS is a big headache with all the legacy data.

Is there anyone in the position to help?

Thank you in advance for your time.



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  • You'll want to know what coordinate system the legacy data is in. Often this will be the current state plane or similar.

    This a typical scenario of a site in the states, your needs may be different:

    Make a backup copy. Open the file, attach the correct system. Microstation will ask if the existing elements need re-drawn, this can be tricky, often MS thinks the old data is international feet and wants to convert to US survey feet. So say no. You should now have a georeferenced file with the elements in the correct position. Since you say it's a large site, you can do a confidence check with GIS data or even a good georeferenced aerial.

    A similar technique can be used by referencing the legacy data.

    Connect r17 self-employed-Unpaid Beta tester for Bentley

  • This a typical scenario of a site in the states, your needs may be different

    The OP could be a little clearer on the details of his GCS and the legacy data.  From the available evidence, I believe that he is working on the HS2 project in the UK.  If I've guessed correctly, then the overall GCS is the UK national grid, but he may be using a set of localised high-resolution grids provided by SnakeGrid.  He'll be working in metric units.

    Regards, Jon Summers
    LA Solutions

  • Thank you both for your quick reply.


    Jon summarized pretty well.


    I’m using MicroStation Connect Update 6 – V10.06.00.38.

    The project is HS2 and is using a provided bespoke GCS. The legacy data it’s on the national system OSGB36 (with a mix of two revisions 2002 and 2015 – you can find a well summarized article here).


    We are using a 3rd party software to do the conversion for us outside MicroStation, which is not ideal and not as neat as the Bentley in-built conversion. We also lose the ability to use google Maps/Earth in-built tool that adds a lot of value.


    It’s important for us to have the “conversion trick” well sorted, besides being able to use existing data, we will deliver the as-builts in both systems (OSGB36 and SnakeGrid). Also MicroStation is widely used in the rail sector here in the UK, and would give the conversion power to any user, not to a specific team in a specific project – if this makes any sense.


    Ideally we would be able to flip between any OSGB 02 / OSGB 15 / SnakeGrid (HS2P40+1) systems in MicroStation Connect.


  • Ideally we would be able to flip between any OSGB 02 / OSGB 15 / SnakeGrid (HS2P40+1) systems

    The solution would be for SnakeGrid to generate a MicroStation GCS specification for each local grid.  They already have SnakeGrid Transformer, an Add-In for MicroStation. Could that be extended to offer that facility?

    I notice that SnakeGrid Transformer is developed for SnakeGrid by UK company dhp11.

    Regards, Jon Summers
    LA Solutions

  • We are aware of the dhp11 SnakeGrid transformer The project opted to use FME


    None of this solutions work seamlessly. There is a few pros and cons on each software, some will break(drop) all elements or not process .pod files… and so on.


    Both solutions have a patchy feeling, none is quite there, hence my quest for a better integrated solution. Besides we already use a software with the capabilities. For all sort of reasons if we have to buy another software, in the end of the day we are not being very efficient.