GSB file does not show up in library

[hhj308685]

I want to create a custom project-specific CRS (in Snakegrid, HS2TN15_NTv2). To accomplish this I have a GSB file that I would like to place in the right location in the Autocad Civil 3D folder structure.

My approach was the following:

1. paste the GSB file in the following folder under this path: 
   C:\ProgramData\Autodesk\Geospatial Coordinate Systems 14.08
   The first obstacle was that there are four different folders where only the number 14.0x changes. Which one should I choose? 
   
   I assume that the right one is the 14.08 one since Civil 3D is the last program that I installed on my machine.
   Then inside the 14.08 folder, I created a sub-folder that I called 'Snakegrid'. In the 'Snakegrid' sub-folder I pasted the GSB file that I also called 'Snakegrid'.
2. In the command line in Autocad Civil 3D I used the command 'MapCSlibrary'.
   
3. There I searched for the 'Snakegrid' GSB file, but nothing showed up.
   

Am I doing everything right so far in the process? And did I place the GSB file in the right location?

Thank you so much in advance for your help!

Caroline

[Pointdump]

Hi Caroline,
I think:
14.00 = 2014
14.04 = 2018
14.08 = 2022

"Then inside the 14.08 folder, I created a sub-folder that I called 'Snakegrid'. In the 'Snakegrid' sub-folder I pasted the GSB file that I also called 'Snakegrid'."
So far so good, but you're not there yet.

A GSB file basically says, if you're in this square, shift X this much and Y this much. A GSB is denser(smaller squares) in populated areas for greater accuracy.
The big question is, shifting what to what? A GSB file handles Geodetic Transformations between Datums, like between NAD83 and CSRS, Canada's version of NAD83.
So find out more about what Datum you're transforming.
Dave

[hhj308685]

Thank you for your comment Dave!

The conversion should be from OSGB1936 to Snakegrid. The issue is that the GSB file does not even show up when I look for it in the library inside AutoCAD. So I also can't set the CRS that it should convert the file from.

[Pointdump]

Caroline,
You need to create both a custom Coordinate System and a custom Geodetic Transformation. The custom Coordinate System is necessary because you'll be using a different Datum. Can you post the GSB and maybe a drawing in SnakeGrid Coords? Forum will accept pretty much anything if you Zip things together.
Dave

[Pointdump]

Caroline,
Further reading >>>Here<<<.
Dave