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:
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
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
Dave Stoll
Las Vegas, Nevada
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.
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
Dave Stoll
Las Vegas, Nevada
Caroline,
Further reading >>>Here<<<.
Dave
Dave Stoll
Las Vegas, Nevada
Can't find what you're looking for? Ask the community or share your knowledge.