Add string writer for OGC WKT-CRS version 2

[juliohm]

Issue

The OGC WKT-CRS 2 standard defines a textual representation of coordinate reference systems that is widely adopted in industry. This textual representation is mostly used in file formats as metadata.

We need to implement a new CoordRefSystems.wkt(crs::CRS)::AbstractString utility function to convert CRS objects into strings. The implementation should adhere to the standard (no GDAL/PROJ extensions), and be tested against mature implementations (e.g. GDAL) in our test suite.

Bounty

If you enjoy working with specifications, consider helping with this task. I am reserving a /bounty $250 for it. The implementation should fit nicely to the current code base in terms of software engineering best practices and code style.

Tips

• The function CoordRefSystems.string2code in this repository does the opposite operation. It takes a WKT string (or other standards) and returns the integer code of the CRS.
• The https://epsg.io website provides this feature. If you search for a given CRS code or name like "Mercator" you will see the different strings at the bottom of the page, including OGC WKT 2: https://epsg.io/53004

You can even access the string directly with a HTTP request by pressing the button "Open" in the screenshot. It will direct you to https://epsg.io/53004.wkt2 This is not a valid solution as it requires internet connection during the function call.

• If the EPSG database can be downloaded during the installation of the package with DataDeps.jl, we could explore the feasibility of storing the database locally on the host machine, and querying it with the given EPSG integer code. We would also need to make sure we are not infringing licensing terms by doing that. I doubt it, but worth checking.

[algora-pbc]

💎 $250 bounty • JuliaEarth

Steps to solve:

1. Start working: Comment /attempt #245 with your implementation plan
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Attempt	Started (GMT+0)	Solution
🟢 @asr2003	Feb 13, 2025, 1:09:23 PM	WIP

[asr2003]

/attempt #245

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[asr2003]

@juliohm I have just started understanding the OGC WKT-CRS 2 specification and will complete this at this weekend as i will not available with my desktop until tomorrow though