Remote datasets: Add "uncertainty" parameter to "load_earth_free_air_anomaly" to load the "free-air anomaly uncertainty" dataset

[yvonnefroehlich]

Description of proposed changes

Add the parameter uncertainty to the function load_earth_free_air_anomaly to load the dataset "IGPP Earth Free-Air Anomaly Uncertainty"

• Official documentation: https://www.generic-mapping-tools.org/remote-datasets/earth-faaerror.html
• Recipe: https://github.com/GenericMappingTools/gmtserver-admin/blob/master/recipes/earth_faaerror.recipe

Adresses #2431

Preview: https://pygmt-dev--3727.org.readthedocs.build/en/3727/api/generated/pygmt.datasets.load_earth_free_air_anomaly.html

Reminders

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst.
• Write detailed docstrings for all functions/methods.
• If wrapping a new module, open a 'Wrap new GMT module' issue and submit reasonably-sized PRs.
• If adding new functionality, add an example to docstrings or tutorials.

Slash Commands

You can write slash commands (/command) in the first line of a comment to perform
specific operations. Supported slash command is:

• /format: automatically format and lint the code

[seisman]

I don't like the parameter name data_source here, since these two datasets acutally comes from the same source.

Maybe uncertainty=True to use the faaerror data?

[seisman]

Looks good to me except minor suggestion on docstrings.

[seisman]

Suggested change

	- IGPP Earth Free-Air Anomaly Errors
	- IGPP Earth Free-Air Anomaly Uncertainty

[yvonnefroehlich]

Hm. I used the name for the upstream docs at https://www.generic-mapping-tools.org/remote-datasets/earth-faaerror.html. But I was wondering, if "uncertainty" is better, as it is used in the docstrings. Maybe we should also update the upstream docs; I can include this in PR GenericMappingTools/remote-datasets#128 if approved.

[seisman]

The GMT remote-dataset docs is inconsistenly using "error" and "uncertainty", while the officiail README file (https://topex.ucsd.edu/pub/global_grav_1min/README_V32.txt) uses "uncertainty":

grav_error_32.1.nc - uncertainty in gravity anomaly and sea surface slope, milligal or microradian, netcdf, lon-lat coordinates

[yvonnefroehlich]

Made commit GenericMappingTools/remote-datasets@5aa5e58 for changing this in the GMT remote-dataset docs.

But we stick to "error" in the GMT dataset name faaerror ?

[seisman]

I think faaerror is fine.

[seisman]

BTW, maybe change the PR title to "load_earth_free_air_anomaly: Add the 'uncertainty' parameter to return free-air anomaly errors".