"""
Function to download the EGM2008 Global Earth Geoid from the GMT data server,
and load as :class:`xarray.DataArray`.
The grids are available in various resolutions.
"""
from pygmt.datasets.load_remote_dataset import _load_remote_dataset
from pygmt.helpers import kwargs_to_strings
__doctest_skip__ = ["load_earth_geoid"]
[docs]@kwargs_to_strings(region="sequence")
def load_earth_geoid(resolution="01d", region=None, registration=None):
r"""
Load the EGM2008 Global Earth Geoid in various resolutions.
The grids are downloaded to a user data directory
(usually ``~/.gmt/server/earth/earth_geoid/``) the first time you invoke
this function. Afterwards, it will load the grid from the data directory.
So you'll need an internet connection the first time around.
These grids can also be accessed by passing in the file name
**@earth_geoid**\_\ *res*\[_\ *reg*] to any grid plotting/processing
function. *res* is the grid resolution (see below), and *reg* is grid
registration type (**p** for pixel registration or **g** for gridline
registration).
Refer to :gmt-datasets:`earth-geoid.html` for more details.
Parameters
----------
resolution : str
The grid resolution. The suffix ``d`` and ``m`` stand for
arc-degrees and arc-minutes. It can be ``"01d"``, ``"30m"``,
``"20m"``, ``"15m"``, ``"10m"``, ``"06m"``, ``"05m"``, ``"04m"``,
``"03m"``, ``"02m"``, or ``"01m"``.
region : str or list
The subregion of the grid to load, in the form of a list
[*xmin*, *xmax*, *ymin*, *ymax*] or a string *xmin/xmax/ymin/ymax*.
Required for grids with resolutions higher than 5
arc-minutes (i.e., ``"05m"``).
registration : str
Grid registration type. Either ``"pixel"`` for pixel registration or
``"gridline"`` for gridline registration. Default is ``"gridline"``.
Returns
-------
grid : :class:`xarray.DataArray`
The Earth geoid grid. Coordinates are latitude and
longitude in degrees. Units are in meters.
Note
----
The :class:`xarray.DataArray` grid doesn't support slice operation, for
Earth geoid grids with resolutions of 5 arc-minutes or higher,
which are stored as smaller tiles.
Examples
--------
>>> from pygmt.datasets import load_earth_geoid
>>> # load the default grid (gridline-registered 1 arc-degree grid)
>>> grid = load_earth_geoid()
>>> # load the 30 arc-minutes grid with "gridline" registration
>>> grid = load_earth_geoid(resolution="30m", registration="gridline")
>>> # load high-resolution (5 arc-minutes) grid for a specific region
>>> grid = load_earth_geoid(
... resolution="05m",
... region=[120, 160, 30, 60],
... registration="gridline",
... )
"""
grid = _load_remote_dataset(
dataset_name="earth_geoid",
dataset_prefix="earth_geoid_",
resolution=resolution,
region=region,
registration=registration,
)
return grid