"""
Function to download the Mercury relief dataset from the GMT data server, and load as
:class:`xarray.DataArray`.
The grids are available in various resolutions.
"""
from typing import Literal
from pygmt.datasets.load_remote_dataset import _load_remote_dataset
from pygmt.helpers import kwargs_to_strings
__doctest_skip__ = ["load_mercury_relief"]
[docs]
@kwargs_to_strings(region="sequence")
def load_mercury_relief(
resolution="01d",
region=None,
registration: Literal["gridline", "pixel", None] = None,
):
r"""
Load the Mercury relief dataset in various resolutions.
.. figure:: https://www.generic-mapping-tools.org/remote-datasets/_images/GMT_mercury_relief.jpg
:width: 80%
:align: center
Mercury relief dataset.
The grids are downloaded to a user data directory (usually
``~/.gmt/server/mercury/mercury_relief/``) 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
**@mercury_relief**\_\ *res*\[_\ *reg*] to any grid processing function or plotting
method. *res* is the grid resolution (see below), and *reg* is the grid registration
type (**p** for pixel registration or **g** for gridline registration).
The default color palette table (CPT) for this dataset is *@mercury_relief.cpt*.
It's implicitly used when passing in the file name of the dataset to any grid
plotting method if no CPT is explicitly specified. When the dataset is loaded and
plotted as an :class:`xarray.DataArray` object, the default CPT is ignored, and
GMT's default CPT (*turbo*) is used. To use the dataset-specific CPT, you need to
explicitly set ``cmap="@mercury_relief.cpt"``.
Refer to :gmt-datasets:`mercury-relief.html` for more details about available
datasets, including version information and references.
Parameters
----------
resolution : str
The grid resolution. The suffix ``d``, ``m`` and ``s`` stand for arc-degrees,
arc-minutes and arc-seconds. It can be ``"01d"``, ``"30m"``, ``"20m"``,
``"15m"``, ``"10m"``, ``"06m"``, ``"05m"``, ``"04m"``, ``"03m"``, ``"02m"``,
``"01m"``, and ``"56s"``.
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
Grid registration type. Either ``"pixel"`` for pixel registration or
``"gridline"`` for gridline registration. Default is ``None``, means
``"gridline"`` for all resolutions except for ``"56s"`` which is ``"pixel"``
only.
Returns
-------
grid : :class:`xarray.DataArray`
The Mercury relief grid. Coordinates are latitude and longitude in degrees.
Relief is in meters.
Note
----
The registration and coordinate system type of the returned
:class:`xarray.DataArray` grid can be accessed via the GMT accessors (i.e.,
``grid.gmt.registration`` and ``grid.gmt.gtype`` respectively). However, these
properties may be lost after specific grid operations (such as slicing) and will
need to be manually set before passing the grid to any PyGMT data processing or
plotting functions. Refer to :class:`pygmt.GMTDataArrayAccessor` for detailed
explanations and workarounds.
Examples
--------
>>> from pygmt.datasets import load_mercury_relief
>>> # load the default grid (gridline-registered 1 arc-degree grid)
>>> grid = load_mercury_relief()
>>> # load the 30 arc-minutes grid with "gridline" registration
>>> grid = load_mercury_relief(resolution="30m", registration="gridline")
>>> # load high-resolution (5 arc-minutes) grid for a specific region
>>> grid = load_mercury_relief(
... resolution="05m",
... region=[120, 160, 30, 60],
... registration="gridline",
... )
"""
grid = _load_remote_dataset(
dataset_name="mercury_relief",
dataset_prefix="mercury_relief_",
resolution=resolution,
region=region,
registration=registration,
)
return grid