"""
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 collections.abc import Sequence
from typing import Literal
import xarray as xr
from pygmt.datasets.load_remote_dataset import _load_remote_dataset
__doctest_skip__ = ["load_mercury_relief"]
[docs]
def load_mercury_relief(
resolution: Literal[
"01d",
"30m",
"20m",
"15m",
"10m",
"06m",
"05m",
"04m",
"03m",
"02m",
"01m",
"56s",
] = "01d",
region: Sequence[float] | str | None = None,
registration: Literal["gridline", "pixel", None] = None,
) -> xr.DataArray:
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.
This function downloads the dataset from the GMT data server, caches it in a user
data directory (usually ``~/.gmt/server/mercury/mercury_relief/``), and load the
dataset as an :class:`xarray.DataArray`. An internet connection is required the
first time around, but subsequent calls will load the dataset from the local data
directory.
The dataset can also be accessed by specifying a file name in any grid processing
function or plotting method, using the following file name format:
**@mercury_relief**\_\ *res*\_\ *reg*. *res* is the grid resolution; *reg* is the
grid registration type (**p** for pixel registration, **g** for gridline
registration). If *reg* is omitted (e.g., ``@mercury_relief_01d``), the
gridline-registered grid will be loaded for grid processing functions and the
pixel-registered grid will be loaded for plotting functions. If *res* is also
omitted (i.e., ``@mercury_relief``), GMT automatically selects a suitable resolution
based on the current region and projection settings.
This dataset comes with a color palette table (CPT) file, ``@mercury_relief.cpt``.
To use the dataset-specific CPT when plotting the dataset, explicitly set
``cmap="@mercury_relief.cpt"``, otherwise GMT's default CPT (*turbo*) will be used.
If the dataset is referenced by the file name in a grid plotting method, the
dataset-specific CPT file is used automatically unless another CPT is specified.
Refer to :gmt-datasets:`mercury-relief.html` for more details about available
datasets, including version information and references.
Parameters
----------
resolution
The grid resolution. The suffix ``d``, ``m`` and ``s`` stand for arc-degrees,
arc-minutes and arc-seconds. Note that ``"56s"`` refers to a resolution of
56.25 arc-seconds.
region
The subregion of the grid to load, in the form of a sequence [*xmin*, *xmax*,
*ymin*, *ymax*] or an ISO country code. 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``, which means
``"gridline"`` for all resolutions except for ``"56s"`` which is ``"pixel"``
only.
Returns
-------
grid
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* accessor. Refer to
:class:`pygmt.GMTDataArrayAccessor` for detailed explanations and limitations.
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(
name="mercury_relief",
prefix="mercury_relief",
resolution=resolution,
region=region,
registration=registration,
)
return grid