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Add function to load Black Marble dataset (#3469)
Function to load the `@earth_night_` NASA Black Marble mosaic RGB images stored as GeoTIFF files. * Add entry for datasets.load_black_marble in doc/api/index.rst * Add unit tests for load_black_marble * Import rioxarray to register rio accessor * Add @earth_day_01d to pygmt/helpers/caching.py
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""" | ||
Function to download the NASA Black Marble image datasets from the GMT data server, and | ||
load as :class:`xarray.DataArray`. | ||
The images are available in various resolutions. | ||
""" | ||
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import contextlib | ||
from collections.abc import Sequence | ||
from typing import Literal | ||
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import xarray as xr | ||
from pygmt.datasets.load_remote_dataset import _load_remote_dataset | ||
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with contextlib.suppress(ImportError): | ||
# rioxarray is needed to register the rio accessor | ||
import rioxarray # noqa: F401 | ||
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__doctest_skip__ = ["load_black_marble"] | ||
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def load_black_marble( | ||
resolution: Literal[ | ||
"01d", | ||
"30m", | ||
"20m", | ||
"15m", | ||
"10m", | ||
"06m", | ||
"05m", | ||
"04m", | ||
"03m", | ||
"02m", | ||
"01m", | ||
"30s", | ||
] = "01d", | ||
region: Sequence[float] | str | None = None, | ||
) -> xr.DataArray: | ||
r""" | ||
Load NASA Black Marble images in various resolutions. | ||
.. figure:: https://www.generic-mapping-tools.org/remote-datasets/_images/GMT_earth_daynight.jpg | ||
:width: 80% | ||
:align: center | ||
Earth day/night dataset. | ||
The images are downloaded to a user data directory (usually | ||
``~/.gmt/server/earth/earth_night/``) the first time you invoke this function. | ||
Afterwards, it will load the image from the data directory. So you'll need an | ||
internet connection the first time around. | ||
These images can also be accessed by passing in the file name | ||
**@earth_night**\_\ *res* to any image processing function or plotting method. *res* | ||
is the image resolution (see below). | ||
Refer to :gmt-datasets:`earth-daynight.html` for more details about available | ||
datasets, including version information and references. | ||
Parameters | ||
---------- | ||
resolution | ||
The image resolution. The suffix ``d``, ``m``, and ``s`` stand for arc-degree, | ||
arc-minute, and arc-second. | ||
region | ||
The subregion of the image to load, in the form of a sequence [*xmin*, *xmax*, | ||
*ymin*, *ymax*]. | ||
Returns | ||
------- | ||
image | ||
The NASA Black Marble image. Coordinates are latitude and longitude in degrees. | ||
Note | ||
---- | ||
The registration and coordinate system type of the returned | ||
:class:`xarray.DataArray` image can be accessed via the GMT accessors (i.e., | ||
``image.gmt.registration`` and ``image.gmt.gtype`` respectively). However, these | ||
properties may be lost after specific image operations (such as slicing) and will | ||
need to be manually set before passing the image to any PyGMT data processing or | ||
plotting functions. Refer to :class:`pygmt.GMTDataArrayAccessor` for detailed | ||
explanations and workarounds. | ||
Examples | ||
-------- | ||
>>> from pygmt.datasets import load_black_marble | ||
>>> # load the default image (pixel-registered 1 arc-degree image) | ||
>>> image = load_black_marble() | ||
""" | ||
image = _load_remote_dataset( | ||
name="earth_night", | ||
prefix="earth_night", | ||
resolution=resolution, | ||
region=region, | ||
registration="pixel", | ||
) | ||
# If rioxarray is installed, set the coordinate reference system | ||
if hasattr(image, "rio"): | ||
image = image.rio.write_crs(input_crs="OGC:CRS84") | ||
return image |
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""" | ||
Test basic functionality for loading Black Marble datasets. | ||
""" | ||
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import numpy as np | ||
import numpy.testing as npt | ||
from pygmt.datasets import load_black_marble | ||
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def test_black_marble_01d(): | ||
""" | ||
Test some properties of the Black Marble 01d data. | ||
""" | ||
data = load_black_marble(resolution="01d") | ||
assert data.name == "z" | ||
assert data.long_name == "black_marble" | ||
assert data.attrs["horizontal_datum"] == "WGS84" | ||
assert data.attrs["description"] == "NASA Night Images" | ||
assert data.shape == (3, 180, 360) | ||
assert data.dtype == "uint8" | ||
assert data.gmt.registration == 1 | ||
assert data.gmt.gtype == 1 | ||
npt.assert_allclose(data.y, np.arange(89.5, -90.5, -1)) | ||
npt.assert_allclose(data.x, np.arange(-179.5, 180.5, 1)) | ||
npt.assert_allclose(data.min(), 3, atol=1) | ||
npt.assert_allclose(data.max(), 174, atol=1) | ||
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def test_black_marble_01d_with_region(): | ||
""" | ||
Test loading low-resolution Black Marble with 'region'. | ||
""" | ||
data = load_black_marble(resolution="01d", region=[-10, 10, -5, 5]) | ||
assert data.shape == (3, 10, 20) | ||
assert data.dtype == "uint8" | ||
assert data.gmt.registration == 1 | ||
assert data.gmt.gtype == 1 | ||
npt.assert_allclose(data.y, np.arange(4.5, -5.5, -1)) | ||
npt.assert_allclose(data.x, np.arange(-9.5, 10.5, 1)) | ||
npt.assert_allclose(data.min(), 3, atol=1) | ||
npt.assert_allclose(data.max(), 40, atol=1) |