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

pygmt/datasets/earth_free_air_anomaly.py

@@ -10,6 +10,7 @@
 
 import xarray as xr
 from pygmt.datasets.load_remote_dataset import _load_remote_dataset
+from pygmt.exceptions import GMTInvalidInput
 
 __doctest_skip__ = ["load_earth_free_air_anomaly"]
 
@@ -20,36 +21,42 @@
     ] = "01d",
     region: Sequence[float] | str | None = None,
     registration: Literal["gridline", "pixel", None] = None,
+    data_source: Literal["faa", "faaerror"] = "faa",
 ) -> xr.DataArray:
     r"""
     Load the IGPP Earth free-air anomaly dataset in various resolutions.
 
-    .. figure:: https://www.generic-mapping-tools.org/remote-datasets/_images/GMT_earth_faa.jpg
-       :width: 80 %
-       :align: center
+    .. list-table::
+       :widths: 50 50
+       :header-rows: 1
 
-       IGPP Earth free-air anomaly dataset.
+       * - IGPP Earth Free-Air Anomaly
+         - IGPP Earth Free-Air Anomaly Errors
+       * - .. figure:: https://www.generic-mapping-tools.org/remote-datasets/_images/GMT_earth_faa.jpg
+         - .. figure:: https://www.generic-mapping-tools.org/remote-datasets/_images/GMT_earth_faaerror.jpg
 
-    The grids are downloaded to a user data directory
-    (usually ``~/.gmt/server/earth/earth_faa/``) 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.
+    The grids are downloaded to a user data directory (usually
+    ``~/.gmt/server/earth/earth_faa/`` or ``~/.gmt/server/earth/earth_faaerror/``) the
+    first time you invoke this function. Afterwards, it will load the grid from 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_faa**\_\ *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 *@earth_faa.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="@earth_faa.cpt"``.
-
-    Refer to :gmt-datasets:`earth-faa.html` for more details about available
-    datasets, including version information and references.
+    **@earth_faa_type**\_\ *res*\[_\ *reg*] to any grid processing function or
+    plotting method. *earth_faa_type* is the GMT name for the dataset. The available
+    options are **earth_faa** and **earth_faaerror**. *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 tables (CPTs) for these datasets are *@earth_faa.cpt* and
+    *@earth_faaerror.cpt*. The dataset-specific CPT is 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="@earth_faa.cpt"`` or
+    ``cmap="@earth_faaerror.cpt"``.
+
+    Refer to :gmt-datasets:`earth-faa.html` and :gmt-datasets:`earth-faaerror.html` for
+    more details about available datasets, including version information and references.
 
     Parameters
     ----------
@@ -63,8 +70,12 @@
     registration
         Grid registration type. Either ``"pixel"`` for pixel registration or
         ``"gridline"`` for gridline registration. Default is ``None``, means
-        ``"gridline"`` for all resolutions except ``"01m"`` which is
-        ``"pixel"`` only.
+        ``"gridline"`` for all resolutions except ``"01m"`` which is ``"pixel"`` only.
+    data_source
+        Select the free air anomaly data. Available options are:
+
+        - ``"faa"``: Altimetry-based marine free-air anomaly values.
+        - ``"faaerror"``: Uncertainties to the free-air anomaly values.
 
     Returns
     -------
@@ -75,13 +86,12 @@
     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.
+    :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
     --------
@@ -93,14 +103,23 @@
     >>> grid = load_earth_free_air_anomaly(resolution="30m", registration="gridline")
     >>> # load high-resolution (5 arc-minutes) grid for a specific region
     >>> grid = load_earth_free_air_anomaly(
-    ...     resolution="05m",
-    ...     region=[120, 160, 30, 60],
-    ...     registration="gridline",
+    ...     resolution="05m", region=[120, 160, 30, 60], registration="gridline"
     ... )
     """
+    # Map data source to prefix
+    prefix = {
+        "faa": "earth_faa",
+        "faaerror": "earth_faaerror",
+    }.get(data_source)
+    if prefix is None:
+        msg = (
+            f"Invalid earth free air anomaly data source '{data_source}'. "
+            "Valid values are 'faa' and 'faaerror'."
+        )
+        raise GMTInvalidInput(msg)
     grid = _load_remote_dataset(
-        name="earth_faa",
-        prefix="earth_faa",
+        name=prefix,
+        prefix=prefix,
         resolution=resolution,
         region=region,
         registration=registration,

pygmt/datasets/load_remote_dataset.py

@@ -128,6 +128,24 @@ class GMTRemoteDataset(NamedTuple):
             "01m": Resolution("01m", registrations=["pixel"], tiled=True),
         },
     ),
+    "earth_faaerror": GMTRemoteDataset(
+        description="IGPP Earth free-air anomaly errors",
+        units="mGal",
+        extra_attributes={"horizontal_datum": "WGS84"},
+        resolutions={
+            "01d": Resolution("01d"),
+            "30m": Resolution("30m"),
+            "20m": Resolution("20m"),
+            "15m": Resolution("15m"),
+            "10m": Resolution("10m"),
+            "06m": Resolution("06m"),
+            "05m": Resolution("05m", tiled=True),
+            "04m": Resolution("04m", tiled=True),
+            "03m": Resolution("03m", tiled=True),
+            "02m": Resolution("02m", tiled=True),
+            "01m": Resolution("01m", registrations=["pixel"], tiled=True),
+        },
+    ),
     "earth_gebco": GMTRemoteDataset(
         description="GEBCO Earth relief",
         units="meters",

pygmt/helpers/caching.py

@@ -16,6 +16,7 @@ def cache_data():
         "@earth_day_01d",
         "@earth_dist_01d",
         "@earth_faa_01d_g",
+        "@earth_faaerror_01d_g",
         "@earth_gebco_01d_g",
         "@earth_gebcosi_01d_g",
         "@earth_gebcosi_15m_p",
@@ -51,6 +52,7 @@ def cache_data():
         "@N30E090.earth_age_01m_g.nc",
         "@N00W030.earth_dist_01m_g.nc",
         "@N00W030.earth_faa_01m_p.nc",
+        "@N00W030.earth_faaerror_01m_p.nc",
         "@N00W030.earth_geoid_01m_g.nc",
         "@S30W060.earth_mag_02m_p.nc",
         "@S30W120.earth_mag4km_02m_p.nc",

pygmt/tests/test_datasets_earth_free_air_anomaly.py

@@ -52,3 +52,54 @@ def test_earth_faa_01m_default_registration():
     npt.assert_allclose(data.coords["lon"].data.max(), -9.00833333)
     npt.assert_allclose(data.min(), -49.225, atol=0.025)
     npt.assert_allclose(data.max(), 115.0, atol=0.025)
+
+
+def test_earth_faaerror_01d():
+    """
+    Test some properties of the free air anomaly error 01d data.
+    """
+    data = load_earth_free_air_anomaly(resolution="01d", data_source="faaerror")
+    assert data.name == "z"
+    assert data.attrs["long_name"] == "faaerror (mGal)"
+    assert data.attrs["description"] == "IGPP Earth free-air anomaly errors"
+    assert data.attrs["units"] == "mGal"
+    assert data.attrs["horizontal_datum"] == "WGS84"
+    assert data.shape == (181, 361)
+    assert data.gmt.registration == 0
+    npt.assert_allclose(data.lat, np.arange(-90, 91, 1))
+    npt.assert_allclose(data.lon, np.arange(-180, 181, 1))
+    npt.assert_allclose(data.min(), 0.0, atol=0.04)
+    npt.assert_allclose(data.max(), 49.16, atol=0.04)
+
+
+def test_earth_faaerror_01d_with_region():
+    """
+    Test loading low-resolution earth free air anomaly error with 'region'.
+    """
+    data = load_earth_free_air_anomaly(
+        resolution="01d", region=[-10, 10, -5, 5], data_source="faaerror"
+    )
+    assert data.shape == (11, 21)
+    assert data.gmt.registration == 0
+    npt.assert_allclose(data.lat, np.arange(-5, 6, 1))
+    npt.assert_allclose(data.lon, np.arange(-10, 11, 1))
+    npt.assert_allclose(data.min(), 0.72, atol=0.04)
+    npt.assert_allclose(data.max(), 21.04, atol=0.04)
+
+
+def test_earth_faaerror_01m_default_registration():
+    """
+    Test that the grid returned by default for the 1 arc-minute resolution has a "pixel"
+    registration.
+    """
+    data = load_earth_free_air_anomaly(
+        resolution="01m", region=[-10, -9, 3, 5], data_source="faaerror"
+    )
+    assert data.shape == (120, 60)
+    assert data.gmt.registration == 1
+    npt.assert_allclose(data.coords["lat"].data.min(), 3.008333333)
+    npt.assert_allclose(data.coords["lat"].data.max(), 4.991666666)
+    npt.assert_allclose(data.coords["lon"].data.min(), -9.99166666)
+    npt.assert_allclose(data.coords["lon"].data.max(), -9.00833333)
+    npt.assert_allclose(data.min(), 0.40, atol=0.04)
+    npt.assert_allclose(data.max(), 13.36, atol=0.04)