pygmt.datasets.load_earth_deflection

pygmt.datasets.load_earth_deflection(resolution='01d', region=None, registration=None, component='east')[source]

Load the IGPP Earth east-west and north-south deflection datasets in various resolutions.

IGPP Earth east-west deflection

IGPP Earth north-south deflection
https://www.generic-mapping-tools.org/remote-datasets/_images/GMT_earth_edefl.jpg
https://www.generic-mapping-tools.org/remote-datasets/_images/GMT_earth_ndefl.jpg

This function downloads the dataset from the GMT data server, caches it in a user data directory (usually ~/.gmt/server/earth/earth_edefl/ and ~/.gmt/server/earth/earth_ndefl/), and load the dataset as an xarray.DataArray. An internet connection is required the first time around, but subsequent calls will load the dataset from the local data directory.

The datasets can also be accessed by specifying a file name in any grid processing function or plotting method, using the following file name format: @earth_defl_type_res_reg. earth_defl_type is the GMT name for the dataset. The available options are earth_edefl and earth_ndefl; 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., @earth_edefl_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., @earth_edefl), GMT automatically selects a suitable resolution based on the current region and projection settings.

This dataset comes with a color palette table (CPT) file, @earth_defl.cpt. To use the dataset-specific CPT when plotting the dataset, explicitly set cmap="@earth_defl.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 https://www.generic-mapping-tools.org/remote-datasets/earth-edefl.html and https://www.generic-mapping-tools.org/remote-datasets/earth-ndefl.html for more details about available datasets, including version information and references.

Parameters:

  • resolution (Literal['01d', '30m', '20m', '15m', '10m', '06m', '05m', '04m', '03m', '02m', '01m'], default: '01d') – The grid resolution. The suffix d and m stand for arc-degrees and arc-minutes.

  • region (Sequence[float] | str | None, default: None) – 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 (Literal['gridline', 'pixel', None], default: None) – Grid registration type. Either "pixel" for pixel registration or "gridline" for gridline registration. Default is None, which means "gridline" for all resolutions except "01m" which is "pixel" only.

  • component (Literal['east', 'north'], default: 'east') – By default, the east-west deflection (component="east") is returned, set component="north" to return the north-south deflection.

Return type:

DataArray

Returns:

grid – The Earth east-west or north-south deflection grid. Coordinates are latitude and longitude in degrees. Deflection values are in micro-radians, where positive (negative) values indicate a deflection to the east or north (west or south).

Note

The registration and coordinate system type of the returned 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 pygmt.GMTDataArrayAccessor for detailed explanations and workarounds.

Examples

>>> from pygmt.datasets import load_earth_deflection
>>> # Load the default grid for east-west deflection (gridline-registered
>>> # 1 arc-degree grid)
>>> grid = load_earth_deflection()
>>> # Load the default grid for north-south deflection
>>> grid = load_earth_deflection(component="north")
>>> # Load the 30 arc-minutes grid with "gridline" registration
>>> grid = load_earth_deflection(resolution="30m", registration="gridline")
>>> # Load high-resolution (5 arc-minutes) grid for a specific region
>>> grid = load_earth_deflection(
...     resolution="05m", region=[120, 160, 30, 60], registration="gridline"
... )