pygmt.datasets.load_earth_geoid

pygmt.datasets.load_earth_geoid(resolution='01d', region=None, registration='gridline')

Load the EGM2008 Earth geoid dataset in various resolutions.

EGM2008 Earth geoid dataset.

This function downloads the dataset from the GMT data server, caches it in a user data directory (usually ~/.gmt/server/earth/earth_geoid/), 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 dataset can also be accessed by specifying a file name in any grid processing function or plotting method, using the following file name format: @earth_geoid_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., @earth_geoid_01d), the gridline-registered grid will be loaded for grid proccessing functions and the pixel-registered grid will be loaded for plotting functions. If res is also omitted (i.e., @earth_geoid), GMT automatically selects a suitable resolution based on the current region and projection settings.

Refer to https://www.generic-mapping-tools.org/remote-datasets/earth-geoid.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'], default: 'gridline') – Grid registration type. Either "pixel" for pixel registration or "gridline" for gridline registration.

Return type:

DataArray

Returns:

grid – The Earth geoid grid. Coordinates are latitude and longitude in degrees. Units are in meters.

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_geoid
>>> # Load the default grid (gridline-registered 1 arc-degree grid)
>>> grid = load_earth_geoid()
>>> # Load the 30 arc-minutes grid with "gridline" registration
>>> grid = load_earth_geoid(resolution="30m", registration="gridline")
>>> # Load high-resolution (5 arc-minutes) grid for a specific region
>>> grid = load_earth_geoid(
...     resolution="05m",
...     region=[120, 160, 30, 60],
...     registration="gridline",
... )