pygmt.datasets.load_earth_free_air_anomaly

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

Load an Earth Free-Air Anomaly grid in various resolutions.

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.

These grids can also be accessed by passing in the file name @earth_faa_res[_reg] to any grid plotting/processing function. res is the grid resolution (see below), and reg is grid registration type (p for pixel registration or g for gridline registration).

Refer to https://www.generic-mapping-tools.org/remote-datasets/earth-faa.html for more details.

Parameters

  • resolution (str) – The grid resolution. The suffix d and m stand for arc-degrees and arc-minutes. It can be "01d", "30m", "20m", "15m", "10m", "06m", "05m", "04m", "03m", "02m", or "01m".

  • region (str or list) – The subregion of the grid to load, in the form of a list [xmin, xmax, ymin, ymax] or a string xmin/xmax/ymin/ymax. Required for grids with resolutions higher than 5 arc-minutes (i.e., "05m").

  • registration (str) – Grid registration type. Either "pixel" for pixel registration or "gridline" for gridline registration. Default is "gridline" for all resolutions except "01m" which is "pixel" only.

Returns

grid (xarray.DataArray) – The Earth free-air anomaly grid. Coordinates are latitude and longitude in degrees. Units are in mGal.

Note

The xarray.DataArray grid doesn’t support slice operation, for Earth free-air anomaly with resolutions of 5 arc-minutes or higher, which are stored as smaller tiles.

Examples

>>> from pygmt.datasets import load_earth_free_air_anomaly
>>> # load the default grid (gridline-registered 1 arc-degree grid)
>>> grid = load_earth_free_air_anomaly()
>>> # load the 30 arc-minutes grid with "gridline" registration
>>> 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",
... )