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 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_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",
... )