pygmt.grdfill(grid, outgrid=None, **kwargs)[source]

Fill blank areas from a grid file.

Read a grid that presumably has unfilled holes that the user wants to fill in some fashion. Holes are identified by NaN values but this criteria can be changed via the no_data parameter. There are several different algorithms that can be used to replace the hole values.

Full option list at


  • A = mode

  • N = no_data

  • R = region

  • V = verbose

  • grid (str or xarray.DataArray) –

    Name of the input grid file or the grid loaded as a xarray.DataArray object.

    For reading a specific grid file format or applying basic data operations, see for the available modifiers.

  • outgrid (str | None, default: None) – Name of the output netCDF grid file. If not specified, will return an xarray.DataArray object. For writing a specific grid file format or applying basic data operations to the output grid, see for the available modifiers.

  • mode (str) – Specify the hole-filling algorithm to use. Choose from c for constant fill and append the constant value, n for nearest neighbor (and optionally append a search radius in pixels [default radius is \(r^2 = \sqrt{ X^2 + Y^2 }\), where (X,Y) are the node dimensions of the grid]), or s for bicubic spline (optionally append a tension parameter [Default is no tension]).

  • no_data (float) – Set the node value used to identify a point as a member of a hole [Default is NaN].

  • region (str or list) – xmin/xmax/ymin/ymax[+r][+uunit]. Specify the region of interest.

  • verbose (bool or str) –

    Select verbosity level [Default is w], which modulates the messages written to stderr. Choose among 7 levels of verbosity:

    • q - Quiet, not even fatal error messages are produced

    • e - Error messages only

    • w - Warnings [Default]

    • t - Timings (report runtimes for time-intensive algorithms)

    • i - Informational messages (same as verbose=True)

    • c - Compatibility warnings

    • d - Debugging messages


ret (xarray.DataArray or None) – Return type depends on whether the outgrid parameter is set:

  • xarray.DataArray if outgrid is not set

  • None if outgrid is set (grid output will be stored in file set by outgrid)


>>> import pygmt
>>> # Load a bathymetric grid with missing data
>>> earth_relief_holes = pygmt.datasets.load_sample_data(name="earth_relief_holes")
>>> # Perform grid filling operations on the sample grid
>>> # Set all empty values to "20"
>>> filled_grid = pygmt.grdfill(grid=earth_relief_holes, mode="c20")