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SHTOOLS/SHTOOLS: Version 4.6.1

Mark Wieczorek; MMesch; Ilya Oshchepkov; Elliott Sales de Andrade; xoviat; Benda Xu; Akihisa Hattori; Stefan Schröder; Katrin Leinweber; Andrew Walker; Aaryaman Vasishta

Version 4.6 New extended grids

All grid formats now allow to compute the redundant values at 360 E longitude (GLQ and DH), as well as at 90 S (DH only). These extended grids are now the default in pyshtools, but remain optional in the Fortran 95 routines. The use of extended grids is controlled by the optional argument extend. The purpose of these extended grids is to better integrate with the plotting routines that require these points (i.e.., Cartopy and pygmt).

Improved plotting and map projections

The plotting routine SHGrid.plot() has been refactored to allow support for projections using Cartopy and pygmt.

  • An incorrect 0.5 pixel offset was fixed when plotting grids via matplotlib, and grids now correctly plot both 0 and 360 degrees using the new "extended" grids of SHGrid.
  • Support was added for Cartopy projections, by specifying: SHGrid.plot(projection=ccrs.ProjectionName()).
  • The argument colorbar now takes the options 'top', 'bottom', 'left' or 'right'.
  • Improved plotting and placement of colorbars. New optional arguments include cb_label for labels, cb_ylabel for a label on the y axis of the colorbar, cb_tick_interval for specifying the major tick interval, cb_minor_tick_interval for specifying minor tick intervals, cb_triangles for plotting upper/lower limit triangles at the ends of the colorbar, cb_width to specify the colorbar width, and cb_offset to override the default spacing between the map and colorbar.
  • Improved colormap handling: New optional arguments include cmap_limits to specify the lower and upper bounds of the data, as well as an interval for constant color intervals, and cmap_reverse to reverse the colormap.
  • Improved handling of ticks and annotations: The optional argument ticks specifies which ticks and annotations to show, using a syntax from the generic mapping tools (i.e., 'WSen').
  • Experimental support for pygmt using the routine SHGrid.plotgmt(). This function takes nearly the same arguments as plot(). As soon as pygmt implements projection classes (https://github.com/GenericMappingTools/pygmt/pull/379), this will be incorporated into the plot function in the same manner as Cartopy was.
  • All gravity, magnetics, tensor, localization windows and slepian function plotting routines incorporate these changes.
  • Added a new introductory notebook that shows how to use all features of the plot() function.
Improved integration with xarray DataArrays, xarray DataSets, and netcdf files
  • Added the methods to_netcdf() and from_netcdf() to the SHCoeffs, SHGravCoeffs and SHMagCoeffs classes.
  • Added the method SHGrid.from_xarray() to initialize a grid from an xarray DataArray.
  • Added improved descriptive attributes for netcdf files that mirror these conventions.
  • Added the method SHGeoid.to_xarray() to export an xarray DataArray and to_netcdf() to export a netcdf object readable by the generic mapping tools.
  • Added the methods SHGravGrid.to_xarray() and SHMagGrid.to_xarray() to export all gridded data (radial, theta, phi, total, and potential) as an xarray DataSet.
  • Added the methods SHGravTensor.to_xarray() and SHMagTensor.to_xarray()to export all gridded data (Vxx, invariants, eigenvalues) as an xarray DataSet.
Gravity routine improvements
  • Added the method SHGravCoeffs.center_of_mass to calculate the center of mass of a body.
  • Added the method SHGravCoeffs.inertia_tensor() to calculate the moment of inertia tensor.
  • Added the Earth dynamical flattening constant H (IERS Conventions 2010) to the constant module.
  • The read_icgem_gfc() function was extended with the option encoding as some models in ICGEM are not in UTF-8.
  • Addded the method centroid() to the class SHCoeffs. The centroid is computed as the center of mass of a homogeneous object.
Other changes
  • New methods SHGrid.to_real() and SHGrid.to_imag() return the real and imaginary components of a complex SHGrid instance.
  • Added an optional argument copy to SHCoeffs.pad().
  • Fixed bugs in the Fortran code of PlBar_d1 and PlON_d1 when calculating the Legendre polynomials at the north and south pole.
  • Spherical harmonic coefficients can be read remotely by specifying a URL as the filename. This functionality uses requests.get(), and has been implemented in the function shread() and the SHCoeffs method from_file().
  • Fixed a bug in the fortran code of Curve2Mask. As part of this fix, the optional parameter centralmeridian has been removed as it is no longer required. The longitudes of the curve can possess values from -360 to 720 degrees, and the routine searches for discontinuities that may occur between two successive points as the longitudes pass from 360 to 0, or -180 to 180 degrees.

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