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*The current version of SHTOOLS is 4.0 (released December 16, 2016)*

# What is SHTOOLS?

SHTOOLS is an archive of Fortran 95 and Python software that can be used to perform spherical harmonic transforms and reconstructions, rotations of data expressed in spherical harmonics, and multitaper spectral analyses on the sphere.

SHTOOLS is extremely versatile:

- It can accommodate any standard normalization of the spherical harmonic functions ("geodesy" 4π normalized, Schmidt semi-normalized, orthonormalized, and unnormalized).
- Both real and complex spherical harmonics are supported.
- Spherical harmonic transforms are calculated by exact quadrature rules using either the sampling theorem of
*Driscoll and Healy*(1994) where data are equally sampled (or spaced) in latitude and longitude, or Gauss-Legendre quadrature. - One can choose to use or exclude the Condon-Shortley phase factor of (-1)
^{m}with the associated Legendre functions. - The spherical harmonic transforms are accurate to approximately degree 2800, corresponding to a spatial resolution of better than 4 arc minutes.
- The fortran routines are OpenMP compatible and OpenMP thread-safe.
- Routines are included for performing localized multitaper spectral analyses.
- Routines are included for performing standard gravity and magnetic field calculations, such as computation of the geoid and the determination of the potential associated with finite-amplitude topography.
- The routines are fast. Spherical harmonic transforms and reconstructions take on the order of 1 second for bandwidths less than 600 and about 3 minutes for bandwidths close to 2800.

# How do I install SHTOOLS?

The Python components of SHTOOLS can be installed using the Python package manager `pip`. In a unix terminal, you need only to execute the following command:

pip install pyshtools

To install the Fortran 95 components for use in your Fortran programs, installation can be as simple as executing the commands:

make fortran

make fortran-mp# (for OpenMP)

The most recent release of SHTOOLS can always be downloaded from GitHub. Full installation instructions can be found here, and additional information can be found on the GitHub wiki. You can keep up to date by following SHTOOLS on Twitter.

# How do I use SHTOOLS?

SHTOOLS can be invoked in any Fortran 95, Python 2, or Python 3 program. The core software is written in Fortran 95, and Python wrappers allow simple access to the fortran-compiled routines. A variety of Python notebooks and example files are included that demonstrate the major features of the library.

SHTOOLS is open source (revised BSD license) and makes use of the freely available Fourier transform package FFTW and the linear algebra packages LAPACK and BLAS.

Laboratoire Lagrange | Observatoire de la Côte d'Azur | © 2016 SHTOOLS |