If you want to learn how to incorporate shtools routines in your fortran programs, the following example programs are a good starting point to see shtools in action.
Folder Description
SHCilmPlus/ Demonstration of how to expand spherical harmonic files into gridded maps using the GLQ routines, and how to compute the gravity field resulting from finite amplitude surface relief.
SHExpandDH/ Demonstration of how to expand a grid that is equally sampled in latitude and longitude into spherical harmonics using the sampling theorem of Driscoll and Healy (1994).
SHExpandLSQ/ Demonstration of how to expand a set of irregularly sampled data points in latitude and longitude into spherical harmonics by use of a least squares inversion.
SHMag/ Demonstration of how to expand scalar magnetic potential spherical harmonic coefficients into their three vector components and total field.
MarsCrustalThickness/ Demonstration of how to compute a crustal thickness map of Mars.
SHRotate/ Demonstration of how to determine the spherical harmonic coefficients for a body that is rotated with respect to its initial configuration.
SHLocalizedAdmitCorr/ Demonstration of how to calculate localized admittance and correlation spectra for a given set of gravity and topography spherical harmonic coefficients.
TimingAccuracy/ Test programs that calculate the time required to perform the GLQ and DH spherical harmonic transforms and reconstructions and the accuracy of these operations.