isGrafLab: Irregular Surface GRAvity Field LABoratory
isGrafLab (Irregular Surface GRAvity Field LABoratory) is a modified version of GrafLab that allows accurate and fast computation of functionals of the geopotential at dense grids on irregular surfaces such as the Earth's surface. It employs the highly efficient lumped coefficients approach for surface spherical harmonic synthesis of the functionals and their radial derivatives at regular surfaces (sphere or ellipsoid of revolution), and the Taylor series expansions to continue the functionals to the irregular surface. All the other options available in GrafLab, such as three approaches to compute Legendre's functions, the graphical user interface or data plotting, are also available in isGrafLab.
Bucha, B., Janák, J. (2014). A MATLAB-based graphical user interface program for computing functionals of the geopotential up to ultra-high degrees and orders: Efficient computation at irregular surfaces. Computers & Geosciences 66, 219-227. http://doi.org/10.1016/j.cageo.2014.02.005.