Calculate the spherical harmonic coefficients of a spherical cap.
coef = SphericalCapCoef (theta, lmax)
coef : float, dimension(lmax+1) : The zonal spherical harmonic coefficients of a spherical cap centered over the north pole.
theta : float : The angular radius of the spherical cap in radians.
lmax : integer : The maximum spherical harmonic degree to calculate the spherical harmonic coefficients.
SphericalCapCoef will calculate the spherical harmonic coefficients of a spherical cap centered over the north pole. The zonal coefficients, returned in the array coef, are normalized such that the degree-0 term is 1, and are to be used with either the geodesy 4-pi normalized or orthonormalized spherical harmonics.