Inv_Stokes

Transform Geoid undulations to gravity anomalies via the inverse Stokes formula

This function takes a grid of geoid undulations and transforms them into gravity anomaly values using a banded 2D-FFT method to evaluate the inverse Stokes integral.

This function is best suited to be used in a remove-compute-restore type process (i.e. N should be a grid of residual geoid undulations are subtraction of a long wavelength global model). It is also beneficial to input N with 100% zero padding to avoid cyclic convolutions.

Gravity_Anom=Inv_Stokes(Longm,Latm,N,res)

The inputs are as follows:

- N is an n x m geoid undulation grid
- Longm is a grid of longitude values for each grid node in N (in Degrees)
- Latm is a grid of latitude values for each grid node in N (in Degrees)
- res is the resolution of the N grid (i.e. one arc minute grid would have res=1/60) (in Degrees)

The code is an implementation of the formulas provided in;
Hirt, C., Featherstone, W.E. and Claessens, S.J., 2011. On the accurate numerical evaluation of geodetic convolution integrals. Journal of Geodesy, 85(8), pp.519-538.