Gravitational field maps and navigational errors

It has been proposed to use gravitational field maps to correct navigational errors inherent in some navigational systems presently in use on unmanned underwater vehicles (UUV) and that such a technology might form the basis for a new UUV navigational system. However, the accuracy and usefulness of the navigational solution depends, among other things, on the accuracy of the gravitational field maps. Since gravitational fields are generally sparsely and irregularly sampled, mapping algorithms must be used to construct the field maps. To assess the impact of field maps computed from sparse sets of data on the accuracy of the navigational solution, the kriging algorithm is used to compute field maps with various grid spacings from both simulated and measured field data. Then position and bearing errors are simulated and the various field maps are used to obtain corrected navigational fixes. To assess the impact of the density of the field data on the accuracy of the navigational fix, the simulated data are sub-sampled and the process is repeated. Numerical results are shown that demonstrate some of the effects of grid spacing and data density on the accuracy of the navigational fix and that gravitational field maps may be used to provide a very accurate navigational fix.