1. A method for determining the orientation and location of a first sensor on a platform having a location and orientation, said first sensor tracking remote objects for purposes of gridlock and registration, said method comprising the steps of: generating first, second, third, and fourth local sensor signals representing at least first, second, third and fourth noncoplanar remote object positions, respectively, in a local coordinate system; acquiring first, second, third, and fourth remote external signals representing the positions of said first, second, third, and fourth objects in an external coordinate system which is not congruent with said local coordinate system; taking the differences between said first local sensor signal and said second local sensor signal, said third local sensor signal, and said fourth local sensor signal, to thereby generate a set of first, second, and third translationally invariant local pseudomeasurements; taking the difference between said first remote external signal and said second remote external signal, said third remote external signal, and said fourth remote external signal, to thereby generate a set of first, second, and third translationally invariant remote pseudomeasurements; and iteratively filtering said first, second, and third local and remote pseudomeasurements to thereby generate an estimated rotation which results in the best agreement between said local and remote pseudomeasurements.