I am dubious of Chris Scott's assertion that the W/V calculations in a pair of uncorrected Inertial systems would diverge. Although the absolute positions diverge, they do so only because they have integrated tiny differences in acceleration vectors. Thus if one inertial platform believes I am heading 342 degrees at 423 knots, and the other thinks I am heading 343 degrees at 422 knots, then after an hour or so the two positions will differ by a significant amount - but the instant wind vector calculation should still be within a degree and a knot between the two boxes.