1. A method of estimating position and orientation of an article, comprising: reading the orientation of the article from at least three gyroscopes mounted on the article; reading the acceleration of the article from three accelerometers mounted on the article; at time T estimating a position vector velocity vector V, and orientation matrix O of an article, between T and an initial time T 0 where: an initial position vector=P 0 , an initial velocity vector=V 0 , an initial orientation matrix=O 0 , an initial rotational velocity, relative to the article, vector=R 0 , and an initial acceleration, relative to the article, vector=A 0 ; and re-calculating the position vector P, velocity vector V, and orientation matrix O at a subsequent time T 1 using new information from the accelerometers and gyroscopes where: new acceleration relative to the object vector=A 1 , new rotational velocity relative to the object vector=R 1 ,and the re-calculation is carried out by, linearly interpolating from R 0 to R 1 to discover the local rotational velocity at any time between T 0 and T 1 , and by linearly interpolating from A 0 to A 1 to discover the local acceleration.