For preliminary prediction of track accuracy in exoatmospheric applications, a common approach is to apply simple constant-velocity solutions separately in the range direction and two perpendicular crossrange directions. In typical radar applications, however, the range measurement errors are much smaller than the crossrange errors, and this approach neglects the important coupling effect by which the crossrange tracking accuracy, in the plane of motion of the line of sight, may be greatly improved due to the highly accurate range measurements. This paper demonstrates the extent of this effect by developing analytic solutions for the applicable Cramer-Rao bounds in the continuous- measurement case, which are then verified by numerical propagation of covariance matrices for the more realistic discrete-measurement case. A set of simple approximate expressions are presented, which are useful for prediction of tracking performance.
Robert J. Fitzgerald,
"Range-angle coupling in target tracking", Proc. SPIE 3809, Signal and Data Processing of Small Targets 1999, (4 October 1999); doi: 10.1117/12.364026; https://doi.org/10.1117/12.364026