Geometric invariants which completely characterize the size and shape of three dimensional configurations of scattering centers on moving targets can be extracted from signals from ranging sensors such as radar. These invariants can potentially be used to fingerprint and track specific moving targets even when information about changes in the targets orientation between observations is unreliable and when no prior model exists for the target. This technology also creates new possibilities for more robust target recognition.
Mark A. Stuff,
"Three-dimensional invariants of moving targets", Proc. SPIE 4053, Algorithms for Synthetic Aperture Radar Imagery VII, (24 August 2000); doi: 10.1117/12.396363; https://doi.org/10.1117/12.396363