Tensor Invariant Processing for Munitions/Clutter Classification
Abstract
The intent of this research project is to explore alternatives to conventional dipole inversion for extracting target features from multi-axis EMI sensor array data. Conventional dipole inversion searches for the target parameter values (location and polarizabilities) which minimize the difference between measured signals and those calculated using the dipole response model. Here, we consider an alternative approach that seeks to determine the parameter values which minimize an objective function based on the dispersion in estimates of the target s polarizability using different combinations of transmitters and receivers. The alternative inversion approach exploits rotationally invariant properties of the polarizability tensor. Focusing the processing on the primary invariant (trace of the polarizability tensor) allows us to significantly limit the search space that is required to invert EMI data. Conventional dipole inversion requires that we search over target (x, y, z) location, target ( , , ) orientation and ( 1, 2, 3) principal axis polarizabilities to minimize the difference between the measured response and response predicted by the dipole model fit. With tensor invariant processing we only need to search on (x, y, z) to find the target location which minimizes the dispersion in calculated values for the rotationally invariant trace. The principal axis polarizabilities can then be calculated directly. This report documents results on the convergence properties of a downhill simplex based algorithm for determining a target s location (and polarizabilities) using this approach. Specifically we examined convergence of the algorithm for data collected with the 2x2 TEM array at the former Camp Beale in 2011 and found no impact due to signal-to-noise ratio (SNR) and background leveling effects.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 2013
- Accession Number
- ADA606677
Entities
People
- Thomas Bell