| The location of a stationary emitter can be determined from 2 or more moving collectors by comparing the times and frequencies from the same signal as received at the different collectors. These Time-Difference-Of-Arrival (TDOA) and Frequency-Difference-Of-Arrival (FDOA) techniques have long been used for target geolocation.
This particular client had an additional complication however in that an unknown number of the emitters were moving. Ignoring the motion of these targets leads to serious errors in TDOA/FDOA geolocation. A workstation operator will not know a priori which emitters are moving and cannot simply choose to avoid moving emitters. He or she will instead end up with an inaccurate geolocation due to ignored emitter motion and be completely unaware of this fact.
S&ST was called upon to team with the client in producing a high-precision method to determine the State Vector (location AND velocity) of the moving emitter. This allows for first determining if the emitter is moving or stationary and then determination of its position and/or velocity using a preferred technique. The simulation and development was successfully performed by S&ST in both MATLAB and then in FORTRAN (to be used with the existing software in the Geolocation workstation). Some of the specific items addressed included: |
