Self-calibrating shooter estimation
View Patent ↗Shockwave-only solutions that estimate shooter position and shot trajectory are extremely sensitive to the quality and precision of the shock time-of-arrival (TOA) measurements as well as the accuracy to which relative sensor positions in space are known. Over the life of a long-deployed system, the sensor positions can shift and the performance of some sensors may degrade for various reasons. Such changes can degrade the performance of deployed shooter estimation systems. Disclosed are systems and methods that can be used to calibrate sensor positions based on shock and muzzle measurements processed from a series of shots fired from a known location and in a known direction, as well as an approach for dynamically adapting shock-only shooter estimation algorithms to compensate for sensor degradation and/or loss.
1. A method for calibrating relative sensor positions of sensors in a shooter detection system, comprising the steps of:
determining approximate relative location information of the sensors;
firing at least two shots having different known shooter positions and known bullet trajectories;
determining a time difference between a muzzle-blast arrival time and a shockwave arrival time for each of the sensors and for each shot; and
determining as calibrated relative sensor positions those relative sensor positions that produce a minimum residual of the time differences for the at least two shots.
2. The method of claim 1 , wherein the calibrated relative sensor positions are determined by performing a least-squares search.
3. The method of claim 2 , wherein the least-squares search is initialized from a previous known location of the sensors.
4. The method of claim 2 , wherein the least-squares search is initialized from an approximately measured location of the sensors.
5. The method of claim 1 , further comprising the steps of selecting one of the sensors as a reference sensor and computing relative muzzle-blast arrival times and a shockwave arrival times for each sensor relative to the reference sensor.
6. The method of claim 1 , wherein the sensor is an acoustic sensor.
7. The method of claim 6 , wherein the acoustic sensor is a microphone.
8. The method of claim 1 , wherein determining approximate relative location information includes defining an initial population of relative sensor locations, and wherein determining the calibrated relative sensor positions includes applying a genetic algorithm to select from a surviving population the relative sensor locations that produce a minimum residual of the time differences for the at least two shots.