Multilateration auto-calibration and position error correction

DETAILED DESCRIPTION The Multilateration Auto-Calibration & Position Error Correction System of the present invention is a truly passive method of error detection and correction.
The system utilizes the Side Lobe Suppression (SLS) pulse from an SSR as a reference signal from a known position to determine error corrections.
The SLS pulse possesses a high transmission rate, radiates from a source having a known position, and is omni-directional.
Thus, the SLS pulse makes an ideal reference signal for error correction calculations.
The DTOAs for the SLS pulse are a known constant.
Therefore, the received DTOAs from the SLS pulse are compared to the calculated DTOAs in the same fashion as the reference transponder method and the corrections for each receiver calculated based on the difference in the known DTOA and the received DTOA.
Any subsequent receptions of a 1090 MHz signal from a transponder are corrected with an individual correction time for each receiver thereby calibrating the system of receivers used for multilateration.
These corrections are made prior to multilateration calculations.
The method of calibration has the capability to correct receivers that are not in line of sight with the SSR transmitter.
When a correction is obtained for a set of receivers, the receivers can perform multilateration on any given transponder with great accuracy.
When the calibrated set of receivers computes the location of a transponder, the time of transmission may then also be computed.
Time of transmission from a transponder plus the propagation times for individual receivers may then be compared to the actual TOA at the receiver.
The time difference in calculated and observed TOAs is the error correction for that individual receiver.
The error correction method of the present invention requires only one set of receivers to be calibrated directly by the SSR SLS pulse.
As long as there are transponders broadcasting where the transmitted signal is received by one calibrated set of receivers for multilateration, error detection and system calibration can be performed on any other receiver detecting the same transponder signal