Multilateration auto-calibration and position error correction
First Claim
1. A method for calibrating a multilateration system, comprising the steps of:
- receiving, at a plurality of first radio receivers having known position values, a first radio signal from a first transmitter having a known position value;
measuring a first time value when the first radio signal is received at one of the plurality of first radio receivers;
measuring first time difference values between when the first radio signal is received at the one of the plurality of first radio receivers and when the first radio signal is received at others of the plurality of first radio receivers;
calculating a first theoretical time difference values for each of the others of the plurality of first radio receivers based upon the known position value of the first transmitter and the known position values of the first radio receivers; and
generating first error correction values, for each of the others of the plurality of first radio receivers, proportional to the difference between the first time difference values and the first theoretical time difference values.
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Accused Products
Abstract
The accuracy of multilateration systems can be greatly improved by using a correction method based on the SLS (Sideband Lobe Suppression) signal produced by a Secondary Surveillance Radar (SSR). Multilateration is a cooperative surveillance technique for aircraft equipped with Air Traffic Control Radar Beacon System (ATCRBS), Mode S, or Automatic Dependent Surveillance Broadcast (ADS-B) transponders. When one of these transponders aboard a vehicle is interrogated, it responds by broadcasting a message based on what the interrogation requests. These reply messages may be multilaterated to determine the source position of the transmission. Multilateration is a Time Difference of Arrival (TDOA) technique similar to triangulation. Multilateration can be performed to locate the transmission source of any SSR signal. Error detection and correction may be performed on the system by conducting a comparison of a known TDOA for the receiver/transmitter geometry, to the measured TDOA from a Side Lobe Suppression (SLS) pulse emanating from a primary radar.
101 Citations
14 Claims
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1. A method for calibrating a multilateration system, comprising the steps of:
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receiving, at a plurality of first radio receivers having known position values, a first radio signal from a first transmitter having a known position value; measuring a first time value when the first radio signal is received at one of the plurality of first radio receivers; measuring first time difference values between when the first radio signal is received at the one of the plurality of first radio receivers and when the first radio signal is received at others of the plurality of first radio receivers; calculating a first theoretical time difference values for each of the others of the plurality of first radio receivers based upon the known position value of the first transmitter and the known position values of the first radio receivers; and generating first error correction values, for each of the others of the plurality of first radio receivers, proportional to the difference between the first time difference values and the first theoretical time difference values. - View Dependent Claims (2, 3, 4, 5)
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6. A method for accurately determining aircraft position, comprising the steps of:
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receiving, at a plurality of first radio receivers having known position values, a sideband lobe suppression pulse from a radar transmitter having a known position value; measuring a first time value when the sideband lobe suppression pulse is received at one of the plurality of first radio receivers; measuring first time difference values between when the sideband lobe suppression pulse is received at the one of the plurality of first radio receivers and others of the plurality of first radio receivers; calculating first theoretical time difference values for each of the others of the plurality of first radio receivers based upon the known position value of the radar transmitter and the known position values of the plurality of first radio receivers; generating first error correction values, for each of the others of the plurality of first radio receivers, proportional to the difference between the measured first time difference values and the first theoretical time difference values; receiving, at the plurality of first radio receivers, an aircraft transponder signal from an aircraft transponder responding to a radar signal from the radar transmitter; measuring a second time value when the aircraft transponder signal is received at one of the plurality of first radio receivers; measuring second time difference values between when the aircraft transponder signal is received at the one of the plurality of first radio receivers and others of the plurality of first radio receivers; adding corresponding error correction values for each of the plurality of first radio receivers to each of the second difference values produce corrected second time difference values; and generating a multilaterated position value of the aircraft from the corrected second time difference values. - View Dependent Claims (7, 8, 9)
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10. A multilateration system, comprising:
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a plurality of radio receivers of known position, for receiving a radio signal from a transmitter of known position; means for measuring time values when the radio signal is received at each of the plurality of radio receivers; means for generating a plurality of time difference values between measured time values for the plurality of radio receivers; means for calculating theoretical time difference values between measured time values for the plurality of radio receivers based upon the known position value of the transmitter and the known position values of the radio receivers; means for generating error correction values, for each of the plurality of time difference values, proportional to the difference between the measured time difference values and the theoretical time difference values; and means for adding the error correction values to subsequently recieved time difference values generated in response to a received radio signal from a transmitter of initial unknown position, to generate corrected time difference values; and means for generating a multilaterated position value of the transmitter of initial unknown position from the corrected measured time difference values. - View Dependent Claims (11, 12, 13)
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14. A method of accurately multilaterating position of a transmitter of unknown position, comprising the steps of:
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multilaterating a position of a first transmitter of known position to generate a first multilaterated position value; comparing the first multilaterated position value with the known position of the first transmitter to generate a difference value; multilaterating a position of a second transmitter of unknown position to generate a second multilaterated position value; and correcting the second multilaterated position value by applying the correction value to the second multilaterated position value.
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Specification