Method and device for determining the distance between an airborne receiver and a stationary ground transmitter

Patent metadata

Field	Value
Publication number	US-11415688-B2
Application number	US-201615764167-A
Country	US
Kind code	B2
Filing date	Sep 27, 2016
Priority date	Oct 2, 2015
Publication date	Aug 16, 2022
Grant date	Aug 16, 2022

Abstract

A method and device for determining the distance between an airborne receiver and a stationary ground transmitter are disclosed. A digital terrain model is implemented to determine a range of distance values containing the transmitter. A receiver distance is found and, with the range of values, a plurality of theoretical distances is calculated, to each of which a corresponding azimuth angle and elevation angle are associated. The thus calculated azimuth and elevation angles are compared to the measured azimuth and elevation angles of the line of sight under which the receiver observes the transmitter.

First claim

The invention claimed is:

1. A method performed by a missile launch detector mounted on an aircraft for continuous determination of a distance between a mobile airborne infra-red receiver on a known trajectory and a stationary ground transmitter producing infra-red emissions from a missile launch, said transmitter being observed by said airborne infra-red receiver following a line of sight of variable direction upon movement of said airborne infra-red receiver, the method comprising:
implementing a digital terrain model which is representative of terrain on which said stationary transmitter is found and which indicates a maximum elevation and a minimum elevation of this terrain, wherein implementing the digital terrain model includes determining a maximum distance value and a minimum distance value, for each of a plurality of successive positions of said airborne infra-red receiver for the entirety of its trajectory, and defining a range of distance values in which the real value of the distance between said airborne infra-red receiver and said transmitter in the corresponding position of said airborne infra-red receiver is found;
at each of said successive positions of said airborne infra-red receiver, measuring the value of the azimuth angle and the value of the elevation angle of the corresponding direction of said line of sight;
for each of a plurality of points of the part of said digital terrain model included in each of said ranges of distance values obtained in said implementing a digital terrain model, calculating a theoretical distance between said point and said airborne infra-red receiver, as well as the values of a theoretical azimuth angle and a theoretical elevation angle of the direction of said theoretical distance;
comparing the results of the measured values of the azimuth angle and the elevation angle to the results of the theoretical values of the azimuth angle and the theoretical elevation angle; and
determining that a progression of the real distance between the airborne infra-red receiver and the transmitter, while said airborne infra-red receiver moves along its trajectory, is represented by a progression of the theoretical distance calculated in said calculating, for which the results of the values of the theoretical azimuth angle and the theoretical elevation angle are respectively the closest of the results of the measured azimuth angle and the elevation angle of said line of sight.

2. A missile launch detector for an aircraft, the missile launch detector comprising:
an infra-red detector configured to detect a land-based infra-red emission from a missile launch, and computer hardware programmed to, at least:
indicate the direction of a line of sight under which said infra-red detector observes said infra-red emission, calculate values of an azimuth angle and an elevation angle for the direction of said line of sight;
implement a digital terrain model which is representative of terrain on which said land-based infra-red emission is found and which indicates a maximum height and a minimum height of said terrain;
calculate a minimum distance value and a maximum distance value between which the real value of the distance between said infra-red detector and said land-based infra-red emission is found;
calculate a plurality of theoretical intermediate distances included between said minimum distance value and said maximum distance value;
calculate for each of said theoretical intermediate distances, the azimuth angle and the elevation angle of the corresponding direction;
compare the calculated values of the azimuth angle and the elevation angle of each of said theoretical intermediate distances with the measured values of the azimuth angle and the elevation angle of the direction of said line of sight;
attribute, at a plurality of time instances, the value of the theoretical intermediate distance of which the calculated values of the azimuth angle and the elevation angle are the closest of the measured values of the azimuth angle and the elevation angle of the direction of said line of sight to the distance between the infra-red detector and said land-based infra-red emission; and
assimilate the progression over time of the distance between the infra-red detector and said land-based infra-red emission into a progression over time of theoretical intermediate distance for which the results of the calculated values of the theoretical azimuth angle and the theoretical elevation angle are respectively the closest of the results of the measured values of the azimuth angle and the elevation angle of said line of sight.

3. An aircraft equipped with a missile launch detector, the missile launch detector comprising:
an infra-red detector configured to detect a land-based infra-red emission from a missile launch, and computer hardware programmed to, at least:
indicate the direction of a line of sight under which said infra-red detector observes said infra-red emission, calculate values of an azimuth angle and an elevation angle for the direction of said line of sight;
implement a digital terrain model which is representative of terrain on which said land-based infra-red emission is found and which indicates a maximum height and a minimum height of said terrain;
calculate a minimum distance value and a maximum distance value between which the real value of the distance between said infra-red detector and said land-based infra-red emission is found;
calculate a plurality of theoretical intermediate distances included between said minimum distance value and said maximum distance value;
calculate for each of said theoretical intermediate distances, the azimuth angle and the elevation angle of the corresponding direction;
compare the calculated values of the azimuth angle and the elevation angle of each of said theoretical intermediate distances with the measured values of the azimuth angle and the elevation angle of the direction of said line of sight;
attribute, at a plurality of time instances, the value of the theoretical intermediate distance of which the calculated values of the azimuth angle and the elevation angle are the closest of the measured values of the azimuth angle and the elevation angle of the direction of said line of sight to the distance between the infra-red detector and said land-based infra-red emission; and
assimilate the progression over time of the distance between the infra-red detector and said land-based infra-red emission into a progression over time of theoretical intermediate distance for which the results of the calculated values of the theoretical azimuth angle and the theoretical elevation angle are respectively the closest of the results of the measured values of the azimuth angle and the elevation angle of said line of sight.

Assignees

• Mbda France

Inventors

• Rocher Hélène
• Garrigues Pierre

Classifications

• G01S3/782

  Systems for determining direction or deviation from predetermined direction · CPC title

• G01S5/16

  using electromagnetic waves other than radio waves · CPC title

• G01S7/495

  Counter-measures or counter-counter-measures {using electronic or electro-optical means} · CPC title

• F41G7/224 Primary

  Deceiving or protecting means (jamming or anti-jamming of radio-wave systems in general G01S7/36, G01S7/38; defense installations in general F41H11/02; chaff dispensers F42B12/70) · CPC title

• G01S11/12 Primary

  using electromagnetic waves other than radio waves · CPC title