Method of locating a radiating target

• US 3,922,533 A
• Filed: 01/28/1975
• Issued: 11/25/1975
• Est. Priority Date: 03/22/1974
• Status: Expired due to Term

• Current Assignee: Douglas E. Royal
• Original Assignee: Douglas E. Royal
• Inventors: Royal, Douglas E.
• Primary Examiner(s): Gruber, Felix D.
• Application Number:
  US05/544,726
• Time in Patent Office: 301 Days
• Field of Search: 235/150.25,150.26,150.27 444/1 343/112R,112C,113R,5DP
• US Class Current: 342/442
• CPC Class Codes: G01S 1/02 using radio waves G01S19/00 takes precedence

Abstract

A method of locating a radiating target which eliminates the principal source of error of conventional systems. Thus, the target location can be determined on the basis of relative bearing angles which are quite erroneous. A platform such as an airplane is moved along an arbitrary flight path while relative bearing angles to the target are determined by means of the radiated wave. For different positions of the platform both the heading of the platform with respect to a known point, and the location of the platform with respect to a known landmark are determined. Then a first pair of positions of the platform is identified in an automatic manner, each having the same first relative bearing angle. Then the same procedure is repeated for identifying a second pair of positions, each having the same second relative bearing angle to the target. For the first two positions of the platform a first circle may be calculated from the distance between the first two positions and the included angle from the first two positions to the target. Similarly a second circle may be calculated passing through the third and fourth positions. The target is then located at the coordinates of the intersection of the two circles. Various modifications of this method are also disclosed.

Claims

1. The method of locating a target radiating a wave, comprising a moving platform carrying equipment for moving the platform, obtaining bearing angle, heading and location data, and additional equipment for operating upon the data including identifying identical bearing angles, the method comprising the steps of:

a. moving the platform along an arbitrary flight path in the vicinity of the target;

b. recording by means of the radiated wave for different positions of the platform along the flight path relative bearing angles to the target which may contain large errors;

c. recording for different positions of the platform the heating thereof with respect to a known point;

d. recording for different positions of the platform the location thereof with respect to a known landmark;

e. identifying a first and a second position of the platform having a first and a second relative bearing angle with respect to the target;

f. calculating, based on the bearing, heading and location data of the first and second positions, a portion of a first circle passing through the first and second positions of the platform and the target, the first circle being calculated from the distance between the first and second positions and the included angle from the first and second positions to the target;

g. identifying a third and a fourth position of the platform having a third and a fourth relative bearing angle with respect to the target, the second relative bearing angle being determinable from the first relative bearing angle and the fourth relative bearing angle being determinable from the third relative bearing angle; and

h. calculating, based on the bearing, heading and location data of the third and fourth positions a portion of a second circle passing through the third and fourth positions of the platform and the target, the second circle being calculated by the distance between the third and fourth positions and the included angle from the third and fourth positions to the target, whereby the target location is determined by the intersection of the two circle portions.

2. The method defined in claim 1 wherein the first relative bearing angle is equal to the second relative bearing angle.

3. The method defined in claim 1 wherein the third relative bEaring angle is equal to the fourth relative bearing angle.

4. The method defined in claim 1 wherein the third position of the platform coincides with the second position, whereby the third relative bearing angle equals the second relative bearing angle and whereby the second circle is defined by the second and fourth positions of the platform and the target.

5. The method defined in claim 1 wherein the known landmarks are physically located in the vicinity of the target.

6. The method defined in claim 5 wherein an image of the vicinity of the target and of the known landmark is prepared;

and the image of the landmark is then used to determine the location of the platform.

7. The method defined in claim 1 wherein a fifth position of the target is determined having the same relative bearing angle as one of said first and second or one of said third and fourth relative bearing angles, whereby a portion of a third circle may be calculated by means of the data relating to said fifth position, the third circle passing through said fifth position, said target and one of the other positions having the same bearing angle as said fifth position, thereby uniquely to determine the position of the target.

8. The method defined in claim 1 which includes the additional steps of:

a. determining a fifth position of the platform having a fifth relative bearing angle to the target, determining a sixth position of the target having the same fifth relative bearing angle to the target, and calculating a third circle passing through the fifth and sixth position of the platform and the target, the third circle being calculated from the distance between the fifth and sixth positions and the included angle from the fifth and sixth positions to the target, thereby uniquely to determine the location of the target.

9. In the method of locating a target radiating a wave, comprising a platform moved along an arbitrary flight path in the vicinity of the target, the platform carrying equipment for obtaining and recording bearing angle, heading and location data, and additional equipment for operating upon the data including identifying identical bearing angles, the method of automatically performing the steps of:

a. recording by means of the radiated wave for different positions of the platform along the flight path relative bearing angles to the target which may contain large errors;

b. recording for different positions of the platform the heading thereof with respect to a known point;

c. recording for different positions of the platform the location thereof with respect to a known landmark;

d. identifying a first pair of positions of the platform, each having the same first relative bearing angle to the target;

e. identifying at least a second pair of positions of the platform, each having the same second relative bearing angle to the target;

f. calculating, based on the bearing, heading and location data of the first and second positions, a portion of a first circle passing through the first and second positions of the platform and the target, the first circle being calculated from the distance between the first and second positions and the included angle from the first and second positions to the target; and

g. calculating, based on the bearing, heading and location data of the third and fourth positions, a portion of a second circle passing through the third and fourth positions of the platform and the target, the second circle being calculated from the distance between the third and fourth positions and the included angle to the target, whereby the target location is determined by the intersection of the two circle portions.

10. In the method of locating a target radiating a wave, comprising a platform moved along an arbitrary flight path in the vicinity of the target, the platform carrying equipment for obtaining bearing angle, rate of change thereof, heading and location data, and additional equipment for operating upon the data including identifying identical bearing angles, the method of performing the steps of:

a. determining by means of the radiated wave for different positions of the platform along the flight path relative bearing angles to the target which may contain large errors;

b. determining for different positions of the platform the rate of change of the relative bearing angle as a function of distance of the platform from a particular position;

c. determining for different positions of the platform the heading thereof with respect to a known point;

d. determining for different positions of the platform the location thereof with respect to a known landmark;

e. identifying two positions of the platform, each having the same first relative bearing angle to the target;

f. determining the rate of change of the bearing angle as a function of distance from the first and the second position;

g. calculating, based on the bearing, rate of change thereof, heading and location data of the first and second positions, a portion of a circle passing through the first and second positions of the platform and the target, the circle being calculated from the distance between the first and second positions and the included angle from the first and second positions to the target; and

h. calculating the position of the target on the portion of the circle by the intersection of two lengths L1 and L2, the length L1 extending from the first position to the target and the length L2 intersecting the length L1 from the second position to the target, the ratio L2/L1 being determined by the ratio of the rate of change of the bearing angle at the first position to the rate of change of the bearing angle of the second position.

11. The method of locating a target radiating a wave, comprising a moving platform carrying equipment for moving the platform, recording and obtaining bearing angle, determining rate of change of phase angle, heading and location data, and additional equipment for operating upon the data including identifying identical bearing angles, the method comprising the steps of:

a. moving the platform along an arbitrary flight path in the vicinity of the target;

b. recording by means of the radiated wave for different positions of the platform along the flight path relative bearing angles to the target which may contain large errors;

c. determining the rate of change of an interferometric phase angle determined from a first relative bearing angle as a function of distance of the platform from a first associated position and determining the rate of change of an interferometric phase angle derived from the first relative bearing angle as a function of distance from a second position having the same first relative bearing angle;

d. determining for different positions of the platform the heading thereof with respect to a known point;

e. determining for different positions of the platform the location thereof with respect to a known landmark;

i. calculating, based on the bearing, heading and location data of the first and second positions, a portion of a circle passing through the first and second positions of the platform and the target, the first circle being calculated from the distance between the first and second positions and the included angle from the first and second positions and the included angle from the first and second positions to the target; and

j. calculating the position of the target on the portion of the circle by the intersection of two lengths L1 and L2, the length L1 extending from the first position to the target and the length L2 intersecting the length L1 from the second position to the target, and the ratio L2/L1 being determined by the ratio of the rate of change of the interferometric phase angle at the first position to the rate of change of the interferometric phase angle at the second poSition.

12. The method of locating a target radiating a wave, comprising a moving platform carrying equipment for moving the platform, determining location and heading data and antenna radiation patterns, and additional equipment for operating upon the data and correlating antenna patterns, the method of automatically performing the steps of:

a. moving the platform along an arbitrary flight path in the vicinity of the target;

b. generating antenna radiation patterns near a first, a second and a third position along the flight path in response to the radiation of the target, the antenna patterns being a function of direction;

c. determining the location and heading of the platform at the first, second and third position with respect to a known landmark;

d. calculating, based on the antenna radiation pattern and location data of the first and second positions, a portion of a first circle passing through the first and second positions of the platform and the target, the first circle being calculated from the distance between the first and second positions and the included angle from the first and second positions to the target; and

e. calculating based on the antenna radiation pattern and location data of the three positions, a portion of a second circle passing through the third and one of the first and second positions of the platform and target, the second circle being calculated from the distance between the third and one of the first and second positions and the included angle from the third and one of the first and second positions to the target, whereby the target location is defined by the intersection of the two circle portions.

13. The method of locating a target radiating a wave, comprising a moving platform carrying equipment for moving the platform, obtaining and recording bearing angle and for mapping landmarks, and additional equipment for operating upon the data, the method comprising the steps of:

a. moving the platform along an arbitrary flight path in the vicinity of the target;

b. recording by means of the radiated wave for different positions of the platform along the flight path relative bearing angles to the target which may contain large errors;

c. mapping a first plurality of landmarks at a first position of the platform and a second plurality of landmarks at a second position of the platform and a third plurality of landmarks at a third position of the platform, said second and third positions having the same relative bearing angle as the first position. d. calculating, based on the bearing and landmark mapping data, a portion of a first circle passing through the first and second positions of the platform and the target, the first circle passing through those landmarks which during the first and second mapping steps have the same angle, said angle corresponding to the angle determined by the first relative bearing; and

e. calculating, based on the bearing and landmark data a portion of a second circle passing through the second and third positions of the platform and the target, the second circle passing through those landmarks which during the second and third mapping steps have the same angle, said angle corresponding to the angle determined by the first relative bearing, whereby the target location is defined by the intersection of the two circle portions.

14. The method of locating a target radiating a wave, comprising two moving platforms, each carrying equipment for obtaining bearing angle, heading and location data, and additional equipment for operating upon the data including identifying identical bearing angles, the method of performing the steps of:

a. recording by means of the radiated wave for different positions of the first platform along the flight path relative bearing angle to the target which may contain large errors;

b. recording for different positions of the first platform the heading thereof with respect to a known point;

c. recording for different Positions of the first platform the location thereof with respect to a known landmark;

d. recording by means of the radiated wave for different positions of the second platform along the flight path relative bearing angles to the target;

e. recording for different positions of the second platform the heading thereof with respect to a known point;

f. recording for different positions of the second platform the location thereof with respect to the known landmark;

g. identifying a first position of the first platform and a second position of the second platform different from the first position, each having a first and a second relative bearing angle different from each other;

h. identifying a third position of the first platform and a fourth position of the second platform, the third position having the same first relative bearing angle and the fourth position having the same second relative bearing angle;

i. calculating, based on the bearing, heading and location data, a portion of a first circle passing through the first and third positions of the two platforms and the target, the first circle being calculated from the distance between the first and third positions of the two platforms and the included angle from the first and third positions of the two platforms to the target; and

j. calculating a portion of a second circle passing through the second and fourth positions of the two platforms and the target, the second circle being calculated from the distance between the second and fourth positions of the platforms and the included angle from the second and fourth positions of the platforms to the target, whereby the target location is defined by the intersection of the two circle portions.