Methods and apparatus for providing target altitude estimation in a two dimensional radar system

• US 7,417,583 B2
• Filed: 10/30/2006
• Issued: 08/26/2008
• Est. Priority Date: 10/30/2006
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Wood, Thomas E., Heuer, Gregory D., Ager, Robert S., Fleury, Richard B.
• Primary Examiner(s): Tarcza; Thomas H.
• Assistant Examiner(s): GALT, CASSI J
• Application Number:
  US11/554,064
• Publication Number:
  US 20080169967A1
• Time in Patent Office: 666 Days
• Field of Search: 342/41, 342120-123, 342/140
• US Class Current: 342/123
• CPC Class Codes: G01S 13/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S13/46
• CPC Class Codes: G01S 13/723 by using numerical data
• CPC Class Codes: G01S 13/937 of marine craft

Abstract

Method and apparatus to track a contact using a sensor in a two-dimensional radar system, determine a closest point of approach (CPA) for the contact, determine a time to closest point of approach (TCPA) for the contact, and estimate an altitude for the contact from the closest point of approach (CPA) and a cross line of sight distance during the time to closest point of approach (TCPA).

Claims

1. A method, comprising:

tracking a contact using a sensor in a two-dimensional radar system;

determining a closest point of approach (CPA) for the contact;

determining a time to closest point of approach (TCPA) for the contact;

estimating an altitude for the contact from the closest point of approach (CPA) and a cross line of sight distance during the time to closest point of approach (TCPA).

2. The method according to claim 1, further including determining whether the contact is airborne.

3. The method according to claim 1, wherein the estimated contact altitude equals the CPA when the contact is following a constant velocity that leads directly over the radar system sensor.

4. The method according to claim 1, further including using the Pythagorean Theorem to estimate the contact altitude.

5. The method according to claim 1, further including using a negative TCPA as a criterion to determine when an altitude should be estimated for the contact.

6. The method according to claim 1, further including making a series of checks prior to estimating the contact altitude.

7. The method according to claim 6, wherein the checks include one or more of determining whether the contact is a closing contact, determining whether the TCPA is less than a selected value, determining whether the CPA is less than a selected value, and examining a ratio of CPA to range for the contact.

8. The method according to claim 1, further including estimating the contact altitude from a contact range (R) and a rate of change in azimuth (A′

).

9. The method according to claim 1, further including estimating the contact altitude by using a cross line of sight vector for the contact.

10. A system, comprising:

a two-dimensional radar system having a sensor to detect contacts; and

a processing module to track a contact using a sensor in a two-dimensional radar system, determine a closest point of approach (CPA) for the contact, determine a time to closest point of approach (TCPA) for the contact, and estimate an altitude for the contact from the closest point of approach (CPA) and a cross line of sight distance during the time to closest point of approach (TCPA).

11. The system according to claim 10, wherein the processing module determines whether the contact is airborne.

12. The system according to claim 10, wherein the estimated contact altitude equals the CPA when the contact is directly over the radar system sensor.

13. The system according to claim 10, wherein the processing module makes a series of checks prior to estimating the contact altitude.

14. The system according to claim 10, wherein the system includes a ship.

15. An article comprising:

a storage medium having stored thereon instructions that when executed by a machine result in the following;

tracking a contact using a sensor in a two-dimensional radar system;

determining a closest point of approach (CPA) for the contact;

determining a time to closest point of approach (TCPA) for the contact;

estimating an altitude for the contact from the closest point of approach (CPA) and a cross line of sight distance during the time to closest point of approach (TCPA).

16. The article according to claim 15, further including instructions for determining whether the contact is airborne.

17. The article according to claim 15, wherein the estimated contact altitude equals the CPA when the contact is directly over the radar system sensor.

18. The article according to claim 15, further including instructions for using a negative TCPA as a criterion to determine when an altitude should be estimated for the contact.

19. The article according to claim 15, further including instructions for making a series of checks prior to estimating the contact altitude, wherein the checks include one or more of determining whether the contact is a closing contact, determining whether the TCPA is less than a selected value, determining whether the CPA is less than a selected value, and examining a ratio of CPA to range for the contact.

20. The article according to claim 15, further including instructions for estimating the contact altitude from a contact range (R) and a rate of change in azimuth (A′

) and/or using a cross line of sight vector for the contact.