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