Patent ID: 6819230
Filing Date: 2004-11-16
Classification: G01S

Abstract:
A method of predicting and detecting the crossing of two target tracks in a bearing versus time coordinate frame, comprising the steps of:providing a tracking system that outputs a bearing measurement B every K seconds for each of said two target tracks; determining a bearing rate Bâ€² and a projected intercept B0 with a bearing axis of said bearing versus time coordinate frame using said bearing measurement for each of said two target tracks over a most-recently occurring window of time defined by (JÃ—K) seconds, where J is an integer constant greater than two; and determining a crossing time tc for said two target tracks in accordance with tc=(B0,2âˆ’B0,1)/(Bâ€²1âˆ’Bâ€²2) â€ƒwhere B0,1 is said projected intercept for a first of said two target tracks, B0,2 is said projected intercept for a second of said two target tracks, Bâ€²1 is said bearing rate for said first of said two target tracks, Bâ€²2 is said bearing rate for said second of said two target tracks; predicting that said two target tracks will cross if a first inequality defined as (iÃ—K)&lE;tc&lE;K(i+J) â€ƒis satisfied; and predicting that said two target tracks have crossed if a second inequality defined as K(iâˆ’J)&lE;tc&lE;(iÃ—K) â€ƒis satisfied, where i is a counter that is incremented by one every K seconds.