88 THE DEVELOPMENT OF WEAPONS SYSTEM REQUIREMENTS 



There are several means for improving the tracking accuracy. Each of 

 these involves a trade-off between improved accuracy and greater informa- 

 tion-handling complexity. For instance, in the simple case we have just 

 been discussing, when only the extreme position measurements are used 

 all the information associated with interior measurements is lost. If all 

 the position measurements were used to determine the velocity and heading 

 estimates, the errors would be substantially smaller. Thus, the error 

 estimates in Equations 2-18 and 2-19 are somewhat pessimistic. In some 

 cases, a trade-off between maneuvering and nonmaneuvering target track- 

 ing accuracy also is required. 



The velocity and heading estimates may be used in several ways. First 

 of all, this information is used to compute vectoring guidance for the 

 interceptors. The collision vectoring equation (Equation 2-4) illustrates a 

 typical application. Part of the vectoring problem involves prediction of 

 the future positions of the targets and interceptors. Prediction for a single 

 scan is also used to update the position information. An example of such a 

 prediction process is shown in Fig. 2-23. The AEW/CIC system indicates 

 target position as point A. The velocity and heading estimates are used to 

 generate a track AA^ On the next scan, target position is indicated as 

 point B. The position data are corrected to this point and a new continuous 

 track BB^ is estimated, etc. Thus, at any time between measurements a 



A,6,C,D = Measured Target Positions 



a\b\c\d^ = Estimated Target Positions 

 f^c Seconds After 

 Measurements of 

 A,6,C,D Respectively 



Fig. 2-23 Prediction Process Employing Scan-to-Scan Correction of Position Data. 



position measurement is available which accounts for the change in target 

 position since the last measurement was made. This type of information 

 processing (updating) greatly reduces the time-delay error discussed in 

 Paragraph 2-15. 



