86 



THE DEVELOPMENT OF WEAPONS SYSTEM REQUIREMENTS 



; Target 

 Positions for Eacii 

 Look" 



Fig. 2-22 Positk 



CIC Location 



Data Used in Computing Esti 

 Velocity. 



lates of Target Heading and 



Assume that the specified 800-fps target is initially detected at point 1. 

 Since the assumed AEW radar scanning time is 6 seconds, the next look at 

 the target will occur when it reaches position 2. It will be at position 3 on 

 the third look, and so on. At the end of seven looks, the target will be at 

 position 7. The position measurement on each look is characterized by an 

 assumed radial error with a standard deviation of or. This error may be 

 broken into components parallel and normal to the target path, where the 

 standard deviation of each component is^ 



ap = ot/VS n.mi. 

 o"7v = ot/V2 n.mi. 



(2-9) 

 (2-10) 



If the errors of each position measurement are assumed to be independ- 

 ent, the relative errors between any two measurements have the standard 

 deviations 



(TPIP2 — 



v(ty-(iy= 



ar n.mi. (2-11) 



(yN\N2 = or n.mi. (2-12) 



A very simple procedure for determining the target velocity and heading 

 can be based on the extreme position measurements. The estimated 



^Breaking the errors into equal components ignores the influence of the fact that the range 

 and azimuth errors for a given target measurement are markedly different (Equations 2-7 and 

 2-8). If this factor is considered, the mathematical complexity of the problem is greatly 

 increased; the final answer expressing the probable position errors for any randomly chosen 

 target position relative to the CIC is not changed substantially. 



