320 



REFRACTION AND REFRACTIVE INDEX MODELS 



practically possible to zero, and both models show comparable rms errors 

 for do = 0, one concludes that there is no clear advantage to the bi- 

 exponential model for this application. This conclusion is furthered by 

 the fact that charts of Hd, Hy,, Do, and Wo are not available, while to use 

 the single exponential model one need only to refer to existing regional 

 or worldwide maps [10, 12]. 



4.0 



(T 



or 

 o 

 (r 

 (r 



UJ 

 CD 



Q 



LxJ 

 CD 



^ 0.3 





 0.4 



= 



EXP. REF 



I -EXP. 



9„ = ?0mr 



9n-- 50 mr 



EXP REF 



BI-EXP 



n 



0n=IOOmr 



-EXP REF 



-BI-EXP 



0,5 



0,4 



0.3 



0.2 



0.1 





 0.20 



0.16 



0.12 



0.08 



0.04 



cr 

 o 

 cr 

 cr 



UJ 



LU 

 CD 



CD 



cr 



3 10 15 70 3 10 15 70 



HEIGHT IN KILOMETERS 



Figure 8.9. Rool-mean-square errors of predicting bending for both the bi-exponential 



refractive index model and the C.R.P.L. (single) exponential atmosphere. 



Height is used here to indicate the actual thickness of atmosphere traversed by the radio ray 



