FOREWORD 



Increased knowledge of tropospheric and ionospheric effects on electromagnetic propagation, 

 gained through artificial satellite experiments and related studies, foreshadows an increased 

 accuracy requirement in the geodetic parameters involved in computing charts and tables for 

 electromagnetic navigational and positioning systems. This report examines some of the mathe- 

 matical models involved in these computations, verifying their adequacy for past requirements 

 and introducing modifications to improve range and accuracy capabilities. 



0. D. WATERS, Jr. ^"^ 



Rear Admiral, U. S. Navy 



Commander 



U. S. Naval Oceanographic Office. 



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