62 



HANDBOOK OF MAGNETIC COMPASS 



at various positions on the sphere brackets, and with different mag- 

 netic moment compasses. These quadrantal corrections apply whether 

 the spheres are used as D^ E^ or combination Z> and E correctors. 

 Quadrantal correction from spheres is due partially to earth's -field 

 induction and partially to compass needle induction. Since compass 

 needle induction does not change with magnetic latitude, and earth's 

 field induction does, the sphere correction is not constant for all mag- 

 netic latitudes. A reduction in the percentage of needle induction in 

 the spheres to the earth's field induction in the spheres will improve the 

 constancy of sphere correction over all magnetic latitudes. Such a 

 reduction in the percentage of needle induction may be obtained by : 



( 1 ) Utilizing a low magnetic moment compass. See article 102. 



(2) Utilizing special spheroidal-shaped correctors, placed with 

 their major axes perpendicular to their axis of position. 



(3) Using larger spheres farther away from the compass. 



Twersf ARe APPKoxiMATe- coat. 



etr/<M/s. VirFeReNT c^ompass 



VffOif- AUKAYS VIILL ALTB-K 



<J /z /« ^4 



Le-nsth of FLiMoeRs 3/»ie - Jnchc"? 



QuAbRAhimL EKKor from 

 ^TD. NiAvr FLiuoeRs "Bar 



FiGXJRE 32. 



93. Quadrantal error from Flinders bar. — Figure 32 presents the 

 approximate quadrantal error introduced by the presence of Stand- 

 ard Navy Flinders bar. Since the Flinders bar is generally placed 

 in the forward or aft position, it acts as a small minus D corrector, 

 as well as a corrector for vertical induced effects. This means that 

 upon inserting Flinders bar in such a position, the regular spheres 

 should be moved closer to correct for the increased plus D error, or 

 vice versa, if Flinders bar is removed. This D error in the Flinders 



