INTRODUCTION 



This handbook of magnetic compass correction, for both normal 

 and degaussed conditions, has been prepared in order to present all 

 pertinent information regarding the practical procedures of adjust- 

 ment and compensation in one text. As such, it deals with the basic 

 principles of compass deviations and their correction, and not with 

 the details of particular compass equipment. However, since no 

 standard texts have been prepared on degaussing and its effects on 

 the compass, this text not only includes the principles of degaussing 

 compensations, but also the details of compass compensating coil equip- 

 ments and their electrical characteristics. 



Although this text is presented as a systematic treatise on compass 

 adjustment and compensation, ship's personnel who are inexperienced 

 with compass correction will find sufficient information in chapters 

 I and X to eliminate compass errors satisfactorily without intensive 

 study of the entire text. Reference should also be made to figure 19 

 for condensed information regarding the various compass errors and 

 their correction. 



In this handbook *the term compass adjustment refers to any change 

 of permanent magnet or soft iron correctors whereby normal compass 

 errors are reduced. The term compass coriipensation refers to any 

 change in the currents supplied to the compass compensating coils 

 whereby the errors due to degaussing are reduced. These terms differ 

 from those used in previous compass publications but are in accord- 

 ance with recently approved Navy nomenclature established so as to 

 distinguish between the two correction procedures. 



This text is the outgrowth of lecture notes prepared by the authors 

 while presenting courses of instruction in adjustment and compensa- 

 tion at the Magnetic Compass Demonstration Station, Naval Operat- 

 ing Base, Norfolk, Va. These courses were designed primarily for the 

 Specialist Officer Training Program, and were also utilized by various 

 other training activities in and around" Norfolk. A basic, simplified 

 check-off list was used as the nucleus of these courses, and the lecture 

 material was so designed as to amplify this chech-off list. In view of 

 the obvious need for a practical handbook for Navy personnel, both 

 at shore stations and at sea, it was decided to expand the lecture mate- 

 rial into such a text, based on personal experience with compass adjust- 

 ment, compensation, and compass coil design. 



