diode voltage reference element to determine the feasibility of using 

 it to replace the mercury batteries and standard cells presently re- 

 quired. 



b. Design and develop a precise current control system for the 

 VAM incorporating automatic base line indexing and both analog and 

 digital recording of data. 



c. Design and construct a new mounting base and gimbals for 

 the VAM detector. These would improve the reliability of declination 

 measurements by preventing small azimuth reference errors in the 

 VAM due to vibration, shock, roll, and pitch. 



d. Develop a system for automatic magnetometer data recording. 

 This system should be directed towards satisfying computer input 

 requirements and have sufficient flexibility to provide for increased 

 accuracy at a future date. 



e. Develop and procure a portable recording magnetometer 

 suitable for field use. This instrument, used in the survey area, may 

 be useful for evaluating survey flights, particularly in auroral regions 

 where large short-period fluctuations are not infrequent. 



Magnetic data of higher accuracy than currently achieved doubtless 

 will be required throughout the world. Toward this end, it will be 

 necessary to utilize somewhat more sophisticated instrumentation. 

 To obtain more accurate data on the direction of the magnetic field, 

 it will be necessary to employ an accurately stabilized platform as 

 a frame of reference. Additionally, it will be necessary to obtain 

 precise, absolute measurements of the field strength, possibly with 

 a nuclear precession or alkali vapor magnetometer. The accuracy 

 of survey navigation must be improved before any significant increase 

 in survey accuracy can be achieved with new magnetometer equipment. 

 To achieve such longer range objectives, it is recommended that the 

 Hydrographic Office: 



f. Support the development of an improved airborne vector 

 magnetometer of greater precision than existing instruments. One 

 approach to this problem lies in adopting an overall system viewpoint 

 for the magnetic airborne survey. Treated in this way, the survey 

 system can be broken down into six subsystems: (1) Navigation sub- 

 system to provide astronomic position, directional and vertical refer- 

 ences, ground velocity, and time; (2) magnetic vector subsystem to 

 provide direction and intensity of the magnetic field; (3) magnetic 



XIV- 10 



