measurements should be followed closely for possible advantages in 

 simplicity and versatility in operation. Development of means for 

 telemetering information directly to a ship or other central location 

 is desirable. 



O. GRAVITY MEASUREMENTS 



The most pressing requirements for more accurate gravity surveys 

 at sea are: (1) a calibration range off the Atlantic Coast and (2) a small 

 portable land instrument for measuring absolute gravity to an accuracy 

 of ±0.1 milligal or less. 



Marine gravimeters should be improved and miniaturized for 

 more continuous use aboard surface ships as well as submarines. Be- 

 cause of its primary interest in marine gravity surveys, the Hydro- 

 graphic Office should evaluate, or participate in the evaluation of, new 

 marine gravimeters developed or considered for Navy use. Progress 

 on development of a practical airborne gravimeter should be followed 

 closely by this Office for possible future use of such an instrument 

 aboard Project MAGNET or other aircraft. Means should be provided 

 for incorporating gravity measurements in any geophysical data 

 collection system developed by the Hydrographic Office. 



P. GEOMAGNETIC MEASUREMENTS 



To meet requirements for small-scale isomagnetic charts, the 

 instrumentation for airborne geomagnetic surveys can be considered 

 reliable and accurate. Some improvements in reliability, efficiency, 

 and flexibility could be achieved by: (1) development of a low drift 

 voltage standard and a precise current control system for the Vector 

 Airborne Magnetometer, (2) improvement of the mounting for the VAM 

 detector, (3) automation of the recording system, and (4) development 

 of a portable recording magnetometer. 



Also, the Hydrographic Office should support development of im- 

 proved vector and total field magnetometers to meet future require- 

 ments. 



Q. POSITIONING 



More accurate long-range positioning equipment is a continuing 

 requirement. A problem requiring immediate attention is that of 

 determination of correction factors to be applied to positions obtained 

 by existing radio positioning systems operating over different surfaces 

 and under different atmospheric conditions. Automatic incorporation 



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