maintains all the desirable features and eliminates most of the disad- 

 vantages. The size has been reduced so that the meter, rechargeable 

 power supply (batteries), and battery charger and battery eliminator 

 weigh a total of about 15 pounds. The combination of no drift, rapid 

 reading, and facility of transportation makes this a good instrument 

 for world-wide operations. 



d. Other gravimeters (land) 



In addition to the types of gravimeters currently owned by 

 the Hydrographic Office, one other manufactured in the United States, 

 the n World- Wide" meter, is described as being very similar in most 

 respects to the Worden meter. Several foreign- made gravimeters 

 also are currently on the market, but from all reports these are less 

 accurate than the U. S. instruments. 



C. RECOMMENDATIONS 



1. Recommendations for improvement of existing instruments 



a. Although currently available gravimeters meet most survey 

 requirements, submarine meters should be converted for either 

 shipboard or submarine use and miniaturized to permit operation in 

 all sea conditions. The small size also would permit continued use 

 aboard submarines when required. As practicable, ocean gravity 

 meters should be included as standard items aboard all Hydrographic 

 Office survey ships. 



b. A calibration range for use in checking and calibrating all 

 sea gravimeters should be established at sea along the east coast 

 of the United States. The range should consist of several accurately 

 surveyed areas each approximately one degree square, and located 

 at intervals of 5° of latitude. Meanwhile, calibration of all gravity 

 instruments in this Office should be accomplished as soon as practic- 

 able over all or part of the coastal areas presently surveyed in the 

 region extending from Ottawa, Canada to Key West, Florida. This is 

 necessary for accurate comparison of all data obtained with various 

 meters and should be done at regular intervals to insure that any 

 changes of calibration are known. 



c. Navigational instruments should be improved or developed 

 to allow more accurate positioning than can be achieved at present. 



XIII- 6 



