Meter. Recent improvements in the contact mechanism are expected 

 to prolong meter life, and fin and propeller configurations have been 

 redesigned to reduce the threshold value. However, it is recommended 

 that the standard procedures of current measurement, as now used in 

 the field, be followed until improved methods of data analysis are fully- 

 developed, operational, and practical. 



It will not be possible to adopt one instrument exclusively for all 

 current measurements taken by the Hydrographic Office. Occasions 

 will arise where only the unique characteristics of special instruments 

 can adequately provide the required measurements. Therefore, it is 

 recommended that the capability of the Hydrographic Office for meas- 

 uring currents by using diversified principles be maintained and even 

 expanded. However, it is felt that a large percentage of the required 

 current observations can now be accomplished with the Roberts Meter 

 and that future computer -input modifications will yield great savings 

 in data analysis effort. 



Other meters which show promise and may in time approach the 

 versatility of the Roberts Meter are the Ott, Iwamiya, Dunkerque, 

 and Snodgrass meters. The Hydrographic Office has plans for pro- 

 curing two Iwamiya Meters. However, no immediate plans exist for 

 evaluation of the Ott and Dunkerque meters. It is recommended that 

 the Savonius rotor type meter (Snodgrass Meter) be investigated 

 further for its possible incorporation into an ultimate data handling 

 system and that one of these meters be purchased and evaluated by 

 this Office. 



In view of the high cost and nonrecoverability of neutral buoyancy 

 acoustic sources, it is recommended that the Hydrographic Office not 

 participate at this time in the development of this technique. 



Several government agencies are pursuing the development of 

 current meters, either through contracts or by use of their own facil- 

 ities. Although these efforts are directed toward special-purpose 

 current meters, it is expected that much progress also will be made 

 toward the development of a general-purpose current meter. In view 

 of these efforts by other agencies, it is recommended that the Hydro- 

 graphic Office not undertake any development of the electromagnetic 

 log at this time. 



F. REFERENCE 



VI- 1. JOHNSON, J. W. and WIEGEL, R. L. Investigation of current 

 measurement in estuarine and coastal waters. California. State 

 Water Polution Control Board. Berkeley. 233 p. September 1958. 



VI- 7 



