various types of salinity bridge has been carried out by the 
Naval Oceanographic Office. Not only will Ocean Surveys take 
advantage of the results of such tests, but through the ICO 
Ocean Surveys Advisory Panel and the various participating 
agencies other comparable intercalibrations will be carried 
out to insure compatibility “olf results j= These iefforts- will 
of necessity be coordinated with international tests designed 
to- insure the same results on an international basis. 
i’, Navigation 
For an effective program of Ocean Surveys, the availse- 
bility of an accurate means of positioning a ship anywhere 
at sea is a basic prerequisite. Samples and measurements 
taken at sea are only of limited value without accurate 
knowledee of the location at which they were obtained. 
In the past, considerable oceanographic work has been 
accomplished using the time-honored but relatively inaccurate 
techniques of celestial navigation and dead reckoning. for 
some operations at sea, particularly measurements of those 
fectors ‘chats vary. so rapldily with’ time that: their absolute 
geographic position is relatively unimportant, these methods 
have been adequate. However, for accurate mapping, partic- 
ularly of those time-independent variables such as bottom 
topography, sediment distribution, and spatial variations in 
the gravity and magnetic fields, accurate position control 
is absolutely essential. 
