The Representation of Oceanic Movements and Kinematics 



347 



47»3a' 



47''37' 



47« 36'W 



47«>35' 



l2°3gN 



2138' N 



I2»37' 



47" 38' 



4r3r 



47''36 W 



47° 35' 



Fig. 141. Successive positions of the ship, ship's course and circle of yaw at the anchor 

 station 288 of the "Meteor", 27-29 March 1927. 



+ The computed longitude of 47° 37-7' W. is very probably an error; 36-7' W. should be 

 the correct value. 



modilied the method by using a sounding line to obtain a fixed point at the sea bottom, 

 but this can only be used in very shallow waters. 



According to Witting, the best, fastest and also the most frequently used method is 

 the "'smoothing method''. The current measurements are made from an anchored vessel 

 at the shortest possible intervals and values for a time interval over which the different 

 movements of the ship almost cancel out are combined to give a mean vahie. An 

 interval of about 1 5-30 min seems to be sufficient to eliminate the variations due to 

 the movements of the ship and irregular changes in the current direction and speed. 



(d) The Scientific Use of Current Measurements 



The technical refinements of the operative mechanism of the amazingly large 

 number of current recorders used in oceanography need not be discussed here; 

 reference can be made to Thorade (1938^), Sverdrup and co-workers (1946) and 

 particularly to Oceanographic Instrumentation Isaacs and Iselin, 1952). However, 

 the important subject of the scientific use of current measurements will be dealt with 

 here in greater detail. 



