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might be re-designed such that the arm and center sensors are also at 

 the same elevation above the seafloor. However, for the first DPG 

 prototype, the nine inch difference in height between the sensors 

 leads to very small error in the calculation of an average pressure 

 response function used in the development of the water surface slope 

 terms. (See Section III.C.2.) In water depths as shallow as 10 feet 

 (3.1 m) , the error is still small — less than three percent for 

 waves of three second period. 



The instrument might be re-designed such that the lengths of 

 each tubing used in the sensor systems are identical. This would 

 help ensure that the response time of each channel is identical and 

 that there is no difference in response time for the loading of an 

 arm sensor compared to a center sensor. This would eliminate 

 differential pressure drift induced by changes in ambient 

 temperature, thus disabling the instrument to measure ambient water 

 temperature. 



The arrangement of the transducers inside the water-tight 

 cylinder might be re-designed to allow servicing of individual 

 pressure transducers without the need to bring the entire 

 instrument to the surface. Such a design change could, however, add 

 additional problems to the dependability of the transducers since 

 this would most probably require the addition of underwater-pluggable 

 connectors for each transducer. The present instrument utilizes one 

 such connector that is mated only above water in routine maintenance. 



