averaging technique will maintain the basic profile structure without distortion, 

 and will provide a more accurate picture than the normal averaging of isothermal 

 charts or isodepth charts. This technique can either be a visual one or a mathematical 

 one. 



9.5. Establishing Average Trends 



There are many instances of study where long range trends are desired. These 

 long range trends can be obscured by the individual variations such as standing 

 waves, spurious data, etc., which are of short-term duration. In its place an average 

 trend is desired which minimizes or eliminates these short-term variations. 



The technique employed to establish an average trend is to establish a series of 

 average Bathythermograms from which the average trends can be taken. The ques- 

 tion arises as to the length of time over which an average should be made. Since for 

 any average Bathythermogram which is desired the average or standard deviations 

 can be obtained, the duration over which the Bathythermographs are averaged should 

 be such that the deviations of the average Bathythermogram should not exceed the 

 minimum differential which is desired in establishing the trend. If at any time the 

 deviations of the average Bathythermogram are greater than the desired differen- 

 tial in trends, these trends have no mathematical significance, and should either be 

 ignored or reworked with a smaller average Bathythermogram. 



It should be noted that the average Bathythermogram which is made will pro- 

 duce erroneous or distorted results unless obtained as described in Section 9.3. 



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