SECTION 9.0 



PROPOSED METHODS FOR DISCOVERING, EVALUATING, 



AND MINIMIZING ERRORS IN EXISTING AND 



FUTURE BATHYTHERMOGRAPH DATA 



The recognition and classification of the various sources of error which are involved in the 

 collection and processing of Bathythermograph data provides definite indications as to meth- 

 ods of attack for evaluating and minimizing these errors when employing these data for 

 theoretical studies. 



These techniques for minimizing errors must bear a direct relationship to the use to which 

 the Bathythermograph data is to be put. For instance, should the study only require a knowl- 

 edge of temperature differences between one depth and another, it is not necessary to be 

 concerned with the absolute values which the Bathythermograms represent. On the other hand, 

 should the studies be concerned with the variability of the ocean with respect to time, then all 

 variations in correction factors must be eliminated, or at least minimized as best one can. 



Minimization of the error in reproducibility in the Bathythermograph lies for the 

 most part in experimental investigations. Such investigations will not be taken up here, 

 but suggestions will be found in Section 10.0, Recommendations. On the other hand, mini- 

 mization of errors in Bathythermograph sets lend themselves to mathematical studies. These 

 are taken up in detail below. 



9.1. Establishing the Reliability of the Surface Temperature Correction Technique 



9.1.1. Use of Trend Charts 



Visual comparison of the variations and trends in the bucket or injection tem- 

 peratures as compared to the uncorrected zero depth values for the corresponding 

 Bathythermograms is one of the best methods for determining the reliability of 

 correcting the Bathythermograph sets by this independent measurement. 



When sudden changes or discontinuities appear in the trend charts, three pos- 

 sibilities are evident : 



(1) A change has occurred in the set of the BT (noted by a change in the 

 zero-depth plot which is not followed by a corresponding change in the 

 bucket temperatures) . 



(2) A change has occurred in the injection thermometer, due to error of read- 

 ing, or failure of the instrument (noted by discontinuity in the bucket 

 temperature plot not observed with the Bathythermograph zero depth 

 values) . 



(3) A change has occurred in both curves, representing a decided change in 

 ocean conditions. 



The degree of "randomness" can be observed in both curves, which is a good 

 indication as to the relative accuracies of both instruments. Where the random- 

 ness of the bucket temperatures is small compared to that of the zero depth value 

 of the Bathythermograph, then this is good indication that individual, rather than 

 average, correction factors be applied. If the converse is true, then average correc- 

 tion factors are better. 



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