Navigation 



Quality Control and Processing of Data 



Ships' positions were determined by celestial fixes 

 and dead reckoning. When near enough to shore, 

 radar was used to identify landmarks as a supplemen- 

 tary means. 



A summary of sampling activities conducted on the 

 vessels participating in the various cruises of JISETA 

 is presented in Table 1. 



Table 1.— Sampling activities on the Joint Investigation of the 

 Southeastern Tropical Atlantic. 



Goa Rockaway 



X X 



X 

 X 



X 



X 



X 

 X 

 X 



X X 



X X 



'Sahnity-temperature-depth recording systems. 

 Expendable bathythermograph 



Intercalibration 



During October, each vessel participating in JISETA 

 occupied a station near 12°20'S, 13°00'E, off Lobito, 

 Angola, for the purpose of intercalibration of physical 

 and chemical measurements. The results of these oc- 

 cupations are presented as comparative plots of 

 temperature vs. salinity and temperature vs. oxygen 

 (Fig. 2 and 3). The surface and near-surface values 

 were not plotted because of scatter in these data due to 

 real changes in the upper waters during the interval of 

 10 days between the first and last occupation of the 

 station. 



Determinations of temperature and salinity on the 

 three vessels were closely comparable; the T-S en- 

 velope width (Fig. 2) was 0.07°/oo and 0.3°C at its 

 widest point. Oxygen determinations on the floc/caway 

 and Undaunted were not as comparable. In warmer 

 water (>9°C) above 150 m the determinations were 

 widely different, possibly because of real changes in 

 concentration; the depth of the oxycline varied widely 

 in space in the vicinity of the intercalibration station. 

 However, the oxygen determinations were closely 

 comparable in cooler water (<9°C) in and below the 

 oxygen minimum. 



Each agency participating in JISETA was indepen- 

 dently responsible for shipboard and laboratory qual- 

 ity control of the data it collected, using the methods 

 listed in Table 2. 



DATA PROCESSING 



The vertical sections presented in this report were 

 produced from data derived from bottle casts and STD 

 instrument lowerings. All data obtained were reduced 

 and quality controlled by the participants. Final pro- 

 cessing and quality control were completed by the 

 U.S. National Oceanographic Data Center (NODC). 

 The data were archived by NODC and are available to 

 interested persons from NODC under the following 

 identification: 



Standard depth interpolation for temperature, salin- 

 ity, and oxygen was based upon a 3-point Lagrange 

 interpolation equation (Scarborough, 1958). Details of 

 this interpolation method are available from NODC. 



Following interpolation, the data were edited and 

 anomalous data were examined for validity by com- 

 parison with data acquired at nearby stations as well 

 as with historical data from the same region. When 

 validity was doubtful, data were flagged. In the prep- 

 aration of this report, data of doubtful validity were not 

 used for development of the vertical sections. 



Several stages in the process by which the JISETA 

 data were impressed into the standard NODC format 

 may be of interest to anyone concerned with applica- 

 tion of the final product. These stages are described 

 below. 



All data were subjected to the standard NODC sta- 

 tion data compute program. In this program, values of 

 temperature, salinity, and oxygen were interpolated at 

 standard depths between the observed values, using 

 the routine shown in Appendix 1. 



All data were subjected to edit programs which flag 

 anomalies such as impossible ship-location/time se- 

 quencesand improbableorunprocessable parameter 

 values, to be corrected in the next stage by an 

 oceanographer/monitor. More significantly, when the 

 value of sigma-f (both observed and standard-depth 

 values) was less than the value at the depth im- 

 mediately above by an amount exceeding 0.02 

 sigma-f units, it was flagged. 



