Processing of Digital Data Logger STD Tapes 



at the 



Scripps Institution of Oceanography 



and the 



Bureau of Commercial Fisheries, 



La Jolla, California 



By 

 JAMES H. JONES, Oceanographer 



Scripps Institution of Oceanography 

 La Jolla, California 92037 



INTRODUCTION 



As part of the EASTROPAC Survey Pro- 

 gram, computer programs were developed to 

 process STD (salinity-temperature-depth) data 

 from Bisset-Berman model 9006 systems," and 

 record them on incremental IBM compatible 

 DDL's (digital data loggers), also manufactured 

 by the same company. The accuracy and pre- 

 cision of these two instruments are described 

 in the manufacturing brochures and are not 

 discussed here. During the EASTROPAC Pro- 

 gram, about 10,000 m. of field tapes were 

 generated which required editing and data 

 processing. 



The purpose of this paper is to describe 

 the methods developed for processing the field 

 tapes to a point where the data produced from 

 them may be compared with some independent 

 calibration such as conventional Nansen casts 

 or Niskin samplers, attached to the STD's. 



In its present form, the DDL samples each 

 of four channels of information about once 

 every 0.2 second, and writes a seven-channel 

 IBM compatible tape at a bit density of 200 

 bits per inch. At a drop rate of 60 m. depth 

 per minute, salinity, temperature, depth, and 

 the optional sound velocity channel are sam- 

 pled five times in each 1-m. interval. Since the 



uncertainty of the depth sensor is about 1 m., 

 at this maximum sampling rate, five values of 

 temperature and salinity are available to pro- 

 duce one value per meter. The program de- 

 scribed below is based on the premise that the 

 original field tapes are recorded at this maxi- 

 mum rate. Slower sampling rates require slight 

 modification of the low-pass filters used in the 

 program. The fourth and optional channel of 

 sound velocity is not used on any STD systems 

 of the Scripps Institution of Oceanography, or 

 the Bureau of Commercial Fisheries; therefore 

 no description of schemes to process the op- 

 tional channel is included. 



PRELIMINARY PROCESSING 



When the, field tapes are received at the 

 data-processing center they are first passed 

 through a computer routine which examines 



l\Vork for this manuscript was done while the 

 author was employed by the Bureau of Commercial Fish- 

 eries Fishery-Oceanography Center, La Jolla, Calif. 

 92037. 



^Use of trade names does not imply endorsement 

 by the Bureau of Commercial Fisheries. 



