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Manual Sections
Background
Data Acquisition
Preparing to Run ARTOA-II
Program ARTOA-II
References
Glossary
Appendix A: Input/Output
Appendix B: Related Programs
Software Downloads
ARTOA-II
Email modules
Expect modules
Related Programs
Sample Files
Recent Changes
Changes
Relevant Links
Service Argos U.S. office
Service Argos head office
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PREPARING TO RUN ARTOA-II

Preparing Data for ARTOA-II
Program Pargot - now in Matlab Option to read Argos raw data directly into ARTOA-II TWO formats?

Preparing Parameters for Tracking
Program to acquire and format header information Program to create soso file

Before ARTOA-II can be run, information must be collected on the sound velocity in the experiment area, and on the drifts of the clocks in the sources and floats. Usually, the program that converts the float data from hexadecimal to "rfb" format computes the float clock drift by comparing the float clock time to the time recorded by the Argos data system when the float surfaces. <
BR> Sound source clock drifts can be determined directly by recovering the instrument and comparing its clock with standard time. They can also be computed by comparing the final TOA heard from that source by the float (converted to travel-time) to the distance between the float's surface location and the sound source. The accuracy of this calculation is dependent on the accuracy of the sound velocity used. Care should be taken extrapolating the float's location back to the time of the last TOA, as this also affects accuracy.

Another thing to consider is leap seconds one-second adjustments that are made to keep atomic clocks matched to astronomical time. The difference between a submerged clock (uncorrected) and a standard clock (corrected) will be affected. All leap seconds are positive, so if a leap second has occurred during an experiment, the difference between the two clocks should have one second subtracted from it. The website below keeps track of leap seconds: http://www.boulder.nist.gov/timefreq/pubs/bulletin/leapsecond.htm

Sound velocity can be calculated using ray-tracing programs, or by comparing the distance between a known float location (usually the launch location to minimize clock drifts) and source location and the travel-time between them. To use an a priori sound speed, specify the value in the Sound Source file select 'Sound.Source File' in the tracking-parameter window. Otherwise, ARTOA-II can compute the sound speed by several methods:

1. Del Grosso - uses the Del Grosso equation in the Matlab routine soundspeed.m to compute sound velocity from mean temperature and pressure (Del Grosso, 1974).

2. Linear - calculates the speed of sound by the linearized expression : sound_velocity = (average T - 7) *0.0011 + 1.49

3. Levitus - sound velocity computed from climatological data (Boyer and Levitus, 1994; Levitus et al., 1998) (Not implemented; defaults to 1500m/s)