User`s manual

Appendix IV: Derived Parameter Formulas
86
average sound velocity = [m/s]
Average sound velocity is the harmonic mean (average) from the surface to
the current CTD depth. The average is calculated on the downcast only. The
first window begins when pressure is greater than a minimum specified
pressure and salinity is greater than a minimum specified salinity. Depth is
calculated from pressure based on user-input latitude.
• In SEASAVE and in SBE Data Processing’s Data Conversion module, the
algorithm also requires user input of a pressure window size and time window
size. It then calculates:
d
i
= depth at end of window – depth at start of window [meters]
v
i
= (sound velocity at start of window + sound velocity at end of window) / 2 [m/sec]
• In SBE Data Processing’s Derive module, the algorithm is based on the
assumption that the data has been bin averaged already. Average sound
velocity is computed scan-by-scan:
d
i
= depth of current scan – depth of previous scan [meters]
v
i
= sound velocity of this scan (bin) [m/sec]
Surface
> Minimum specified pressure and salinity
d
i
and v
i
Average
sound velocity
Average
sound velocity
d
i
and v
i
Σ
d
i
∆
p,p=min
p=p
Σ
d
i
/ v
i
∆
p,p=min
p=p