Manual

June 2004 Isis® Sonar User's Manual, Volume 2 118
After the serial port information has been received, the following steps are performed:
1. If a manual depth has
not been set (in Configure, Transducer Depth), and
pressure has been received, then towfish depth is computed from pressure
according to the following formula:
Depth = 0.6868 • pressure + calibration
The calibration is set in the file
ISIS.CTD, variable DK, which allows for zeroing-
out the depth computation on deck. This is the only value used from the
ISIS.CTD
file when using a Falmouth Scientific (or any other non-SeaBird) CTD.
2. If sound velocity has
not been received, and temperature, pressure and
conductivity
have been received, then the speed of sound in water is computed
according to the Chen-Millero formula.
3. If saving data in SEG-Y format, the values are saved in the first channel’s binary
trace header as follows (first byte in header is byte 0):
Table G-5. Falmouth Scientific’s CTD SEG-Y format values in the first channel’s binary
trace header (CTD raw data, where first byte in header is byte 0)
short
Turbidity bytes 216-217 Turbidity sensor, volts times 10000
Table G-6. Falmouth Scientific’s CTD SEG-Y format values in the second channel’s
binary trace header
long
Conductivity bytes 200-203 Conductivity in Siemens per meter, times
100000
long
Temperature bytes 204-207 Temperature in degrees C, times 1000
long
Pressure bytes 208-211 Pressure in psia, times 1000
long
SoundVelocity bytes 212-215 Computed speed of sound, times 100
See the file
SEGYFMT.H for more info on how Isis uses the SEG-Y data format.
4. If saving in Q-MIPS format version 1.51 or later, the values are saved as follows:
Appendix G: How Isis Processes CTD Data