Water Column page
To achieve correct echo information, the current environmental parameters must be known to the SN90 system. The Water Column page collects these parameters. These must be defined to match the current conditions.
This page is opened from the Environment dialog box. The Environment dialog box is opened from the Setup menu.
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Description
You must correctly set the sound speed through the water to obtain accurate depth readings and fish echoes. Several parameters are required to calculate the correct sound speed value. If these parameters are unknown, use the default value of 1494 m/s. This is a typical mean value for sound speed in salt water.
Details
Conditions
Use these settings to set up the SN90 system for operation in fresh or salt water.
Sound travels at different speeds in salt and fresh water. For this reason, the SN90 system must know your water profile. The default setting is Salt.
Parameters
Use these settings to provide manual values.
Freshwater/saltwater settings, temperature, salinity, acidity, depth, and operating frequency are all used to calculate absorption.
Temperature
Specify the water temperature. Once the salinity and temperature information is provided, the SN90 system calculates the sound speed and absorption.
Salinity
Provide the current salinity. Once the salinity and temperature information is provided, the SN90 system calculates the sound speed and absorption.
Sound Speed
You must correctly set the sound speed through the water to obtain accurate depth readings and fish echoes.
Calculated
Select Calculated to allow the SN90 to calculate the sound speed and absorption based on your supplied parameters (frequency, salinity, acidity sound speed, and water temperature).
Manual
Select Manual to provide a sound speed value manually. A value provided manually can be relevant if neither a sound speed sensor nor a CTD (Conductivity Temperature Depth) sensor is available.
Absorption
The absorption curve is calculated and drawn using the parameters provided.