Calibration settings for EK500 telegrams logged with Ex500

This page describes the settings, necessary to an Echoview calculation, on the Calibration page of the Variable Properties dialog box for acoustic variables derived from Ex500 data files.

We recommend you assess the suitability of the settings available on the Calibration pages for each acoustic variable. Some settings will be used to calculate datapoint values or ranges, others may be used during analysis or display of the data. The tables below show which settings are used for calculating datapoint values and ranges and which are used for other calculations. The tables also detail the parameters that are read from the data file and used to calculate range values.

Quantitative calculation/analysis requires calibrated data which is achieved using correct calibration setting values (rather than default values). An ECS file enables you to modify calibration settings for variables in a fileset.

Notes:

• The (red) default values on the Calibration pages are for illustration purposes only and have not been read from your data file. Read About calibration settings for further information.
• This data may have one calibration source however calibration settings available under the calibration source may not be available (or used) by every raw variable.

Table legend:

• Simrad sample variables logged with Ex500
  • Sv and TS from Power (W telegrams) and B telegrams logged with Ex500
  • Sample Sv and TS variables (V and P telegrams) logged with Ex500
• Simrad echogram and echo trace (Q and E telegrams) variables logged with Ex500
• Specific Simrad Ex500 setting details

Simrad sample variables logged with Ex500

Sv and TS from Power (W telegrams) and B telegrams logged with Ex500

Sample Sv and TS variables (V and P telegrams) logged with Ex500

It is possible to apply calibration correction to Sample Sv and Sample TS variables. How the settings are used depends on whether calibration correction has been applied.

Simrad echogram and echo trace (Q and E telegrams) variables logged with Ex500

It is possible to apply calibration correction to echogram and echo trace variables. How the settings are used depends on whether calibration correction has been applied.

Notes:

• Myriax recommends logging data with transducer depth set to 0 on the Ex500 as the embedded draft that is otherwise created reduces the number of samples in the echogram telegram, see logged draft warning for more information.
• Not all telegram types can be logged by all Ex500 echosounders.

• Wavelength in the Ex500 is calculated from the nominal frequency using a sound speed of 1470 meters per second (Haakon Solli, Simrad, pers. com.) - this does not appear in Simrad user manuals. Changing the sound speed on the Calibration page does not change wavelength.
• Settings available under the calibration source may not be available to or used by every raw variable. Telegrams that are described together may be affected by the settings that they have in common.

See also

About calibrating data

Specific Simrad Ex500 setting details

Start sample range

Enter the start range of the sample data in meters.

Note that for EK500 v. 5.3 and higher, this must be 0 meters. For EK500 v. 5.2 and earlier, use the start depth of the "super layer".

Sample resolution

The sample resolution can be determined from the nominal frequency of the transceiver card. The following table provides sample resolution for common Simrad transducers according to the Simrad EK500 manual (V5.3).

Note that the sample resolution is constant in distance even if a sound speed profile is entered. The algorithm used by Simrad to calculate sample values at fixed distances, given data sampled at fixed time intervals, is not documented in the EK500 manual. Contact Simrad for details.

If it is desirable to process at a different sound speed than the sound speed that the data were logged with then it is necessary to change the sample resolution.

There is a simple relationship between sample resolution and sound speed, when the Ex500 was run with a constant sound speed over the data depth range:

New sample resolution = old sample resolution * new sound speed/old sound speed

Apply Simrad TVG range correction

The Ex500 series of echosounders apply a correction to the time-varied gain calculated for each sample point to compensate for electronic delays in filter circuits.

If applied, the time-varied gain applied at each sample depth, when calculating Sv from power, is calculated using a corrected range, rather than the actual range to the sample.

See EK500 Power to Sv and TS for further details.

The reason for this type of range correction is discussed in Simmonds and MacLennan pp. 118. Also see About Time Varied Gain.

If range correction is not applied, the time-varied gain, applied in calculating Sv, is calculated using the range of each sample.

See also

About calibration settings Entering calibration settings
Simrad data files
Raw variables derived from Ex500 data
EK500 Power to Sv and TS
Simrad angular position calculations

Echoview Help file 5.2.21 for Echoview 5.2.55 Monday 21st May 2012

Please report any errors or omissions to support@echoview.com.