echoview

Calibration

Echoview's new calibration model brings you calibrated data quickly and painlessly, no matter which sounder you're using.

On this page

# A new calibration model
# Apply calibration parameters via the data file
# Apply calibration parameters via an ECS (supplement) file
# Converting older Echoview files to the new model
# Supported data formats

A new calibration model

Calibration parameters are sounder, location and time-specific. Echoview's new calibration model now enables you to store your sounder's parameters in a single location-/time-specific place, saving you time and minimizing room for error.

What is calibration?

Calibration is critical for quantitative analyses. It is the process by which calibrated data (absolute backscatter at corrected range and time) are calculated from raw data (received echo power at logged range and time):

Calibrated data = raw data + calibration parameters

Calibration parameters

Calibration parameters include environmental variables (sound speed and absorption coefficient) and sounder variables (transmitted power, gain, beam angle etc.).

Environmental variables relate primarily to temperature and salinity, which change over space and time. Sounder variables relate to temperature (which changes over space and time) and the characteristics of the hardware (which can change over time).

Calibration parameters are therefore sounder- and location/time-specific.

Out with the old, in with the new

In Echoview versions 4.90 and older, calibration parameters were defined and documented at the variable level. As the model below shows, there were therefore multiple places in which the same sounder-related information could be held.

Versions 4.90 and older
Sounder > EV files (Filesets) > Raw Variables > Virtual variables

In Echoview version 5.00, calibration parameters are defined and documented at the sounder level. As the model below shows, there is now a single place in which the sounder-related information is held.

Version 5.00
Sounder (ECS file) > EV files (Filesets) > Raw Variables > Virtual variables

What are the benefits?

The benefits of having one place for all your calibration parameters are clear:

• Save time
  Change the values in one place and they propagate painlessly to any EV files that reference these parameters.
• Minimize human error
  No need to go through and manually check multiple EV files.
• Share metadata easily
  Store your calibration parameters in a single location on a fileshare, or quickly email individual calibration metadata files as required.

Two ways to calibrate with the new model

In Echoview version 5.0 you define, document and apply your sounder's location-/time-specific calibration parameters in two ways:

• Via the data file (where supported, see below).
• Via an Echoview Calibration Supplement (ECS) file.

Apply calibration parameters via the data file

Your data are automatically calibrated upon loading (and you don't need to do anything else) if both of the following are true:

• Your data files have been logged by your sounder with the correct calibration parameters.
• Echoview can read calibration parameters from your data files (see below).

If one or both of these are not true, you will need to create and apply an Echoview Calibration Supplement (ECS) file.

How do I know which parameters are being read and applied to my variables?

You can verify the parameters that are being read and the values being applied by looking at the Variable Properties window of a variable.

The Variable Properties > Calibration dialog shows which calibration parameters are being applied. Check that the "Value" figures are as expected based on the numbers that are being read from the data ("Data file") and which from an ECS file ("Calibration file"). In the absence of either, Echoview applies a default value and shows it in orange.

Please see the help file that is installed with Echoview 5.0 for further details on calibration parameters. 

Apply calibration parameters via an Echoview Calibration Supplement (ECS) file

NOTE: See also the Echoview v5.0 Help file page "Echoview calibration supplement files" for further information.

You will need to use an Echoview Calibration Supplement (ECS) file if one of the following is true:

• You wish to override some or all of the calibration parameters being read from your data files.
• Echoview can't read the calibration parameters from your data files (see below).

An ECS file is a simple text file that you can open and edit in an editor such as Notepad.

TIP: You can set your operating system to open ECS files in whichever editor software you choose via the Right-click > Open with... menu in Windows Explorer.

Create an ECS file

Echoview provides a utility for creating ECS files. Once the data are loaded, simply click the "New" button on the Calibration bar of the Filesets window.

An annotated ECS file based on your datafile format will then open in the editor of your choice.

The structure of an ECS file

The ECS file created by Echoview is annotated and divided into three sections. These sections follow a hierarchy that defines how the parameters are applied:

• Fileset settings
  For adjusting the calibration parameters of all variables in a given fileset. Settings in the Fileset section override settings read from the datafile or applied as a default by Echoview.
• SourceCal settings*
  For adjusting the calibration parameters of all variables in a given fileset that are associated with a given SourceCal*. Settings in the SourceCal section override Fileset settings, plus settings read from the datafile or applied as a default by Echoview.
• LocalCal settings*
  For adjusting the calibration parameters of all variables in a given fileset that are associated with a given LocalCal*. Settings in the LocalCal section override Fileset and SourceCal settings, plus settings read from the datafile or applied as a default by Echoview.

*SourceCal and LocalCal

A SourceCal (or "calibration source") is a discrete collection of calibration parameters that is defined and named in the datafile itself (e.g. "T1", "formed pings" etc.). Echoview uses information about the data file to automatically assign each variable to a SourceCal. The SourceCal is noted in the Variable Properties > Calibration dialog and generally correlates to the end of the variable's name.

A LocalCal is also a discrete collection of calibration parameters, but unlike SourceCal it is defined by the user rather than logged in the datafile. Importantly, a variable that is associated with a given LocalCal will also remain associated with its pre-defined SourceCal. This means it can take values from both a SourceCal and a LocalCal. Any LocalCal sections in your ECS file require an identifying header line.

Edit and apply an ECS file

Simply enter the desired parameters and their values into the relevant sections of the ECS file.

Lists of calibration parameters and their syntax are available in the Echoview v5.0 Help file; a good place to start is the "Common calibration names" page. You can also copy and paste the parameters directly from the Variables Properties > Calibration window.

To apply your chosen parameters, save the ECS file. Check that the variable is using the appropriate calibration set in the Variable Properties > Calibration dialog. It will default to its pre-defined SourceCal (and apply any SourceCal values in the ECS file) unless you specify a LocalCal (if available).

The ECS file will show in the Calibration bar of the Filesets window as linked to the fileset in which it was created. To re-open and edit further, click on the "Edit" button. To add a different ECS file, click on the "..." button.

Please see the help file that is installed with Echoview 5.0 for further details on editing and using ECS files.

Working with older Echoview (EV) files in version 5.0

A whole new way of working with your data

The radical change to a centralised and vastly simplified calibration model brings with it a whole new way of working with your data.

If you wish to continue working with EV files created with an older version of Echoview, no problem at all:

• Auto-calibrate from the datafiles
  If your data were logged with the correct calibration parameters and Echoview can read these from the datafiles (see below), then you don't need to do anything! When you open your older EV file in version 5.0, your data are automatically calibrated for you.
• Point your EV file to an ECS file
  If your original EV file contained calibration parameter overrides, simply create an ECS file that contains these overrides and then point your Fileset to it. Remember that you only need to create one ECS file per sounder/location/time, to which you can then point as many Filesets in EV files as you like.

The Historic Calibration utility

The Historic Calibration utility is there to help you when first creating your various sounder-/location-/time-specific ECS files.

Select Help > Historic Calibration and browse for an existing EV file that contains a record of the calibration-parameter overrides for your sounder. These parameters and their values will be read from the file and displayed in the window below, ready to be copied and pasted into your new ECS file as required.

What if I wish to work with many older EV files in version 5.0?

Beyond a certain number of EV files, it may become laborious to manually repoint each one to a corresponding ECS file. In this case, you can automate this process via COM automation (Scripting). COM methods and properties are available for this - please contact Echoview Support for more information on how to do this.

If you wish to automate this process and don't have access to a licensed copy of the Scripting module, please contact Echoview Support.

Supported data formats

Reading from the datafile

Echoview can read and apply the calibration parameters from the following datafile formats:

• Simrad RAW (Ex60, ME70)
• BioSonics DT4
• HTI raw sample (.SMP)

We will add support for other data formats in subsequent Echoview releases.

ECS files

You can create an ECS file for any data format that is currently supported by Echoview.