About filesets

Filesets and EV files

An EV file can contain a single fileset or multiple filesets of added data. You will find multiple filesets useful if you work with:

Echosounders or logging software, such as the Simrad BI500, that log data from multiple transducers into separate data files.
Data logged from multiple echosounders at the same time.
Text data file added to the EV file.
Unrelated video files.

Filesets and data files

Each fileset can contain a single data file or multiple data files. The following rules apply:

A fileset may contain data files of a single type (file extension) only.
Note: HTI .smp files for HTI data are an exception to this rule.
All .ek5 files in a fileset must be associated with the same type of echosounder.
Some files types require that related data files are available for Echoview to read. Check the support details for your data file format.
Filenames and file ordering are interrelated. See Ordering of data files for more information.

Deriving raw variables

Hydroacoustic data may be logged under a transducer number, transducer frequency, channel number, or a combination thereof. The transducer or channel number may be based on the order in which the device was connected to the data logger. When Echoview reads a data file, it tries to identify the transducer or channel number. For some file formats Echoview may be able to identify data associated with transducer frequency.

Derive raw variables on the Fileset Properties dialog box allows you to specify a method to derive raw variables that best suits your data. Saved EV files and EV template files have derived raw variables, and derived raw variables are used with virtual variables and virtual variable chains.

Available methods:

Using transducer/channel number

The Using transducer/channel number method reads data file transducer/channel number to derive raw variables. Pre-Echoview 9 EV files are assigned this method when the EV file is opened.

Using transducer frequency

The Using transducer frequency method considers transducer frequency when deriving raw variables.

Data mapping by transducer frequency can only be applied to Simrad Ex60 (includes file formats based on Simrad Ex60 file format), Simrad EK80, BioSonics DT4, ASL Environmental Sciences AZFP and Echoview EVD data files. New EV files are assigned this method by default.

The Using transducer frequency method may be useful where data file transducer frequency causes problems for derived raw variables output under the Using transducer/channel number method.

Notes:

Data mapping by transducer frequency cannot be applied if a data file contains two or more identified transducers with the same frequency. The transducer/channel number will be used instead. On the Fileset window, Variable names may include a transducer number, however, those Variables on the Dataflow window may be displayed under a different transducer object to avoid a naming conflict.
Data mapping by transducer frequency cannot be applied if a data file contains an identified transducer with more than a single frequency associated with it. The transducer/channel number will be used instead. An exception for this occurs for variables derived from Nortek pulse compressed data.
When attempting to populate the transducer and platform object fields from transducer offsets loaded from data files, Echoview will no longer warn the user for an existing object (e.g., X-, Y-offsets, or Z-offsets if only transducer depth is available) if it does not match those read from the data file.

Transducer number is swapped

Consider the case where data files record inadvertently changed transducer numbers but the transducer frequencies remain the same:

During survey A, transducers are attached to the transceiver as T1 38kHz and T2 120kHz.
During survey B, the same transducers are used but the transducers are attached to the transceiver as T1 120kHz and T2 38kHz.

An EV file is developed using the data files of survey A. Virtual variables are created to handle frequency-specific raw and virtual variables.

If the EV file uses the Using transducer/channel number method, only the transducer number is used to derive raw variables. When survey B data files are added to the fileset:
- the T1 raw variable is assigned pings recorded under the T1 transducer number, however the ping frequency is incorrect with respect to survey A
- the T2 raw variable is assigned pings recorded under the T1 transducer number, however the ping frequency is incorrect with respect to survey A
- frequency-specific virtual variables will require manual reconfiguration
If the EV file uses the Using transducer frequency method, transducer frequency is used to derive raw variables. When survey B data files are added to the fileset:
- the T1 raw variable is assigned pings of 38 kHz, even though they are recorded under the survey B, T2 transducer number
- the T2 raw variable is assigned pings of 120 kHz, even though they are recorded under the survey B, T1 transducer number
- frequency-specific virtual variables use data of the correct frequency

Additional transducers/frequencies

Consider the case where additional transducers are introduced with an additional frequency between existing frequencies:

During survey C, transducers are attached to the transceiver as T1 38kHz and T2 120kHz.
During survey D, transducers are attached to the transceiver as T1 38kHz, T2 70kHz and T3 120kHz.

An EV file is developed using the data files of survey C. Virtual variables are created to handle frequency-specific raw and virtual variables.

If the EV file uses the Using transducer/channel number method, only transducer number is used to derive raw variables. When survey D data files are added to the fileset:
- the T1 raw variable is assigned survey D, T1 38 kHz pings.
- the T2 raw variable is assigned survey D, T2 70 kHz pings. The survey D, T2 transducer frequency (70 kHz) does not match the survey C, T2 transducer frequency (120 kHz).
- a new T3 raw variable is assigned survey D, T3 120 kHz pings.
- virtual variables for the expected T2 120 kHz variable will require manual reconfiguration because 120 kHz pings are under the derived T3 raw variable
If the EV file uses the Using transducer frequency method, transducer frequency is used to derive raw variables. When survey D data files are added to the fileset:
- the T1 raw variable is assigned survey D, T1 38 kHz pings
- the T2 raw variable is assigned survey D, T3 120 kHz pings
- a new T3 raw variable is assigned survey D, T2 70 kHz pings
- virtual variables for the T2 120 kHz raw variable use data of the correct frequency

Dataflow window transducers

The Fileset Properties dialog box setting Create and/or associate transducers based on frequency when new raw variables are derived can be used to create transducers based on transducer frequency. The setting can be used with either Derive raw variables method. A transducer created under this setting displays transducer frequency and fileset information on the Dataflow window and in the Transducer Properties dialog box.

If frequency mapping is turned off (ie., by de-selecting the tick box for Create and/or associate transducers based on frequency when new raw variables are derived), transmission characteristic variables are then created under a new autogenerated transducer. However, both transducer and platform objects created in non-frequency mapped filesets are totally excluded from warnings.
Warnings will be triggered when values manually inputted into a dataflow object (e.g., transducer and/or platform) do not match values for those objects in the fileset. The warning will guide the user to fix the issue(s) in the Transducer Properties dialog box.