ASL Acoustic Profiler Time Series

Data products for ASL Environmental Sciences echosounders are described here. Currently, three echosounder types are supported: the Zooplankton Acoustic Profiler (ZAP), the Acoustic Water Column Profiler (AWCP) and the Acoustic Zooplankton and Acoustic Zooplankton Fish Profiler (AZFP). The Shallow Water Ice Profiler (SWIP) is a similar instrument, however it only reports ice draft scalar data, not echosounder backscatter; SWIP data is available via scalar data products. Echosounder backscatter data is numerically intense, generating some of the largest data sets at ONC. Because of this, ASL echosounder data products for extended time ranges will be slow to generate and download. In addition, ASL echosounders produce ancillary scalar data, such as temperature, pitch, roll, which are available independently as scalar data products or via Plotting Utility.

ONC has worked closely with ASL Environmental Sciences, providing a testbed for the development of their echosounders, especially for their calibration. Users may notice that the ZAP is the simplest of the echosounders, while the AZFP is the most advanced. This is reflected in the MAT file product as MAT files from the ZAPs have a number of empty fields. In order to create a MAT file product that works with as many echosounders as possible, including multi-frequency AWCPs and AZFPs, the format and layout of the MAT file is more complex then the original ZAP mat file format available on the VENUS data download page. Users of ZAP data from the VENUS data download page will find more information on the more generic ASL MAT file format below, including a matlab script that can be used to convert MAT files into the VENUS ZAP format. The script is also useful as a guide for users to update their code to the new file format. Once updated, users can process ASL data from a combination of ZAP, AWCP and AZFP echosounder over a long time range, seamlessly. (ZAPs are slowly being phased out in favour of AZFPs.)

EchoView is a popular data analysis and visualization software for echosounders. There are two data product formats that EchoView can read: ASL EchoView export CSV and ASL's binary format .01a file, both of which are described below.

ASL manufacturer's documentation:


(Note that these are static - newer versions maybe available and may not be updated here. Contact us or ASL for the latest documentation.)

AZFPlink and similar manufacturer's software for ZAP and AWCP is available from ASL, see their website:

For internal users, additional useful information, data, files, etc, maybe found in Alfresco: ASL device documentation.

Oceans 2.0 API filterdataProductCode=AAPTS

Revision History

  1. 20110302: Beta MAT product released
  2. 20141028: Major revision: support AZFP and AWCPs, integrate options, process requests from all networks, improve performance, standardize MAT files, add plots
  3. 20150504: Major revision: add support for ZAPs, add sun elevation graph
  4. 20191204: Add ASL EchoView export format CSV files, add Target Strength calculation, add Noise Suppression option
  5. 20200107: Add ASL (manufacturer's) binary format .01a file (with xml configuration files for EchoView integration)

Data Product Options


Processed data is available in MAT, CSVPNG and PDF formats. The manufacturer's raw binary format, 01A, is also available. It replicates the nominal way of acquiring data from autonomous / stand-alone devices. Both it and the CSV file format can be loaded into popular visualization software EchoView (link). The CSV format replicates ASL's data export from their software, with options for Volume Backscatter and Target Strength output. The MAT, PNG and PDF file/plots (respectively) are general purpose and also have the same options as the CSV export format. Further content descriptions and examples are provided below. 

When a driver/device restart is detected, the configuration is checked and if the configuration changed, all data products will break and a new file will be started (configuration breaks are also noted in the search status and logs). For all non-averaged data products and daily plots, a new file is started at the start of each day (in addition to configuration breaks). For ensemble-averaged MAT/CSV files and multi-day plots, the files can extend over multiple days, while file breaks will still occur for configuration changes and if the files get too big (MAT/CSV files will break if they occupy more than 1 GB of memory). 

Calibrated data are represented in Volume Backscatter strength in units of dB re 1 m-1 or in Target Strength in units of dB re 1 m2. Without calibration, the data is in units of raw counts which is proportional to the pressure amplitude. When plotting raw data, the data is still plotted in a dB scale relative to the full scale of the device, where 0 dB represents the maximum value, normally 65535 raw counts for 16 bit data, and the lowest value is the 20*log10 value of the smallest value the A/D converter will produce (about -48 dB for ZAPs, about -96 dB for AWCPs and about -120 dB for AZFPs). Details on the calibration algorithm and formulae can be found here: (hard copy here: EchoViewManual_AZFP_Sv_and_TS.pdf). 

For multi-frequency echosounders with separately mounted transducers, we account for the height variances with the device attribute Echosounder_TransducerHeight, which is utilized in both the plots and presented in the Meta structure in the MAT files.

Data files: MAT

MAT files (v7) can be opened using MathWorks MATLAB 7.0 or later. The file contains four structures: Meta, Data, Config, and Units. The structures are the same for AWCP, AZFP or ZAP ASL echosounders. Data Search / Oceans 2.0 ZAP MAT files can be converted to the VENUS ZAP format (no longer available) by a conversion script that is provided below. Screenshots below capture what the MAT file will look like loaded in MATLAB's workspace. 

Not shown above:

Meta.transducerHeight - This is an offset height (m) relative to the instruments' base level, used to account for the varying heights of multi-frequency, separately mounted tranducers. By ONC convention the site depth is the depth the instrument platform floor, while the siteDevice offset is the depth change from the platform to the instrument, but in this case that offset will be measured to the transducer mounting base.

Data: structure containing the AWCP data, having the following fields.

Config: structure containing instrument configuration details. For details about the configuration parameters, refer to the manufacturer documentation. This structure contains a conglomeration of parameters from all 3 types. All parameters are the original instrument settings as read from the raw data except otherwise noted (in particular, Calibration, speedOfSpeed, orientation and ProcessingOptions are applied in postprocessing to calibrate the data)

These values may not be read from the raw data:


Units: structure containing unit of measure for fields in structures above. For instance, units.frequency='kHz'. Note that channel specfic data units: profileData, rangeToBinCentre are stored in

Oceans 2.0 API filter: extension=mat

ASL Profiler Time Series MAT file Conversion Script

This script will convert MAT files to the VENUS ZAP MAT file format. It works on data loaded in the workspace and is intended to be used as basis for users to adapt their code and analysis to the new format, which will be the standard format into the future. Download the script file and open in matlab, press the 'run' button, the script will open a window to select an ASL Profiler MAT file to process, after loading the ASL Profiler MAT file, the workspace will be populated with the familar ZAP MAT file structures: zapdata, config, units, meta, while the ASL MAT file structures will remain (ASL MAT file structures follow the MATLAB convention of naming structures with upper case letters).

ASL export CSV files

In the ASL software (AZFPLink in the case of AZFPs), there is an option to export a CSV data file of the Volume Backscatter and/or Target Strength profiles. This data product replicates that export. The resulting files contain the same data as the above MAT file product., conforming to the export format that is compatible with EchoView's import. If users export with the calibrated option on, they can view the data directly in EchoView without the need for further information. AZFPLink does also export a binary representation of this file with the header and ancillary information in a CSV file and the backscatter in a simple binary file named with the extension .bin. This .bin format is not available. We find that the full CSV file is the same size when compressed and works just as well.

Here is an example of the CSV files, one file for each of the backscatter or target strength, pitch and roll:





The file-name modifiers are any ensemble averaging, the echosounder channel centre frequency and data type: pitch,roll, sv (Volume Backscatter), ts (Target Strength), raw (uncalibrated). 

ASL .01a raw binary data files

.01a files are the echosounder's binary raw internal data that is stored on the Compact Flash drive. In the normal raw file acquisition process for ASL echosounders, users usually copy the files directly off of the Compact FLASH drive. This format is compatible with a number of data analysis and visualization software, particularly EchoView (version 7.1 and later of EchoView will read .01a files). This is the default data product option. An alternate format, with the same file extension (.01a) is also available, denoted as Unaltered Serial Stream data. This is the data that ONC device drivers record in real-time: Big-Endian with packet headers, as if one were recording the RS232 communications directly. The is the "Real Time Profile Output Format" documented in Section 8.1 of the AZFP software manual. Compared to the Serial Stream, the Compact FLASH format is also Big-Endian, but the packet headers are replaced with a FLAG value, so that the file is FLAG-profile-FLAG-profile, etc, refer to Section 8.3 of the AZFP software manual for the Compact FLASH format. Another format that is not offered at this time is called 'Real Time Data Files' (section 8.4 in the manual): these are .001 files acquired via the ASL software (via RS232 serial communications), but with packet headers replaced with a different FLAG and converted to Little-Endian; this source could be added at a future date, upon request. The three variations also are documented in the AWCP user manual (posted at the top of this page), while the ZAP manual only documents the Serial Stream format (Appendix F in that manual). 

The .01a files for AZFP and AWCP produced by the Compact FLASH option are readable by ASL's software (AZFPLink and their own MATLAB code) and a growing number of 3rd party software and code. See ASL's processing page for more information. .01a files for ZAP echosounders produced by the Compact FLASH option are not likely to be readable however. Refer to Appendix F in WCP manual UVIC Venus version CM-100-WCP-01-R01.pdf - the profiles is taken from byte 27 (the ping interval) onward, excluding the last two byte (line feed, carriage return). Returning the entire packet with the Serial Stream option is likely to be the more usable option.

ONC's normal raw log files record all communication and data with the device in an ASCII hexadecimal format. This data product converts that hexidecimal data to binary, omitting driver commands and ASCII serial responses. The Serial Stream option is that direct output, whereas the Compact FLASH option has the addition trimming and insertions as noted. Live data is available for both options (the log files do not need to be archived for this data product to be available). Files are broken on the hour, every hour, with additional file breaks on driver restarts and configuration changes. On these configuration change breaks, the last letter in the file extension is incremented: .01a → .01b → .01c.

Accompanying these files will be .xml configuration metadata files, which are produced with the start of the data and for every configuration change. The format of the XML files is taken from the a recent ASL XML file, produced by AZFPLink version 1.0.30. AWCPs and earlier AZFPs generated a different XML file, while ZAP echosounders had a .cfg file (very similar to an XML file). The .xml file produced for all three echosounders is the AZFPLink version 1.0.30 format, with a few ONC comments to make it clear it wasn't produced by AZFPLink. The differences between all three are largely superficial - the XML tags for the calibration parameters are the same between the AZFP and AWCP echosounders, while the ZAP uses a formula and parameter set for calibration (see the calibration formulas detailed above). Here is an example ONC produced ASL .xml file: ASLAZFP55036_20140911T060000.742Z.xml (Newer versions of this file have a dateTo in the file-name).

A readMe text file accompanies the Compact FLASH format .01a files that aimed at helping EchoView load the data into EchoView, here is the content of that file (with added illustrations):

Dear Ocean Networks Canada data user,

This file contains additional instructions for users who wish to load and process our ASL manufacturer's binary format .01a files in EchoView.
All data products have extensive documentation. In this case, please refer to: (The section on .01a files is near the bottom of the page.)
We have learned of a few issues that EchoView users may encounter. (Thanks to our awesome users for their feedback.) These issues are:

* Confusion with the Data Search ISO-19115 metadata XML file. If the metadata XML file is in the same directory as the configuration XML files,
EchoView may attempt to load the metadata XML file, which of course contains no configuration information. Loading will succeed but users will
only see a default configuration in EchoView. How to fix: delete any files with names ending in META.xml from the directory containing the .01a files,
delete/clear EchoView to start over, import the .01a files again. How to avoid: when downloading data products from Data Search, users can skip
downloading the META.xml files by clicking on the data product link for each search, instead of the red download button that downloads all
products in a search cart, including the META.xml files. (We do recommend that users keep the META.xml files for reference, perhaps in
a separate directory.)

* EchoView may load the wrong configuration XML file if there are multiple configuration XML files in the directory where the user is loading
.01a files from. How to fix: check the directory where the data products have been unzipped after downloading. If there are multiple configuration
XML files, move each into separate directories. For each configuration, match the .01a files with the configuration XML files based on the time in
their filenames and move the .01a files to the directory with their corresponding configuration XML files.

* EchoView doesn't appear to reload XML files when new files are imported to an existing configuration. How to fix: always start with a
new project, load files grouped by their configuration as noted above.

* An alternative method is also offered: in Data Search, the CSV option under "ASL Acoustic Profiler Time Series" provides data files reproducing
the ASL software (AZFPLink) CSV export. These CSV files are calibrated (see the accompanying data product options) and are readily loaded into
EchoView. The disadvantages of this method include the lack of metadata that EchoView may need to perform other analysis, and that the file sizes
are quite large.

* EchoView has capabilities to manually input and edit configuration values, see their extensive and very useful help pages for this information.

* If all else fails, contact us: and/or contact EchoView customer support.


- ONC Data Products and Data teams

We seek feedback on this data product. It is difficult to test and evaluate. Hopefully it is compatible with your software and uses. Please contact us if you need any support or would like to suggest changes.

Plots: PNG and PDF

There are two formats of plots available: PNG or PDF. A PDF plot file can contain multiple plots as separate pages, and the graphics are vector images, which are better for printing or viewing at high resolution.  The PNG format is a single plot in a raster image which is good for quick viewing and sharing. The data and appearance of the two plot formats are the same. These plots are also known as echograms, they plot echo intensity (backscatter or target strength) vs time and depth, and are basically what you would see as a sonar operator. The calibration data product option switches the values plotted between raw (uncalibrated), Volume Backscatter (Sv) and Target Strength (TS), but does not otherwise affect the form and function of the plots. The plots are affected by the ensemble/averaging option, the number of channels, the deployment type (fixed vs. mobile) and the sun elevation data product option.

Oceans 2.0 API filter: extension={png,pdf}

Plots: Daily vs Multi-day plots

There are two variations of plots in terms of duration, depending on the ensemble period option selected. Daily plots are generated with the default, no averaging, option. Daily plots will show a maximum of one day of data. For all plots, the data has to be resampled so that each pixel in the PNG is an ensemble period, otherwise rendering the image will alias the data; so in spite of selecting the no-averaging option, some resampling may happen. This resampling is important as normal resizing on computer screens appliles linear image anti-aliasing routines which are not appropriate for logarithmic scale images. The minimum ensemble period for a one day plot is ~30 seconds. If you select less than one day, you can effectively zoom in and see higher temporal resolution. Here are some examples of daily plots: first is a ZAP calibrated daily echogram with the sun elevation plot; second is a ZAP daily echogram, non-calibrated without the sun elevation plot, with a configuration change part way through the day; third is an AZFP calibration daily echogram without the sun elevation plot.

If an ensemble period is selected by the user, the plots will be multi-day plots and only one plot will be generated over the search time range (excluding configuration changes, which break the plot). Ensemble averaging will be applied as selected, except when the selected ensemble period is not high enough to prevent aliasing and distortion, the ensemble period will be increased automatically. Below are examples of multi-day plots from a ZAP and an AZFP with ensemble averaging set to 10-minutes, which is easily long enough to avoid aliasing and distortion. If plots extend over gaps in the data, users will see the gaps represented by white space.

Plots: Single vs. Multiple Channels

If the echosounder has multiple channels, as in the examples above, each channel will be plotted as a subplot, with independent axis and limits. (Axis limits are set from fixed intervals, e.g. every 20 dB, to facilitate inter-plot comparison.) In addition, if the device has precisely 3 channels, an additional RGB composite plot will be shown. For this subplot, each channel's data scaled from 0 to 1, each channel is then represented by a primary colour, and the colours are combined to form an image. In this way, users can see composite details: various targets will appear as different colours, depending on their relative target strength as a function of frequency. This is useful for differentiating the targets between fish, zooplankton, bubbles, whales, etc.

Plots: Mobile Depth

Here is an example of single channel plot, from a mobile AWCP echosounder on the vertical profile system where the y axis is not depth, but is instead echosounder range. We can't use depth as it is varying throughout the data. Future improvements maybe to register the pings with the varying depth, so that the y axis can be depth. 


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