Kongsberg echosounders data files

Echoview supports data files from the following Kongsberg echosounders:

Notes:

EM 710 data files (.all)

These files contain multibeam data logged from an EM 710 echosounder. Data is represented in Echoview on multibeam echograms.

These files contain a series of datagrams. Only the Water column, Position and Heading datagrams are read. All other datagrams are ignored.

The Kongsberg EM 710 echosounder can have up to 512 beams. In all other respects, the data read from EM 710 (.all) files is treated in the same way as EM 3002 (.all) data files.

EM 3002 data files (.all)

These files contain multibeam data logged from an EM 3002 echosounder. Data is represented in Echoview on multibeam echograms.

These files contain a series of datagrams. Only the Water column, Position and Heading datagrams are read. All other datagrams are ignored.

The Water column datagram records a single ping, and is interpreted as follows:

Range

The minimum range of a ping is assumed to be 0 meters.

The maximum range for any beam is calculated as:

Maximum Range = Sample Thickness x (Start Range Sample Number + Maximum Number of Samples) x 0.5

Where:

Sample Thickness = Sound Speed / Sampling Frequency (m)
Sound Speed is read from the Water column datagram (m/s)
Sampling Frequency is read from the Water column datagram (Hz)
Start Range Sample Number is read from the Water column datagram (one value per beam)
Maximum Number of Samples is read from the Water column datagram (one value per beam)

The maximum range of a ping is the largest of the maximum ranges for all beams in that ping.

Note: The EM 3002 format supports different ranges for each beam, Echoview supports a uniform range for all beams only. Beams shorter than the longest beam are padded with no data samples by Echoview.

Amplitudes

The raw variable "unspecified dB pings " contains the sample amplitudes calculated as follows:

Amplitude = Stored Value * 0.5 (dB)

Where:

Stored Value is an integer from -128 to 127 as read from the Water column datagram.

Note: Amplitudes may therefore range from -64 to 63.5 dB. The reference is currently unknown.

Sv

The raw variable "Sv pings" contains Sv data derived from the amplitudes of the unspecified dB variable as described in Multibeam Magnitudes to Sv. Please note that unspecified dB amplitudes of -64dB are interpreted as below threshold data (-999dB) in the derived Sv variable.

The value of TVG embedded in the recorded data is specified by the TVG function applied field in the Water Column datagram.

Beam geometry

Individual beams may have different beam widths and ranges. Echoview supports varying beam widths in multibeam data, but currently supports only a constant range for all beams. As a consequence, echograms of EM 3002 data are filled to the maximum range with no data. That is, in Echoview all beams are of equal range and samples which are not available in the Water column datagram are given the value "no data". These samples are typically displayed in the background color, but they are there and will appear in exports and influence the display of echograms.

The beam angles read from .all files are negated (multiplied by -1) in Echoview to ensure that the EM 3002 multibeam echogram display conforms with Echoview norms: Beam 1 being on the far left with a negative beam angle.

Format version

Echoview supports two distinct versions of the .all file format. A significant change to the format was introduced on December 17th 2004. Echoview distinguishes between them on the basis of the TVG function applied field in the Water Column datagram. Old format files have 0 for this value (this space in the datagram was occupied by two spare bytes in the old format), and new format files contain a number from 20 to 40. The obtained TVG function applied value is used in the calculation of Sv, meaning that old format files will use a TVG correction of 0.

Note: Echocheck will report which format (new or old) is detected.

EM 3002D data files (.all, .wcd)

The *.all files contain multibeam data logged from an EM 3002 echosounder with a dual head (D). Data is represented in Echoview on multibeam echograms. Separate variables are derived from data associated with the second head. In all other respects data is treated as for EM 3002 data files.

The *.wcd file format containing water column data may also be read by Echoview. The *.wcd files are treated in the same way as *.all files. Please note, complete support for the *.wcd format is unavailable in this release.

MS 1000 data files (.smb/.nnn)

The MS 1000 scanning sonar uses a single beam which scans by varying the tilt and bearing of the beam. The resulting data is represented in Echoview by one H-mode ping with no data samples on all beams except the single beam recorded.

You can use the beam scan operator to generate H-mode pings with more than one beam containing data.

Echoview supports 8-bit or 4-bit (compressed) sample data in MS 1000 data files. The 4-bit data is uncompressed using an algorithm provided by Kongsberg.

Note: Prior to Echoview 4.60, 4-bit sample data was not supported. 4-bit sample data was incorrectly read by Echoview and problems with such files only appeared when you scrolled to the end of the echogram.

Geometry

Echoview reads from the EXTRA_HIGH_FREQ_SONAR_TUPLE_DATA header the values of StepSize and StartAngle.

StepSize is used to calculate the number of H-mode beams used to represent the ping:

Number of beams = 360 / (StepSize x 0.225)

where StepSize is in 0.225ths of a degree.

StartAngle is used to calculate the number of the beam in this H-mode ping which is populated with data:

Beam number = StartAngle x 0.225 x Number of Beams / 360

where StartAngle is in 0.225ths of a degree and beam number 0 is taken to be in the direction of travel (for a moving platform) or north (for a fixed platform).

Echoview reads from the DATA_TYPE_SETTINGS tuple the value of TiltSectorHeading, which is used to calculate the tile angle as follows:

Tilt angle = TiltSectorHeading x 0.225

Where TiltSectorHeading is in 0.225ths of a degree.

Range

Echoview reads from the EXTRA_HIGH_FREQ_SONAR_TUPLE_DATA header the values of SamplingRate and SamplingDelay and from the DATA_TYPE_SETTINGS tuple the value of SampCount.

SamplingRate is used to calculate the sample thickness as follows:

Sample thickness = Sound speed / SamplingRate / 2

where Sound speed is taken to be 1500 m/s and SamplingRate is in Hertz.

SamplingDelay is used to calculate the start range as follows:

Start range = SamplingDelay * Sample thickness

SampCount is used to calculate the stop range as follows:

Stop range = Start Range + SampCount x Sample thickness

Magnitude

The magnitudes are read for the DATA_TYPE_SONAR tuple and stored as single number from 0 to 255 representing the received signal strength with a time varied gain applied.

Sv

The received power is calculated for Sv calculations as follows:

Πr = 20log(Magnitude)

where Magnitude is the number form 0 to 255 read from the data file Πr is in dB and used in the Sv equation.

Echoview reads from the DATA_TYPE_SETTINGS tuple the value of TvgAFactor for use in calculating Sv. It is typically 20, 30 or 40.

SM20 data files (.smb/.nnn)

The Kongsberg SM20 system consists of a Simrad SM2000 multibeam echosounder and an SM20 specific processing PC and software. In Echoview, there may be some small differences between SM20 and SM2000 data files:

Beamformed and unbeamformed data are represented in Echoview as multibeam echograms.

M3 data files (.imb/.nnn)

The Kongsberg M3 is a multimode multibeam imaging sonar that outputs high resolution data. *.imb files contain beamformed data logged by the M3 sonar. The file format includes ping, pitch, roll, (ping)heading and GPS data. Kongsberg M3 file handling manages M3 data in file sizes of 1GB. The first file's extension is .imb. Subsequent file extensions are numbered i.e. .001, .002, .003 etc.

The M3 sonar head orientation may be specified with settings on the Orientation page of the Transducer Properties dialog box. Kongsberg M3 Mounting field data is not used by Echoview however the Mounting field value may record M3 sonar head orientation. Refer to the instrument's installation manual for more information.

Magnitude is derived from the beamformed sonar data (stored in complex format) read from the data file. Magnitude is exported as underlying data.

Unspecified dB = 10*log10(magnitude)

Sv is calculated by the Magnitudes to Sv algorithm, using the unspecified dB value, with proprietary TVG removed.

Ranges are calculated with a proprietary algorithm that is specific to the M3 file format version.

The date and time are calculated with respect the LocalTimeOffset that is read from the file.

Notes:

Flexview data (.imb)

Echoview reads Kongsberg Flexview multibeam sonar *.mmb data that has been converted and saved to the *.imb file format. Data handling and display follows the support for the Kongsberg M3 *.imb data file format.

EA640 data files (.raw)

The Kongsberg EA640 is a high performance wideband single beam echosounder developed for hydrographic use in deep to medium waters. Kongsberg EA640 *.raw data is handled the same way as Simrad EK80 data.

Echoview uses EK80 Power to Sv and Power to TS equations for Kongsberg EA640 *.raw data.

See also

Raw variables derived from Kongsberg data files
Calibration settings for EM 3002 data
Calibration settings for EM 3002D data
Calibration settings for MS 1000 data
Calibration settings for SM20 data
Calibration settings for M3 data
Calibration settings for EK80 raw data
Multibeam display note