WASSP data files

WASSP multibeam sonars (including WMB-3250 and generation 3 systems) write numbered data files. WASSP software can convert these to *.nwsf files which can be read by Echoview. WASSP *.nwsf files have a proprietary file format. For further information about WASSP sonars or the *.nwsf file format refer to the WASSP website.

Echoview reads the:

Raw Output Data packet (output by sonar)
Uncorrected Bathymetry packet (date and sound speed)
External Sensor Data packet (GPS and other position data)
Raw Water Column Data packet
Navigation Data packet (GPS fixes, heading, roll, pitch and heave data)

Data start range is zero.

Data stop range = SoundSpeed * SamplesPerBeam * 0.5 / SamplingFrequency

Where:

SoundSpeed (m/s) is read from the data file and is displayed as SoundSpeed (m/s) on the Calibration page of the Variable Properties dialog box.

SamplesPerBeam is read from the data file.

SamplingFrequency (Hz) is read from the data file and is displayed as SamplingFrequency (kHz) on the Calibration page of the Variable Properties dialog box.

During WASSP system start up, the Transmit Mode Button passes through a self-calibration state1. As a result, pings written to the data file can be "Uncalibrated" or "Calibrated" and this is displayed as Device calibrated (true or false) in the Details dialog box Ping (from file) section. Pings with "Device calibrated: false" may appear blank and require adjustment of the color scheme and/or the display threshold to make them visible. WASSP self-calibration and Echoview calibration are unrelated.

Pings in the data file have a sequence number, which is displayed under Datafile Ping Number in the Details dialog box Ping (from file) section. Missing sequence numbers are flagged with a message on the Message dialog box.

External sensor data packet variables may add the NMEA string name to the variable name.

Navigation packets have no time stamp but are assigned the time stamp of the preceeding ping. As a result, navigation packets that occur before the first ping are ignored. Where multiple navigation packets occur between two pings, only the data from the first packet is read.

Notes:

*.nwsf data files may contain a different number of beams than the nominal beam count associated with the recorded product type.
Echoview assumes that the value for absorption coefficient recorded in the data file has units of dB/km.
Echoview ignores pings that are out of time order or pings where data is unable to be read.
WASSP files can be verified by Echocheck.

Footnote: 1. WASSP WMB Operator manual: Transmit Mode Button

WASSP data files

See also