Seabed Classification

Category:

Geotechnical Evaluation Methods

Surveying

Description:

QTC VIEW processes information from echosounders to classify seabed based on backscatter

analysis from acoustic signals. The QTC VIEW classifies the seabed by first describing the

echo and then comparing that description to calibration data from known seabed types. The

system consists of a signal processor fed from the customer's echo sounder.

The processor analyzes the signals and compares them to a template. The system accomplishes

this by digitizing the first return from the echo sounder, then characterizing its shape and

identifying the three most statistically important features of the waveform. The template

contains signals for echo sounders working on known bottom conditions, typically provided by

the customer. The result is a set of three values representing each echo. Requires calibration

using seabed of known classification, then comparing calibration spectrum with that of

unclassified seabed. Output from processor is converted to a PC. Output format is in text file

format.

The operation involves two phases: calibration and survey operation. During calibration the user

would go to a known seabed and collect a set of echoes. This normally requires about 10

minutes at each station. Data are then processed to form a catalog representing each calibration

site as a seabed class. In survey mode, the user invokes a catalog, and as the echoes along the

track are received the system chooses the class whose calibration data are most similar to the

incoming echo and displays it on the computer screen. The system also estimates confidence in

that choice. Calibration data are stored as individual data files, allowing the user to develop a

library of seabed types that can be used to create catalogues for specific applications.

Common applications for QTC VIEW include fisheries habitat and other environmental studies,

dredging and mining.The system has been used on beach renourishment projects to delineate

areas of previous dredging on an area of seabed with minimal relief.

QTC VIEW system used by American dredge contractor (Great Lakes Dredge & Dock) for

Navy predredge surveys, and by the Dutch in Ijmuiden, Holland.

Equipment is commercially available and in use in 17 countries.

Reviewer:

C. Woolley

Company / Organization(s):

Access Restricted to U.S. Army Corps of Engineers

Information Sources:

Literature:

September

Month:

1996

Year:

Periodical

LitType:

IDR

Publisher:

Page:

Interviews:

Karl Rhynus

Interviewee:

John Lally

Interviewer:

9/1/98

Interview Date:

Telcon

Interview Location:

Chapter 5 Other Technologies Reviewed