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Open-File Report 02-045, Chirp Subbottom Data, Northeastern Gulf of Mexico, Disc 1

Title Page - Introduction - Cruise Report - Equipment - Chirp Data - Shotpoint Maps - Navigation - Pictures - Metadata


Data Acquisition Equipment

Sidescan-Sonar and
Chirp Subbottom Towfish:

Sidescan-sonar chirp subbottom towfish

Datasonics model SIS-1000

Data Collection Platform:

Trition Elics International ISIS

Triton Elics International ISISTM

Specifications for the Subbottom profiler portion of the SIS-1000:
(for more information, see Benthos, Inc. (
Transducer: Transmit projector array; line array receiving hydrophone; 30º conical radiation pattern
Frequency: 2kHz to 7kHz swept FM (4 KW output), synchronous with sidescan
Resolution: 10 cm
Processing: Calibrated transmit waveform stored in ROM, matched filter FFT digital signal processing
Scale Selection: 25 meters to 750 meters full scale

Tow Vehicle Specifications:
Depth Rating: 1000 meters
Vehicle Dimensions: 18 inches OD x 64 inches long
Weight: in air: 300lbs; in water: 170 lbs
Specifications for the ISISTM Acquisition System:
(for more information, see Triton Elics International
red bullet Windows 95 based Pentium machine
red bullet Saves sidescan-sonar data via network interface or on an Exabyte 8200 tape subsystem
red bulletWill accept up to 5 channels of data
red bulletSerial I/O ports (i.e., for navigation)
red bulletParallel (Centronics) ports for printing the sidescan-sonar data
red bulletArray processor handling the digitized sidescan-sonar signal
red bullet12 bit analog to digital converter OR: DSP card for digital signals
The topside data acquisition computer the USGS uses to collect and store the digital signal is the ISISTM> system, which runs under the Windows 95 operating system and is built by Triton Elics International, Inc. (, Watsonville, CA using a 12-bit (72 db effective dynamic range) A/D converter in conjunction with an array processor. ISISTM is capable of digitizing up to four channels of information at aggregate rates of up to 750 kHz, thus preserving the content and the dynamic range of the sidescan-sonar signal. An installed Digital Signal Processing (DSP) board is an alternative to handling signals digitized at the towfish (SIS-1000). Port and starboard sidescan-sonar data are displayed in real-time on a high-resolution color display (1280 x 1024 pixels). Telemetry from navigation systems and the towfish, including full towfish attitude information, is displayed in separate windows. The backup data storage media used is 8 mm Exabyte tape.

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Title Page - Introduction - Cruise Report - Equipment - Chirp Data - Shotpoint Maps - Navigation - Pictures - Metadata