Newsgroup: it.hobby.scuba
Titolo: sonar on Ebay

Side Scan Sonar Edge Tech EG&G 272T /   wreck hunting
On ebay:
http://cgi.ebay.fr/ws/eBayISAPI.dll?ViewItem&rd=1&item=170148760929&ssPageName=STRK:MESE:IT&ih=007
SONAR A BALAYAGE LATERAL
Side Scan SONAR Edge Tech EG&G 272T towfish, 100 Khz Perfect state.
The best sonar for wreck and shipwreck research & recovery, treasure 
hunting, wreck hunting.
This Side Scan Sonar been used for a long time but completely refited 
and repainted with EG&G logos.
Tested recently in shallow water, working well.
Two pairs of wings, nice wooden white box, 55kg .
More informations, sonar imageries, shipwrecks and mosaiks on 
www.ceresm.com
Feel free to contact directly 
www.ceresm.com
 for further informations
272-T Tow Fish
Frequency 100 kHz - 105 ± 10 kHz
Horizontal Beam Width 100 kHz – 1.2° (3 dB points)
Operating Range (maximum) 100 kHz – 500 meter swath
Optimum Operating Depth 1000 meters
Tow Cable Type 7 conductor
Tow Fish Diameter 11.4 cm (4.5”)
Tow Fish Length 140 cm (55”)
Towing Speed (operational) 3 – 5 knots
Weight (in air) 25 kg (55 lbs)
Weight (in saltwater) 12 kg (26 lbs)
Provide High Resolution Seafloor Images
     The Model 272 towfish is a hydro dynamically stable, towed body 
that contains the electronics and transducers necessary to generate and 
receive side scan sonar signals. It is designed for use at depths up to 
1000 meters. Various tow cable systems provide the mechanical means for 
towing the fish near the seafloor and the electrical means for powering 
the fish, triggering the transmitters, and sending the return signal to 
the topside for processing and display.
     The Model 272-T towfish incorporates circuits for transmitting and 
receiving the 100 kHz side scan sonar frequency.
      The Model 272-T  towfish feature the patented Saf-T-Link® shear 
pin feature. When cable tension on the towfish exceeds 180 Kg (400 lbs.) 
due to snagging on the seafloor or mooring lines, the nylon pin shears 
and the electrical connector between the cable and tow fish separates. 
The towfish then "flips" 360 degrees, transferring the tow point to the 
nose of the towfish and allowing it to be pulled clear of the 
obstruction. Normal operation is easily restored by remounting the 
towing arm with a new shear pin and refastening the connector. If only 
the tail fins snag, they will fall away and be loosely held by a nylon 
cord. The cord is designed to break if the snag persists to avoid loss 
of the towfish.
     272-T  features a patented Time Varied Gain (TVG) circuit that 
compensates for the known signal losses versus range. This not only 
facilitates processing, but also reduces the dynamic range requirements 
of the tow cable, thus reducing the susceptibility to electrical nose 
pickup.
     272-T  can be towed with lightweight Kevlar tow cable or, for 
deeper waters, by double armored steel-cables.
FEATURES
operates at 100 kHz, Time varied Gain, Saf-T-Link towing arm, Breakaway 
tail fins, Lightweight for one-person deployment/recovery, Corrosion 
resistant
Rugged, modular construction for ease of maintenance
APPLICATIONS
Shipwrecks research & recovery / Hydrographic surveys / Channel 
conditioning and clearance surveys / Geological surveys / Cable and 
pipeline surveys / Search and Recovery / Site selection surveys / 
pre/post dredging surveys / Mine countermeasures / Treasure hunting
I. SEAFLOOR SEARCH
This is the process of detecting and recognizing a seabed anomaly using 
sonar for the purpose of identification, disposal, or retrieval. 
Detection is a function of sonar design and acoustical physics while 
recognition is highly dependent upon the eye-brain interface and 
operator experience. Typically, small objects on the bottom can be 
partially or completely buried, or, in shallow or deep moored 
configurations. Small objects are detected by the size and shape of the 
acoustic shadow, which is a derivation of the acoustic reflection, fish 
altitude, and grazing angle at which the sound waves strike the object.
Applications for marine search include: Explosive Ordnance Disposal, 
Q-Route Survey, Site Clearance, Search and Recovery of Downed Aircraft 
and Sunken
Shipwrecks.
Mine Countermeasures
The search and disposal of underwater mines requires constant effort on 
the part of militaries worldwide. Shipping channels must be kept open 
and free from mines.
Over the past decade, Sonar data acquisition and image processing system 
has played a critical role in the identification of underwater mines 
worldwide. 272T have been used internationally.
Aircraft Search and Recovery
Edgetech products have aided in the search and recovery of downed 
commercial and military aircraft worldwide.
Search and Recovery of Shipwrecks
Some of the world's most highly publicized shipwrecks have been found 
with 272T
Small object Search and Mining
II. HYDROGRAPHIC SURVEY
This is the mapping of the seafloor topography utilizing various 
sensors, including single and multibeam sonars. Surveys are conducted to 
produce nautical charts for safe navigation or to provide the detailed 
mapping of pipeline and underwater cable routes.
Pier and Harbor Survey
The Sonar data acquistition and image processing system provides 
detailed information on survey depths of harbors by providing real-time 
graphical displays of data. This information allows for safe navigation 
of marine traffic. Isis also offers details of the underwater condition 
of harbor walls to help identify weaknesses and hazards.
Breakwater Survey Breakwaters are built to protect harbors from damaging 
storms. The harsh marine environment often degrades the breakwaters 
leading to unsafe navigation around the area. Locating damaged areas of 
the breakwater before a failure is critical. This can be accomplished 
with 272T Sonar .
Dam/Reservoir Survey
The  Sonar in conjunction with multibeam systems make it possible to map 
intricate stilling basins associated with dams and reservoirs. Surveys 
are conducted to detect hazards caused by erosion, or to provide 
valuable, up-to-date information for the accurate computation of water 
storage volumes.
III. DREDGE WORK
Pre/Post Dredge Survey
Two surveys are usually conducted to support dredging operations; 
Preliminary and Post survey operations. This information allows the 
dredge to determine how much area is required to be removed and to then 
produce a final survey to verify that the depth meets all navigation 
requirements. High accurate survey data is required. The 272T sonar has 
gained international acceptance as one of the most efficient and 
accurate data acquisition and processing system.
Dredge Support
During dredging operations, survey support in the work area allows the 
operator to determine if the correct depth has been achieved. An 
isolated pile or missed area can result in higher costs if the dredge 
must return to the area. The sonar can provides real-time coverage of 
the area, providing very accurate depth measurements for the operator.
IV. SAFETY AND INSPECTION WORK
Bridge abutment Inspection
Every railroad, roadway or bridge over a river is suspect to the 
potential underwater erosion of its supporting piers. (A high current 
area can quickly lead to erosion and possible failure of the structure.) 
Rivers can quickly erode the sediment beneath the support, weakening 
bridge supports and potentially lead to structure failure.
River Flooding Support
Several countries have experienced severe flooding to low lying areas 
because of unusual changes in World climatic conditions. Water levels of 
major rivers have risen and broken their banks.
Rock Dumping
Rock dumping is the accurate placement of rocks onto the seafloor to 
achieve a specific objective. Typically rocks are placed over an exposed 
pipeline laying on the seafloor. Time and materials are saved if the 
placement is exact.
Pipeline Inspection
Underwater pipelines require periodic inspections and maintenance to 
reduce risk. The inspections determine if they have become exposed, or 
if any erosion beneath the pipeline may have created excessively long 
spans, making it vulnerable to rupturing. The  Sonar Pipeline Inspection 
System tracks up to four pipelines simultaneously, generates on-screen 
tags, reports in real-time and automatically detects free spans, scour, 
burial and other anomalies.

 
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