TOWFISH DRIVERTOWFISH DRIVER

TowfishTowfish The towfish is used to localized à towed sensor without USBL posit, The towfish is used to localized à towed sensor without USBL posit,

sidescan sonar, magnetometer…..sidescan sonar, magnetometer…..

The towfish driver allows an accuracy estimated position of the The towfish driver allows an accuracy estimated position of the mobile by merging different information and filtering navigation of mobile by merging different information and filtering navigation of the boat.the boat.

In a hardware configuration several mobile could be create, a In a hardware configuration several mobile could be create, a Towfish driver could be associate to each mobile.Towfish driver could be associate to each mobile.

If two mobiles are created, the sidescan sonar mobile should be the If two mobiles are created, the sidescan sonar mobile should be the first in the configuration, the shared memory root the first mobile first in the configuration, the shared memory root the first mobile position to the Sidescan survey program.position to the Sidescan survey program.

Depth

Altitude

Depth Boat

A-Frame Offset

Z Offset

Towfish driver setting Sidescan Survey Information Survey Information Towfish Driver Calculation

Cable out x Catenary factor

Layback Calculated

Towfish: Merge InformationTowfish: Merge InformationHorizontal distance

Towfish: Filter and smooth Boat navigationTowfish: Filter and smooth Boat navigation

In real time the driver makes a calculation of the mobile position by applying filter and latency on the boat heading.

The estimated calculation of the mobile is close the reality.

Setting up a Towfish DriverSetting up a Towfish Driver In Hardware, add the In Hardware, add the

driver to position your driver to position your main vessel main vessel GPS.DLL in this example.GPS.DLL in this example.

Create a 2 mobile for your Create a 2 mobile for your towfish position.towfish position. Named ‘Sidescan’ in this Named ‘Sidescan’ in this

example.example. Select a driver to position Select a driver to position

the towfish.the towfish. Towfish.DLLTowfish.DLL

Select Sidescan Survey in Select Sidescan Survey in System (check Include box System (check Include box for Sidescan Survey)for Sidescan Survey)

NoteNote::If you are towing a sidescan, you need to create the mobile in If you are towing a sidescan, you need to create the mobile in Hardware before selecting the sidescan optionHardware before selecting the sidescan option

Configuration SampleConfiguration Sample

Configuration with a sidescan sonar and Magnetometer.Configuration with a sidescan sonar and Magnetometer.

Connection Block Diagram With SSConnection Block Diagram With SS

Towfish driver calculated in Real Time the position of the mobile.

Information is passed between the two modules using the shared memory.

HYPACKHYPACKSURVEYSURVEY

SIDE SCANSIDE SCANSURVEYSURVEY

GPS Side Scan Sonar

POSITION, HEADING

MEMORYSHARED

Sensor AltitudeDepth value

Your computerYour computer

Mobile position Hypack Mobile

Pulley

Set upSet upCable out input source

Layback Method calculation

Number of segment

Pulley’s Offset in Boat referential.

Record method if connection with the pulley is lost

Catenary factor value ie

K=0.9 pour 100m cable out the cable out value calculated is 90m.

Depth Source if advanced formula is used for calculation.

If Depth Source= Fish Depth use to select the Depth value:

-Shallow fish: fish at the surface

-Deep fish: deep under the boat

-Depth Sensor/Altitude Sensor coming from the selected channel

Set upSet up

DO NOT USE GENERIC OFFSET.DO NOT USE GENERIC OFFSET.

Layback method calculation: HYPACKLayback method calculation: HYPACK

Layback method calculation T. BackerLayback method calculation T. Backer

Layback method calculation: SHOMLayback method calculation: SHOM

Layback method calculation : SHOMLayback method calculation : SHOMBasic Method :

Do not apply Pythagoras Calculation only the multiplication of the catenary factor and the cable out.

The result will be the Layback.

Layback method calculation : SHOMLayback method calculation : SHOMClassic Method.

Pythagoras with values coming from.

Hardware:

•Catenary factor,

•Z pulley.

Survey

•Cable Out.

Sidescan Survey

•Sensor immersion•Boat Depth –Altitude or Depth sensor

For a good calculation: For a good calculation: •Zero pressure sensor should be done on subsurface.Zero pressure sensor should be done on subsurface.•Zero Pulley should be done at the pulley.Zero Pulley should be done at the pulley.•If (I+z)²>(k.L) then an alarm is displayed in real time.If (I+z)²>(k.L) then an alarm is displayed in real time.

Layback method calculation: SHOMLayback method calculation: SHOMSpecific Method is equivalent to Classic Method.

This method is more adapted:

•when the pulley Z offset is important.

•When the surveyor want to do the zero pulley at the surface.

For a good calculation: For a good calculation: •Zero pressure sensor should be done on subsurface.Zero pressure sensor should be done on subsurface.•Zero Pulley should be done on subsurface.Zero Pulley should be done on subsurface.•If (I+z)²>(k.L) then an alarm is displayed in real time.If (I+z)²>(k.L) then an alarm is displayed in real time.

If (I+z)²>(k.L) then an alarm is displayed in real time.If (I+z)²>(k.L) then an alarm is displayed in real time.

Layback method calculation: SHOMLayback method calculation: SHOM

Cable out input MethodCable out input Method

Several counting pulley could provide automatically the cable out information via a serial connection or shared memory.

The towfish’s immersion for Sidescan.The towfish’s immersion for Sidescan.

Two possibilities:

1.Depth sensor on fish, then select Sidescan interface and Depth Sensor.

2.There is no Depth Sensor on the sidescan then the immersion is approximate calculation.

SS Depth=Boat Depth- SS Altitude

TThe towfish’s immersion for other sensorhe towfish’s immersion for other sensor

Some towed sensor as Magnetometer could provide depth information.

Depth Source:•Enable Mobile Depth

Fish Depth•Enable Depth Sensor

Fish Depth Channel•Select the input Channel

Towfish Survey WindowTowfish Survey Window

Display Tab

Display all the different information

Cable Out and altitude graph

Towfish Survey WindowTowfish Survey Window

Visual Graph

Towfish Survey WindowTowfish Survey Window

Variables Display

Towfish Survey WindowTowfish Survey Window

Cable out Manual Input

In Manual Mode, cable out could be set by:•Using arrow•Input in the dialog box

The Cable out Adjustment:

If a counting pulley is using the cable could slide on the sheave, if cable mark has been done then surveyor could adjust the cable out value.

How improve the estimated position

1-mark you cable (10m,15m,20m..) to control the information delivered by the pulley.

2-when you put back the fish on boat check the coherence of the zero pulley you did when you put the towfisn in the water.

3-If it is a long survey it could interesting during the day to do again the zero pulley.

These actions will improve the estimated position of the fish, note that a transvers current could decrease the position.

Calculated the Catenary Factor for SS

1-Do the same line in the two ways on a remarquable obstruction.

2-In Hyscan make a target on these obstructions for each line

3-Measure the distance between the two targets divide per 2 or the average of the distance between the obstruction and the target,

It is the Error E

4-In Hyscan load the two lines and activate spredsheet

5-Clic on the obstruction the spreadsheet will display the value

Calculated the Catenary Factor for SS

6- Take the information in the spreadsheet.

• Layback Logged is the calculation did by towfish driver

• Cable out (L)

• Depth: sensor immersion (I)

• Pulley Offset (Z) from Hardware

7- Calculate the correct K factor.

Calculated the Catenary Factor for SS

The K factor depends of the survey speed and the cable out value.The K factor depends of the survey speed and the cable out value.

For the same system the k value could be different for 20 m cable out and 150m cable out.For the same system the k value could be different for 20 m cable out and 150m cable out.