We often get questions from users who are configuring their hardware and are getting lost in the maze of variables to consider in determining the origin, and changing offset signs. The key below is written to help guide you with these questions. Here's how it works.

Choose the first outline level that fits your setup. Now, under that heading, choose the second level heading that describes your setup. Continue progressing down through the headings until a setup table follows your last choice.
The setup table tells you what to use for the origin, which Hardware program each device should be entered in, and the signs used for the offset measurements.

Note: In all setups, except for the GPS, latency is usually zero. You may enter a value initially from the GPS manual or start with it at zero, but you should run a Patch Test and adjust this setting accordingly. Sonar systems usually automatically compensate for latency. Latency is not an issue for MRUs and Gyros.

I. Single Vessel

A. Gyro for heading

 

1. Single Beam

 

Consideration	Solution
Origin	Transducer
Hardware Setup Program(s)	Hypack Hardware- All devices
Offset Signs & Program(s)	Horizontal offsets are positive forward and starboard Z offsets: Transducer: 0--included in draft correction of device when calibrated GPS: Positive upward

2. Multibeam

There are two possible options for setting up multibeam systems. Solution A maintains the origin always at the vessel's pivot point. Solution B uses the transducer head as the origin in Hypack® Hardware, while Hysweep® Hardware uses the vessel's pivot point. In this case, the helmsman display data is based on the transducer, enabling more accurate positioning of the transducer over the survey line.

 

Note also, in most cases, the rotational offsets of the gyro and MRU are calibrated during installation to the vessel. Any additional error will be compensated for by the Patch Test values that are then applied to the transducer.

 

Consideration	Solution A
Origin	Vessel pivot point - ideal MRU position
Hardware Setup Program(s)	Hypack Hardware-GPS, Hysweep.dll (optional) Hysweep Hardware-MRU, Transducer, Gyro, Hypack.dll
Offset Signs & program(s)	Horizontal offsets: positive forward and starboard of the origin. Z offsets: Transducer: 0--included in draft correction of device when calibrated. GPS: Positive upward from the waterline in Hypack® Hardware; positive downward in Hysweep® Hardware. MRU: For MRUs use zero.** Yaw Offset: Transducer (Determined in Patch Test.): positive for clockwise rotation from alignment with the keel. Gyro*: Usually zero. May add correction for variation between magnetic N and true N. Add the variation to the mounting offset using positive values for clockwise rotation from alignment with the keel. MRU*: positive for clockwise rotation from alignment with the keel. Pitch offset (Determined in Patch Test.): Multibeam sensors not oriented directly below the vessel. Positive forward. Roll offset (Determined in Patch Test.): Multibeam sensors and MRUs* not oriented directly below the vessel. The reference roll angle (in decimal degrees) is 0 for vertical mounting positive to the port side.
Additional settings	If MRU is not at the vessel pivot point, when you edit your data, check Correct for Induced Heave in the Advanced Read Parameters dialog.

Consideration	Solution B
Origin	Hypack Hardware: Transducer Hysweep Hardware: Vessel pivot point-ideal MRU position
Hardware Setup Program(s)	Hypack Hardware-GPS, Hysweep.dll (optional) Hysweep Hardware-Transducer, MRU, Gyro, Hypack.dll
Offset Signs and program(s)	Horizontal offsets: positive forward and starboard of the origin. Z offsets: GPS: Positive upward from the waterline in Hypack® Hardware, positive downward in Hysweep® Hardware. Transducer: 0--included in draft correction of device when calibrated. MRUs use zero**. Yaw Offsets: Transducer (Determined in Patch Test.): positive for clockwise rotation from alignment with the keel. Gyro*: Usually zero. May add correction for variation between magnetic N and true N. Add the variation to the mounting offset using positive values for clockwise rotation from alignment with the keel. MRU*: positive for clockwise rotation from alignment with the keel. Pitch offset: For multibeam sensors (determined in Patch Test.) and MRUs* not oriented directly below the vessel. Values are positive forward. Roll offset: Multibeam sensors (determined in Patch Test) and MRUs* not oriented directly below the vessel. The reference roll angle (in decimal degrees) is 0 for vertical mounting. Values are positive to the port side.
Additional settings	If the MRU is not at the vessel pivot point, when you edit your data, check Correct for Induced Heave in the Advanced Read Parameters dialog of the editor.

 

3. Multiple Transducer 

 

a) System supported in Hypack Hardware.

Consideration	Solution
Origin	Vessel pivot point-ideal MRU position
Hardware Setup Program(s)	Hypack Hardware-all devices
Offset Signs & program(s)	Multitransducer offsets are entered in the Transducer Offsets Program.  Horizontal offsets: positive forward and starboard of the origin. Z offsets: GPS & Transducer: positive upward from the waterline. MRU: Use zero.** Yaw Offset Gyro*: Usually zero. May add correction for variation between magnetic N and true N. Add the variation to the mounting offset using positive values for clockwise rotation from alignment with the keel.

b) System supported in Hysweep Hardware

Consideration	Solution
Origin	Vessel pivot point-ideal MRU position
Hardware Setup Program(s)	Hypack® Hardware: GPS, Hysweep.dll (optional) Hysweep® Hardware: Transducers, Gyro, MRU, Hypack.dll
Offset Signs & program(s)	Hypack® Hardware: Horizontal offsets: positive forward and starboard of the origin. Z offsets: GPS: positive upward from the waterline. Hysweep® Hardware:· Horizontal offsets: positive forward and starboard of the origin. Z offsets: GPS in Hypack.dll is positive downward. Transducer: positive downward from the waterline. MRU: Use zero.** Yaw Offset: Gyro*: Usually zero. May add correction for variation between magnetic N and true N. Add the variation to the mounting offset using positive values for clockwise rotation from alignment with the keel.

 

 

4. Single Beam and Multibeam

 

Consideration	Solution
Origin	Hypack® Hardware: Transducer most important over survey line. Hysweep® Hardware: vessel pivot point
Hardware Setup Program(s)	Hypack® Hardware: GPS, Single beam Transducer, Hysweep.dll (required--passes heading to Hypack® Survey) Hysweep® Hardware: Multibeam Transducer, MRU, Gyro, Hypack.dll (passes position to Hysweep® Survey)
Offset Signs and program(s)	Hypack® Hardware: Horizontal offsets: positive forward and starboard of the origin. Z offsets: Positive upward from the waterline. Hysweep® Hardware: Horizontal offsets: positive forward and starboard of the origin. Z-offsets: GPS in Hypack.dll is positive downward. Transducer: 0--included in draft correction of device when calibrated. MRU: Use zero.** Yaw Offsets: Transducer (determined in Patch Test) & MRU*: positive for clockwise rotation from alignment with the keel. Gyro*: Usually zero. May add correction for variation between magnetic N and true N. Add the variation to the mounting offset using positive values for clockwise rotation from alignment with the keel. Pitch offset: Multibeam sensors (Determined in Patch Test) and MRUs* not oriented directly below the vessel. Positive forward. Roll offset: Multibeam sensors (determined in Patch Test) and MRUs* not oriented directly below the vessel. The reference roll angle (in decimal degrees) is 0 for vertical mounting-use values positive to the port side.
Additional settings	If MRU is not at the vessel pivot point, when you edit your data, check Correct for Induced Heave in the Advanced Read Parameters dialog.

 

5. 2 Single Beam Systems

 

Consideration	Solution
Origin	The transducer that is most important to keep over your survey line.
Hardware Setup Program(s)	Hypack Hardware- All devices
Offset Signs & program(s)	Horizontal offsets are positive forward and starboard Z offsets: Transducer: 0--included in draft correction of device when calibrated GPS: Positive upward

 

B. GPS for heading (1or 2)

 

If you are using 2 GPS and OTFGYRO.dll, the forward GPS is the origin and is the only one where latency offsets should be applied.

 

1. Single Beam

Consideration	Solution
Origin	GPS
Hardware Setup Program(s)	Hypack Hardware- All devices
Offset Signs & program(s)	Horizontal offsets are positive forward and starboard Z offsets: Transducer: 0--included in draft correction of device when calibrated GPS: Positive upward

 

2. Multibeam -- not recommended

 

3. Multi-transducer

The origin is at the GPS. All else is the same as multitransducer systems with a Gyro.

 

4. Single beam and Multibeam-not recommended

 

5. 2 Single beam

The origin is at the GPS. All else is the same as multitransducer systems with a Gyro.

 

A. Towfish

Towfish Offsets and Measurements

 

Offsets for any devices on the vessel are measured from the vessel origin.

 

The cablecnt.dll and towcable.dll in Hypack® Hardware uses the towfish depth, Z?offset and corrected cable length to calculate the horizontal distance from the A?frame connection point to the towfish. That distance is added to the Y?offset to calculate the layback. 

 

Offsets on the Towfish are from the connection point of the cable to the towfish. The hopper arms on a dredge are also configured with reversed horizontal offsets and from the connection point of the arm.

 

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Note: When configuring offsets for the cablecnt.dll or towcable.dll, and the Towfish or other Mobiles in the Hypack® Hardware program, regardless of what type of mobile you have, port and starboard offsets specified in the Offsets dialog must have their signs reversed from the way you normally express offsets for other devices.

 

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Measurements	Normal Device Offsets	Mobile Offsets
Port and Aft	Negative	Positive
Starboard and Forward	Positive	Negative

 

The example below illustrates a towfish setup

 

Towfish with Simple Layback
	Devices	Dialogs
		Driver Setup	Offsets
	GPS		Starboard -5 Forward -5 Height antenna height (not shown)
	Cablecnt.dll or Towcable.dll	Y Offset -20 Z Offset=height above water (not shown)	Starboard -5 Forward 0 Height 0
	Towfish Device		Starboard 0 Forward -10
	Cable out is controlled in the Survey program.

 

Note: In this example, it is also correct to use the following settings for the Cablecnt.dll or Towcable.dll.

 

Devices	Driver Setup	Offsets
Cablecnt.dll or Towcable.dll	Y Offset 0 Z Offset = height above water (not shown)	Starboard -5 Forward 20 Height 0

 

The Track point systems calculate the towfish position. No towfish offsets or cable out distances are required.  

 

Track Point Systems
	Devices	Dialogs Offsets
	GPS	Starboard -5 Forward -5 Height antenna height (not shown)
	Track point	Starboard -10 Forward 20 Height 0

Dredge Systems
	Devices	Dialogs Offsets
	Hopper Arm #1	Starboard 12 Forward -10
	Hopper Arm #2	Starboard -4 Forward 10

 

B. Independent Multiple Vessels

A central vessel can track multiple vessels via radio modems. Set up the devices on each vessel individually. The NMEA.dll can be setup to output GGA, VTG and DBT messages via the radio modem to the data collection vessel. You can also use the Shared Memory NMEAOUTPUT program to send the desired data to the collection vessel. If you will be tracking more than one vessel in this manner, the radio modems must be of different frequencies so that the collecting computer can differentiate between devices.

 

The data collection vessel will have a NMEA.dll configured for each incoming message to receive the data and record data from each sensor separately. The survey screen on the collection vessel can display all of the vessels from which it is receiving data.

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