Applications of iUSBL
Technology overview
Tom Bennetts
Project Manager
www.sonardyne.com
Summary
1. What is iUSBL and its target applications
2. Advantages of iUSBL and sample data
3. Technical hurdles and Calibration methods
4. Improvements using Lodestar with iUSBL and an Inertial Navigation Solution
www.sonardyne.com
What is the “i” in iUSBL
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Standard USBL systems usually hull mounted on the ship
Ultra short baseline to calculate azimuth and elevation the
acoustic signal arrives from.
Combine with GPS, Heading, Pitch & Roll at time of acoustic
receipt to give a transponder position
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Inverted USBL for operating at depth
Traditional vessel mounted USBL but with a
pressure balanced array for deep water use
Rated to 7000m
Utilises Sonardyne Wideband signals for
optimal accuracy
Can be used in any orientation giving rise to
many applications
www.sonardyne.com
Which way is it facing?
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The iUSBL already has a basic internal sensor but typically we want better than 0.5% SR
This involves mechanically mounting a Lodestar AHRS to the iUSBL
Installed in a multitude of survey scenarios on any vehicle
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Customers have approached Sonardyne with particular operational circumstances well
suited to iUSBL
www.sonardyne.com
Who uses iUSBL
Example applications
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Deep water Oceanographic research
AUV docking and position re-initialisation or beneath extensive ice sheets
ROV positioning single reference ROV tracking instead of a full LBL array
Accurate streamer tracking for hydrocarbon mapping such as seismic & EM
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Review each application where the system is being used in a alternative way
from standard vessel mounted USBL.
Highlight the technical advantage
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www.sonardyne.com
NOC – Ultra deep water tow-fish tracking (6,000m range)
Bay of Biscay 2007 - present
•Ultra long range requirement
•Potential to deploy without surface USBL
•iUSBL rated to 7000m
www.sonardyne.com
Deep Tow Fish Tracking
Towed Ocean Bottom Instrument (TOBI 2)
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Used for very long ranges as the local
SNR is very good
www.sonardyne.com
AUV Guidance & Docking
2007 – Present
•AUV nose cone with iUSBL transceiver
•Also includes many military applications
Avtrack Navigator
iUSBL with & high speed
acoustic modem link
Sends data back to the surface
www.sonardyne.com
AUV Docking
>1500m @ 15m shallow!
Cross track
error
Bearing error
1,800 m
www.sonardyne.com
ROV Based USBL
Single reference tracking
The ROV could track a mobile transponder
outside the vessels USBL operating field or
in/under a structure
iUSBL mounted
on ROV
Vessel of
opportunity
ROV can be
tracked from the
vessel If vessel
based USBL is
available
ROV tracking relative
to a fixed reference
transponder
www.sonardyne.com
Streamer tracking, Singapore, Norway, Shetland, Atlantic and India
2007 - present
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Mounted on a subsea vehicle
Facing rearward to track a Streamer
www.sonardyne.com
iUSBL & Lodestar – An application used by Fugro
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A
GPS positions Vessel USBL
AHRS stabilises the USBL to
position Tpdr A
iUSBL and Lodestar position Tpdr B
B
www.sonardyne.com
Streamer tracking
Detecting ballast bias along the streamer
www.sonardyne.com
dx
Beacon separation
Streamer tracking
Mapping separation - seismic or electromagnetic Tx & Rx
Knowing the exact separation helps Geophysical interpretation of data.
The exact position of the Tx and Rx are known better than if the locations been
derived from a surface USBL.
www.sonardyne.com
Technical advantages of iUSBL
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Operates beyond the range of a standard vessel based USBL system
Usually situated in low noise & low reverberation
Dynamically stable environment
Increased range capability due to better SNR
Positioning is locally accurate irrespective of depth
Shallow tracking where thruster wash would have been an issue
No re-calibration required
Rapid deployment – vessels of opportunity
Installed on most subsea bodies
Compatible with 3rd party survey systems
www.sonardyne.com
Removing the transceiver from the vessel away from vessel noise
Example from a particularly noisy vessel
Noise plot taken from vessel’s USBL
Observed noise @ 26kHz = 109dB
Example:
SNR
Theoretical
max range
USBL
6.94dB
2,398m
iUSBL
32.94dB
7,864m
Ambient noise observed away from the vessel
Observed noise @ 26kHz = 78dB
Observed noise drops from
109dB @ 26kHz to 78dB = 31dB reduction
www.sonardyne.com
NOC ~ 6000m Range
iUSBL origin
Transponder deployed from vessel
potentially no surface USBL
Transponder in Responder mode
6000m
Ping stacking to give 2Hz update
irrespective of range
iUSBL Dynamically
stable low noise
environment Good SNR
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Achieving up to 10km
Trenching work
Conventional vessel based USBL
Tracking to head towfish with USBL
Total distance between vessel and
tail towfish could be over 10km
iUSBL mounted on
head towfish or cage
facing aft
iUSBL tracking Trencher
10,000m
www.sonardyne.com
Rapid deployment
A combined
Subsea Lodestar
AHRS and MF
iUSBL tracking
trial before being
mounted on an
ROV or AUV.
www.sonardyne.com
Vessel Based Remote USBL – The Application
iUSBL Positioned Towfish B
Tail towfish
being
positioned
via the iUSBL
Multiple
Transceivers
require Fusion
USBL
GPS
positioning
vessel USBL to
transponder to
iUSBL to
target
www.sonardyne.com
Mixing survey system tracking a mobile Compatt from the iUSBL
Customer demos Plymouth 2008
Sonardyne or
Alternative
vessel based
USBL
positions the
iUSBL vehicle
The output from the
vessel USBL system
and Sonardyne iUSBL
can be combined in a
navigation package to
provide overall
positioning
Sonardyne
iUSBL
positions
the mobile
target
www.sonardyne.com
Operation problems to overcome
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Sound velocity compensation
Depth aiding iUSBL position
Calibration
Stable vessel USBL position of towed body where iUSBL is mounted
www.sonardyne.com
Sound Velocity
Horizontal application
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Importance of Mini SV sensor
SV varies with depth therefore fast update required
www.sonardyne.com
Depth aiding
At depth any errors in USBL derived depth are directly transferred to the iUSBL positions
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Compensate with onboard pressure sensor
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Pulse position depth on WSM beacons
Example of poor depth input
degrading all data of the relative
system
Improved by adding pressure
sensor data to the USBL position
for the towed iUSBL
www.sonardyne.com
Calibration
Orientating the AHRS to the iUSBL
Co-ordinate Measuring Machine
at Sonardyne head office
Accurate enough to highlighted a 0.1
deg roll error in 3rd party vessel USBL
system in 1500m
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We can further improve this…….
www.sonardyne.com
Improving iUSBL positioning
• Tightly coupled USBL
• INS aided subsea positioning
www.sonardyne.com
Lodestar on vessels of opportunity
Over-the-side can provide excellent results if care is taken
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Understand twisting, flexing and motion of the pole relative to the vessel
and compensate (Lodestar AHRS) appropriately.
Lodestar mounting plate
www.sonardyne.com
USBL System Performance
An Average Fix in Deep Water for such operations
• Data is merged at
source
Easting vs Northing
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• One time platform
•Access to all high speed
Data
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5
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Not limited to bandwidth of
232
•Immune to pole
movement
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2,070m
Wideband vs Tone
-15
An Average Fix in 2,070m Water Depth
SD Eastings
1.16m
•No induced errors from
ship distortion where
AHRS is on bridge
SD Northings
SD Depth
1.18m
0.17m
www.sonardyne.com
INS on the towfish
It’s was there all along!
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Lodestar was designed as an inertial system from the start
Firmware upgrade to enable inertial output
Combined with surface positioning gives the ultimate iUSBL positioning
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Lodestar at surface to
stabilise the vessel motion
Tightly coupled USBL
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Aid positioning in deep
water of towed body
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Lodestar subsea to stabilise
the surface USBL position
for the towed body
Tightly coupled iUSBL
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www.sonardyne.com
INS proven track record demonstrated at OB09
Real time DVL, USBL and LBL aided INS
Integrated DVL, SV, Pressure
and USBL into one solution
www.sonardyne.com
Sonardyne family of Transceivers
To meet your survey requirements
Do you have a new application?
We have the solutions iUSBL is core
to our next generation of products
Avtrack Navigator
•Subsea iUSBL
•Acoustic modem
HP USBL
•High Precision USBL
•Coupled AHRS
•Combined Inertial system
www.sonardyne.com
www.sonardyne.com/Products/PositioningNavigation/8091_8094.html
Tom Bennetts
Project Manager
[email protected]
Head Office
Sonardyne International Limited
Blackbushe Business Park
Yateley, Hampshire, GU46 6GD
United Kingdom
T. +44 (0) 1252 872288
F. +44 (0) 1252 876100
E. [email protected]
www.sonardyne.com
www.sonardyne.com