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TZ/ OBC
SHALLOW WATER SEISMIC CABLE POSITIONING

Designed to work with Transition Zone (TZ) and Ocean Bottom Cable (OBC) and
seismic techniques, Sonardyne’s acoustic positioning system significantly improves
the speed, accuracy and efficiency of positioning seabed marine seismic cables.
The system uses a network of low cost, rugged transponders that can withstand fast
deployment through mechanical ‘squirters’ to provide users with an efficient method
of collecting the positions of thousands of seabed hydrophones in real-time and in
water depths from 1 to 500 metres.

System Overview TZ/ OBC at a glance

A typical system comprises of acoustic positioning transponders attached to the
● Proven performance and reliability
seismic cable, a vessel-based acoustic transceiver interfaced to a client’s PC running
the Sonardyne HydroPos software application. Third party software applications ● Long equipment battery life
which incorporate an acoustic control module can also be used with the system.
● Scalable for both small and large
Prior to deployment from a cable lay boat, transponders are attached to the seismic surveys
cable at each ground station to be positioned. Once the cable is laid, the system ● Uses low cost transponders
precisely measures the acoustic range (distance) from a surface transceiver on the
pinging vessel to each transponder to enable its exact position to be established. The ● Operational in 1 to 500 metres
positioning process is more accurate than traditional first break techniques, 1-2 metres water depth
absolute, and can either be conducted once the cable is laid or later whilst shooting. ● Acoustic capacity to position 3600
unique hydrophone ground stations
Transponders
in real-time
The transponders developed for the system are small and lightweight and have been
proven to be able to withstand the demanding and varied operational environment of ● No connection to the seismic cable
surveys. required
● Full integration with automated asset
Standard features of the Type 7815 transponder include a depth rating of 500 metres,
a unique acoustic ‘address’ enabling thousands of units to be laid in a single tracking system
TZ/ OBC
SHALLOW WATER SEISMIC CABLE POSITIONING

deployment and battery voltage monitoring to allow users to better plan their Transponder Options
A range of low cost, rugged transponders are
maintenance schedules.
available including an acoustic release model (right).

Cable Deployment
In operations using a ‘squirter’ cable deployment system, carapaces are available that
provide impact protection for the transponder. The carapaces are manufactured from
ABS plastic that encapsulates the transponder and optional RFID asset tracking tag,
clamping it securely to the cable whilst protecting it from impact and pressure forces
encountered during cable deployment and recovery.

The carapace design, which is now in use with many crews around the world, has
been proven to be easy to fit and reduces long term maintenance when compared
with traditional tie-wrap and tape methods. The low profile shape of the carapace also
reduces the risk of snagging and is acoustically quiet in the water, creating less noise
interference down the cable.

Lightweight Release Transponder

The Lightweight Release Transponder (LRT) offers the same acoustic positioning features
of the Type 7815 but incorporates a unique ‘screw-off’ release mechanism to simplify
equipment recovery. Furthermore, the LRT can be fitted with a bolt-on rope canister that
provides a fast and efficient method of recovering seismic cable back onboard a vessel.

By mooring the LRT and rope canister to the end of the cable, then acoustically
commanding it to ‘release’, the transponder returns to the surface under positive
buoyancy, leaving one end of the rope still attached to the bottom cable. This can then
be hauled onboard and the cable pulled up to the surface.

Acoustic Transceiver
On command from a PC equipped with HydroPos control software, Sonardyne’s
Type 7911 OBC 12 acoustic transceiver interrogates the seabed transponders and
simultaneously takes in DGPS information. This raw data is then pos-processed to
produce ground station positions to better than 2 metres absolute. Data can also be
output to the client’s own navigation processor for independent final network
adjustment.

The transceiver comprises of a rugged waterproof electronics bottle connected to a

remote acoustic transducer which is generally deployed on a pole over the side of
a vessel, or permanently through the hull.
Photo: SMNG

HydroPos V2 Software
HydroPos V2 is a multi-module software programme that allows the user to plan,
Vessel Transceiver
acquire and post process TZ/OBC acoustic positioning data. The software is designed
(Below) OBC 12 is a multi-channel vessel-based
to run on a PC operating either Windows XP or Windows 7 with a recommended transceiver used to measure acoustic ranges.
display resolution of 1024 x 768.

Line data can be imported in OGP P1 and SEG SPS formats as well as a CSV file and
once loaded, transponder locations can be simply added either by ‘hand’ or via the
HydroPos V2 RFiD Cable deployment modules.

During acoustic acquisition, HydroPos commands the OBC 12 transceiver to interrogate

the relevant seabed transponders and logs their acoustic replies. An initial online
positioning solution is available on the acquisition screen with a visual indication of
positioning accuracy.

HydroPos also provides on-line vessel positioning information to the user, to enable
acquisition by the most efficient sail line plan, and at the optimum interrogation speed
and geometry as well as an independent helmsman’s display to provide vessel
guidance. The helmsman’s display is available to all PCs on the same network as the
acquisition PC.
 WWW.SONARDYNE.COM

On completion of data acquisition, the raw data can be exported from HydroPos into
OGP P2/94 or SEG SPS format for submission to the client.

HydroPos is also able to post process the raw data. This simple procedure also allows
the operator the ability to automatically or manually remove any ranges which
obviously do not fit the solution. Data can be processed several times allowing for
different parameters and scenarios to be tried; for example, alterations to sound
speed, solving for depth or fixed depth and tidal corrections.

All raw and processed data is stored in a single, user-selectable, logging file (.LOG)
to allow easy archiving of the data. The recorded .LOG file contains all the online
acquisition parameters as a header, followed by blocks of recorded data. This
enables the data to be easily processed as blocks of data, either at a later date, or at Survey Planning and Acquisition Software
HydroPos V2 is a multi-module software programme
a remote location if required.
that allows the user to plan, acquire and post process
TZ/OBC acoustic positioning data.
RFID Asset Tracking
In large surveys where hundreds of acoustic transponders are deployed, monitoring
equipment movements can be time consuming and inaccurate.
Transponder RFID Tag
Sonardyne’s OBC RFID system automatically logs the identities of transponders and Type 7815 transponders come with the option of a
cables as they are deployed from vessels, together with their associated GPS drop built-in RFID tag to enable crews to track assets during
a survey.
co-ordinates.

The system comprises of four main parts; an RFID software module within HydroPos
V2, reader modules, antennas and small passive RF tags.

During cable deployment, as a transponder fitted with an RF tag passes antennas built
into the chute, its address, channel and asset description is read and logged within
HydroPos V2, along with current GPS location. Using the interfaced surface navigation
data, HydroPos V2 then determines which Receiver Group the transponder is
associated with and automatically includes this information with the line definition in
the property cable file.
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TZ/ OBC Performance Summary TZ/ OBC Key Technology

Operating Depth Range <1m to 500 metres

Operating Frequency Sonardyne HF (35-55kHz)
Acoustic Positioning Capacity 3600 transponders in real time
Positioning Accuracy 1-2 metres absolute
Multiple Target Tracking
Transponder Battery Life Up to 18 months (Alkaline battery) Whether you are conducting a survey in less than
1 metre of water or you’re in several hundred metres,
Required Operating System Windows XP or Windows 7 Sonardyne’s TZ/ OBC acoustic positioning system has
the capacity to position thousands of hydrophone
HydroPos V2 Data Import Format OGP P1, SEG SPS, CSV ground stations in real-time.
HydroPos V2 Data Export Format OGP P2/94

TZ/ OBC USBL Equipment List Key: ● = Required ● = Optional

(Please refer to separate technical datasheets)

Accuracy
Transition Zone and Ocean Bottom Cable surveys
using Sonardyne’s range-range acoustic positioning
technique are more precise than traditional first break
methods, enabling the position of hydrophone ground
stations to be determined within 1-2 metres.
● Software ● Software ● Type 8026 ● Type 7911 ● Type 7815
HydroPos Third Party Navigation OBC 12 TZ/OBC
V2 Acoustic Control Computer Transceiver Transponder

RFID
Asset
Tracking
Automated Asset Tracking
Improve your efficiency. Sonardyne’s Radio
● Type 7986 ● System
Frequency IDentification (RFID) technology automates
LRT RFID Asset
the process of cable asset tracking and database
Transponder Tracking
management by automatically logging the identities
of transponders and cables as they are deployed and
recovered from a vessel, together with their
associated GPS drop co-ordinates.

© Sonardyne International Limited. Specifications subject to change without notice. 05/2012

Battery Life
Operate for longer. Sonardyne’s family of TZ/ OBC
transponders are designed to operate for up to
18 months saving you time and money by not having
to recover equipment to replace battery packs.

Other Acoustic Positioning Systems from Sonardyne

● SIPS 2
● Scout USBL Support
Need to get in touch? Sonardyne’s customer support
● Ranger USBL team are available around the clock to get you the
answers you need. From advice on which product to
● Ocean Bottom Node
use to operational support, it’s all part of the service.