Features & Benefits

Incorporates Sonardyne's latest Wideband Technology Sonardyne Wideband
Technology provides the highest accuracy and therefore the lowest risk for all subsea acoustic positioning tasks, regardless of water depth.

Enables users to work in close proximity to each other without causing acoustic interference

Intuitive and easy to use software interface

Faster and more efficient vessel operations

Dramatically improved ranging accuracy

Introduction

The primary role for an acoustic positioning system on a mobile drilling unit is to provide accurate and repeatable subsea positioning for the vessel’s Dynamic Positioning (DP) system. Requirements for vessels to work in close proximity to each other and, in some instances, adopt the use of two independent acoustic systems, are demands that further extend the requirement for advanced acoustic signalling technology.

Sonardyne is meeting these challenges with Marksman LUSBL.

Marksman is a new Long and Ultra- Short BaseLine (LUSBL) acoustic positioning system that incorporates Sonardyne Wideband® signal technology to provide precise deepwater positioning, mitigate the problems of interference between vessels and allow multiple systems performing different tasks to be operated on the same vessel.

Sonardyne LUSBL systems have a proven track record on the world’s deepwater drilling and production fleet. Marksman builds upon this heritage by introducing users to the benefits of Wideband signal technology.

Sonardyne Wideband® is the first step-change in performance since acoustic positioning was introduced. It addresses the contemporary requirements of the offshore survey, construction and drilling industries for subsea acoustic positioning, communications and control and in only a few short years has become widely adopted.

Wideband signals are generated through the modulation of carrier frequencies using digital codes. Separation of signals in both frequency and code greatly extends the number of unique signals that can be supported within a defined bandwidth. This generates hundreds of truly independent navigation channels enabling multiple users to work in the same environment without causing acoustic pollution to each other. For example, using Marksman LUSBL, a rig can operate safely on DP whilst simultaneous survey operations are conducted from nearby vessels.

The technology within Marksman provides a dramatic improvement in ranging accuracy and is more robust against the levels of noise created by the thrusters of mobile drilling units.

Wideband acoustic signals are also fundamentally more robust against false detections than traditional analogue signals and are therefore better suited to real time monitoring applications such as the acoustic telemetry of BOP and riser monitoring data.

Marksman’s dual independent capability allows these operations to be conducted in parallel with positioning for drilling operations.

Precise, Robust and Easy To Use
Marksman LUSBL allows a surface vessel to be accurately positioned relative to a seabed transponder array, or multiple subsea targets to be positioned relative to the vessel or array. The system is designed for use as a position reference input for vessels equipped with a DP system or for tracking ROVs or AUVs. DP Class 2 or (DNV AUTR/O) compliant configurations are possible.

The Long and Ultra-Short BaseLine (LUSBL) positioning technique utilised by Marksman is particularly suited to deepwater applications as it combines the repeatability derived from Long BaseLine (LBL) subsea positioning, where accuracy is virtually independent of water depth, with the operational convenience of Ultra-Short BaseLine (USBL) positioning.

The highly robust design of the system ensures that computed vessel position does not degrade, even when a substantial number of signals are lost due to poor acoustic conditions, or due to transponder maintenance. An important benefit of Marksman LUSBL is that the time traditionally required to deploy a seabed transponder array is greatly reduced.

Wideband ranges are at least three times more precise that previous generation analogue positioning systems. This means that baselines can be three times shorter. In 2,000 metres of water, this equates to laying the transponders around a 250 metre radius of the wellhead. As this is within the typical operating reach of a rig-based, work class ROV and TMS system, the vessel can remain in one location throughout the process.

Similar cost savings are generated during the calibration of the array. Marksman’s system architecture circumvents the delays associated with calibrating an LBL array by using a ‘Top Down’ technique as the transponders are deployed. By not having to take baseline measurements, the array can be calibrated quickly and reliably.

System Overview
A Marksman LUSBL system is comprised of a Navigation Processor, Navigation Computer, software, subsea transponders and a vessel-based acoustic transceiver. When configured for dual independent operations, the vessel is equipped with two separate, time-synchronised sets of topside hardware that share the same seabed array.

The Navigation Processor and Navigation Computer are the core of the Marksman system and are designed to meet a complete onboard hardware requirements of any LBL, USBL or LUSBL acoustic operation.

The Navigation Processor is the interface between the in-water acoustic instruments, sensors and the Navigation Computer which runs the Marksman acoustic positioning software.

The Navigation Processor commands the transmission of acoustic signals from the through-hull acoustic transceiver to the seabed transponders, decodes the data received back and formulates the appropriate telegram to pass to the DP desk.

In addition to accurately time stamping incoming data from external devices such as attitude and heading reference units (Lodestar, P07) and GPS, the Navigation Processor also provides power and communications for the vessel’s acoustic transceiver.

A range of hardware interface cards are available for interfacing Sonardyne transceivers and external sensors. By simply plugging these cards into the rear of the unit, the role of the Navigation Processor can be transformed from supporting simple to complex acoustic operations.

The Navigation Computer is a powerful, purpose-built PC that has been specifically designed to run Sonardyne’s family of acoustic navigation software applications. Features include a front-mounted software key port for when access to the rear of the unit is restricted by rack mounting.

The operator interface consists of a rack mountable TFT colour monitor and keyboard. This facilitates system initialisation, whereby job specific parameters can be changed and positioning tasks monitored. Dual screen and touch screen options are possible.

Alternatively, the Marksman LUSBL display can be integrated within a customer’s own DP console

Software
Marksman LUSBL software is a Windows-based package that is responsible for collecting, processing, displaying and recording acoustic positioning operations. Developed in close co-operation with end users, Marksman's modern user interface is easy to set-up and intuitive to use.

During set-up, the software automatically identifies the type of transceiver connected to the system and configures it accordingly. Multiple attitude, heading and position instruments can be added in a simple I/O ports page which provides feedback on the operation of all inputs and outputs. Adding transponders to a job is simple and once the system is configured, tracking can be turned on and off with a single click.

Included within the package is an extensive array of tools to allow the user to optimise the performance of the system during set-up, calibration and LUSBL positioning operations. These include utilities to measure acoustic noise, a signal analyser to filter out a specific transponder's signal and a communications viewer to monitor Navigation Processor and Navigation Computer serial port activities. To correctly calibrate gyro and VRU offsets and therefore improve positioning accuracy, Sonardyne's CASIUS calibration tool is also included.

A range of audible and visual alarms for loss of instrument data are available to the operator.