Key Features

Incorporates Sonardyne's 6G® Technology

Incorporates Sonardyne's Wideband 2® signal Technology

Dramatically faster and easier to set-up, calibrate and operate

Single box solution for motion 
sensor and gyrocompass

Provides an independent DP reference

Ride through capability - resilient to effects such as aeration and noise

LUSBL accuracy from a single transponder

Independence from GPS disruptions

Update rates to match DP model

Three fold improvement over standard USBL repeatability

Potential for fuel and operational savings

Brochure

DP-INS (PDF)

DP-INS (Digital Version)

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Sonardyne DP-INS is a new, inertial navigation-based Position Measuring Equipment (PME) source for dynamically positioned (DP) rigs and vessels. The independence and redundancy provided through inertial augmentation of Sonardyne’s Marksman and Ranger 2 acoustic positioning systems delivers improved performance and safety whilst reducing operational cost. DP-INS combines the complementary characteristics of the latest Sonardyne Wideband® 2 acoustic signal technology with high integrity inertial measurements. The resulting output is resilient to acoustic disruptions and completely independent from GPS.

The seamless integration of acoustics and inertial technologies exploits the long term accuracy and precision characteristics of acoustic positioning with the continuous availability and fast update rate from high grade inertial sensors. A single navigation solution is computed and output to a display with intuitive status and quality metrics. Standard output telegrams are available for Converteam, L3 or Kongsberg DP systems.

The independence offered by Sonardyne DP-INS significantly reduces operational delays during periods of challenging subsea acoustic conditions such as aeration and noise. In addition, the high update rate and independence from GPS will allow the vessel to continue operating in periods of GPS instability or outage caused by effects such as GPS signal scintillation.

DP-INS does not need a full seabed Long BaseLine (LBL) array and can be used with a single transponder deployed below the vessel. This significantly reduces the set up time following arrival on location. The need for only occasional acoustic aiding provides additional operational cost saving benefits by extending transponder life and thereby reducing maintenance operations.

Dynamically positioned vessels operating in deep water have traditionally relied exclusively on GPS and subsea acoustics (LUSBL or USBL) as their two primary types of position reference. There has always been a recognised need amongst operators for an independent DP reference that would allow safe rejection of a positioning error in one of the other two reference types. An example of the need for an independent reference exists in Brazil where scintillation can degrade GPS positions leaving the LUSBL system as the sole reference.

Sonardyne’s DP-INS system addresses this need by offering an acoustically aided inertial navigation solution.

Lodestar Hardware Platform

The core of the system is the Lodestar platform. Lodestar was released to the market in 2007 as a premium quality, survey grade Attitude and Heading Reference System (AHRS) for surface and subsea applications. Using the same hardware platform, Lodestar is now configurable for acoustically aided INS operations for tightly integrated DP vessel applications.

Lodestar makes use of three ring laser gyroscopes that measure the angular rate and three accelerometers that measure the specific force of a moving platform. The highest quality dual use (commercial and military) field proven sensors have been selected for use due to their performance, low mean time between failure (MTBF) and ease of export. These sensors have highly stable error characteristics and are compensated for temperature variation making then ideally suited to DP applications.

The INS sensor outputs are combined mathematically to compute the position, velocity and attitude of the vessel. The output is extremely low noise and very accurate in the short term but slowly degrades over time. Therefore it is necessary to seamlessly aid the INS with complimentary acoustic positioning observations.

Acoustic Aiding Input

DP-INS system uses a tightly coupled integration of range and bearing from at least one transponder to aid the INS and control integration drift. This approach makes optimum use of Sonardyne Wideband acoustics to exploit and enhance the positive characteristics of the inertial sensors.

Sonardyne’s latest Sixth Generation (6G®) vessel-based transceivers and subsea transponders maximise the benefits of the system by providing the most precise and reliable acoustic aiding input. Whilst only one transponder is needed to aid navigation, two are typically deployed if equipment redundancy is required. Before the system is used operationally, the vessel’s GPS receiver is used to calibrate the real world position of the transponders. Once this is complete, the system no longer requires GPS as an input. Previous generation Sonardyne transceivers and transponders are also compatible with DP-INS.

Bridge Installation

The Lodestar INS unit and acoustic transceiver are interfaced to, and powered from, the bridge using the Lodestar Communications Hub (LCH), itself connected a dedicated Navigation PC running the Marksman LUSBL or Ranger 2 USBL software applications.

The Navigation PC is a powerful, purpose-built unit that has been specifically designed to run Sonardyne’s family of acoustic and inertial navigation software applications. 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 software display can be integrated within a customer’s own DP console.

The vessel’s Marksman and Ranger 2 software displays both the vessel’s LUSBL or

USBL position and the INS position in an intuitive format alongside essential status information. The display gives the system operator access to all the information required to monitor DP-INS performance without significantly increasing their workload.

Wiring

For Lodestar, three screened twisted pairs are needed for signals plus a single core for a ground reference (four twisted pairs in total will cover this). Also, two power cores (12 AWG) are needed. Ethernet options are also available.

For the acoustic transceiver, which can operate in either LUSBL or USBL mode, two screened twisted pairs are needed for signals plus a single core for ground reference (three twisted pairs in total will cover this). Also, two power cores (12 AWG) are needed.

Depending on configuration, or where existing ship’s cabling is limited, it is sometimes possible to combine Lodestar and USBL transceiver serial cabling and power the transceiver directly from the Lodestar.

Transceiver and Lodestar Deployment

In order to provide optimum system performance, it is important that the inertial and acoustic systems experience the same dynamic motion. Therefore the Lodestar INS and vessel’s acoustic transceiver should be co-located on the same deployment pole using a through-hull or stem tube arrangement.

Sonardyne’s through-hull deployment machine has a stiff, one piece Inconel clad steel pole that hydraulically lowers and raises the transceiver through a gate valve. A sea chest with inspection hatch allows for ease of installation and cleaning of the transceiver. Sonardyne also offers a through-tube method of transceiver deployment for convenient retrofitting systems to older vessels. Refer to separate brochure for more details.

The typical accuracy (excluding systematic error) of Sonardyne DP-INS when compared to other PMEs is shown in table the below: