Because of daily GPS signal scintillation there is a need for redundancy of the dynamic positioning reference systems for vessels that operate in Brazilian waters. Stena Drilling selected the Kongsberg Simrad HiPap 500 for Stena Tay because of its reputation and proven capabilities in deep Brazilian waters. The new system will make the rig capable of acoustically positioning itself while drilling in much deeper water and with significantly higher accuracy.

The HiPap technology is based on a spherical transducer with hundreds of elements mounted around the sphere, all controlled by the APOS software using an advanced signal processing technique. This new technology was designed to obtain optimal position accuracy in deeper waters, in addition to good repeatability and high reliability.

The HiPap 500 system also ensures redundancy of the hardware and position output to the DP. The flexibility of the hardware and software enables Stena Tay to work in Super Short Base Line (SSBL) and Long Base Line Mode (LBL). The system also opens for Multi User Long Base Line Mode (MULBL) where several operators may use the same subsea transponder array simultaneously.

SAIC's Marine Science & Technology Division
Science Applications International Corporation's (SAIC) Marine Science & Technology Division (MSTD), in Newport, RI, has incorporated precise underwater vehicle navigation and positioning into its ISS-2000 product line.

During various survey operations, MSTD has been required to precisely navigate and position underwater vehicles using long baseline (LBL) positioning techniques, as well as ultra short baseline (USBL) acoustic positioning equipment. However, with both of these solutions, a frequent problem is poor positioning during turns and other dynamic maneuvers due to the physical conditions limiting the rate at which position measurements can be obtained.

MSTD developed a mathematical model which showed that infrequent (0.1 Hz) unbiased but very noisy positions coupled with frequent (1Hz) velocity measurements could be expected to produce a continuous stream of very good positions after a system settling time of a few minutes. The measurements were processed in the real-time Kalman filter (RTKF) component that is a standard ISS-2000 module. This technique is known as a complementary Kalman filter.

Measurements conforming to this scenario could be reasonably obtained any time a tethered underwater vehicle is operating within approximately 650 feet (200m) or less of the sea floor. MSTD engineers hypothesized the use of a Simrad HPR 410 Hydro-acoustic position reference system and an RD Instruments (RDI) Workhorse Navigator Doppler Velocity Log (DVL). Information from the manufacturers' data sheets was used to estimate the errors in the model. This model indicated that positioning performance would be enhanced considerably if such a combined system were implemented.

Utilizing an RDI 300 kHz DVL, MSTD developed and integrated the necessary software modules for ISS-2000. The previously integrated HPR 410 was used for the acoustic positions. Following trials that pointed out the importance of correct alignment and calibration of the DVL, results were obtained that substantially verified the results of the modeling phase of this project.

During testing, results were obtained during an approximately 100-meter diameter turn to starboard. The ship's speed was approximately 3.8 knots. HPR positions were obtained every five seconds, and DVL measurements every second. Toward the end of the turn, approximately 30 seconds elapsed with no HPR replies. When a new reply was received, the integrated track was adjusted approximately two meters by the RTKF. This type of result is typical of this combined system and demonstrates that significant improvement in real-time positioning of underwater vehicles can be obtained with positioning and velocity sensors blended in an RTKF such as that implemented in ISS-2000.

While this configuration works well for surface vessels, it is not appropriate for AUVs due to the data path between the vehicle and the surface lacking sufficient bandwidth to carry the velocity data. One solution to this problem is under development by MSTD.

Significant portions of the ISS-2000 real-time system have been ported to an extremely small computing platform running Windows CE, which can be adapted to fit comfortably on most vehicles and requires insignificant power. Initial tests indicate sufficient computational capacity that the complete navigation solution may be formed on the AUV and the relatively modest data requirements needed to get the solution to the surface may be accomplished with a low speed acoustic modem.

Since the 1970s, MSTD has developed integrated systems for survey planning and control, marine data acquisition, and marine data processing and display. They have used ISS-2000 to conduct marine surveys for both commercial and government clients. Over the past seven-plus years, SAIC MSTD has completed multibeam hydrographic surveys for NOAA, as well as seafloor characterization surveys for NRL and UNOLS clients. They provided high resolution imagery of seabed contacts using sidescan sonar and laser line scan systems for hydrographic, mine detection, and search applications, including the crash investigations of TWA Flight 800 and SwissAir Flight 111.

MSTD's Marine Data Processing Center specializes in GIS and data/imagery presentations, while providing rapid data turnaround and multiple display capabilities to enhance bottom feature detection. These capabilities, combined with database development and management expertise, as well as secure, password-protected web distribution, provide near real-time, global geophysical data dissemination to customers. SAIC's MSTD also works closely with clients to determine appropriate solutions for their survey system needs, and has adapted ISS-2000 for specific applications.

Kearfott Guidance & Navigation
The Seaborne Navigation System, or Seanav, is the latest addition to Kearfott's family of inertial quality pointing, stabilization, survey, and navigation devices for maritime operations.

The Seanav's modular architecture provides maximum flexibility, offering selectable performance and future upgradeability. A sophisticated Kalman filter allows for aiding from various onboard devices such as GPS, sonar, Doppler, speed log, aid and screwspeed. Typical applications include patrol boats, surface and subsurface vessels, ROVs, and survey vehicles.

Seanav features include multiple input/outputs, multiple output formats (Geodetic), and at-sea align capable with GPS aiding. The system interfaces with P(y) or C/A code GPS for alignment and aided navigation. Custom displays can be provided to accommodate unique customer requirements. Kearfott is based in Wayne, New Jersey.

Thales GeoSolutions
Thales GeoSolutions (Pacific) has over 20 years of experience providing services and software to the marine survey and positioning industry. Their software engineers have background and field experience implementing and delivering special-purpose systems and techniques that often require unique software and hardware design.

Thales GeoSolutions now offers WinFrog Integrated Navigation System Version 3.2, which combines surface navigation and advanced underwater positioning into one cost-effective package. With over 500 licenses in operation, Thales provides customization for fields ranging from marine survey to underwater construction.

WinFrog's core program provides real-time position and navigation information, and can simultaneously interface with up to 25 types of devices, including GPS, sounders, gyro, USBL and many others. WinFrog currently supports over 300 different devices through either serial or Ethernet communications. It allows the user to define multiple vehicles, each having its own devices, names, offsets, tracks and shapes. In addition, data can be output through industry standard NMEA or customized formats. WinFrog also supports multiple file formats for graphical display, including C-MAP, ARCS and BSB electronic charts, as well as DXF, DWG, DGN, GeoTIF, and others.

In addition to the core program, Multiple Vehicle Positioning & Telemetry (MVP&T), LBL Acoustic, GPS Calculations, and Controlled Remote Tug Telemetry Modules are available.

The WinFrog MVP&T Module supports communication between multiple WinFrog systems using wireless network technology. This module passes positional data between systems so that each system on the network can track and display all vehicles positioned by other networked systems. Primary applications are fleet monitoring, vehicle monitoring systems, meteorological buoy tracking, hazardous materials and environments, anchor handling, dredge monitoring, surf zone surveys, tailbuoy tracking and asset management.

The WinFrog LBL Acoustic Module provides both control and application of the LBL hardware. This module supports full integration of LBL acoustics, with proven acoustic calibration and real-time positioning algorithms, to WinFrog's surface navigation and positioning capabilities. Primary applications are underwater construction, mattress installation, structure mating, jacket installation, pipeline installation, drill ship/rig positioning, precise ROV positioning, and deepwater guideline-less wellhead intervention.

The WinFrog GPS Calculations Module provides enhanced positioning and extensive differential GPS calculation capabilities. This module can combine solutions based on multiple reference stations or multiple RTCM sources into one network solution. Primary applications are pre- and post-dredging surveys, subsea constructions surveys, bottom profiling, hydrographic surveys, submarine cable installations and surveys, tailbuoy tracking, remote tug tracking, and reference station integrity monitoring.

The WinFrog Controlled Remote Tug Telemetry Module enables one WinFrog system to control, monitor, and track other WinFrog systems. This module provides the convenience and control of operating remote WinFrog systems from one controller system, as well as an operational area safety factor. Primary applications are drill rig positioning, pipelay barge operations, cable lay operations, general anchor operations, bundled pipeline tows, and OBC & TZ operations.

RD Instruments
RD Instruments offeres a wide range of Acoustic Doppler solutions to aid in precision navigation. The Workhorse Navigator Doppler Velocity Log (DVL) is a compact and powerful multi-function sensor that provides precise velocity and altitude updates. The unit may be integrated with existing navigation systems including LBL, USBL and inertial systems, or used in a stand-alone configuration. It is currently in use on hundreds of underwater platforms around the world.

The RDI Workhorse Navigator has been designed for use in a variety of applications, including AUVs, ROVs, manned submersibles, mine countermeasures, swimmer delivery vehicles, towed platforms, and diver navigation units.

RDI's patented bottom-detection algorithms, combined with the Navigator's single-ping bottom location, means the unit relocates the bottom on a ping-by-ping basis, allowing for highly robust and reliable bottom tracking even in changing seabed conditions and uneven terrain.

The RDI Workhorse Navigator can reliably track in a variety of seabed materials and compositions, even when the acoustic "brightness" of the reflected signal varies. The unit also automatically adjusts for scenarios where high volume backscatter is generated, such as disturbed sediment and low visibility conditions.

The Workhorse Navigator's four-beam construction provides redundancy, allowing continued operation in the event of a blocked beam or beam failure, and continued bottom-tracking in irregular seabed topography (a 3D solution must have at least three valid beam measurements).

With maximum bottom-tracking ranges of up to 500m and minimum ranges as low as 0.5m, the RDI Workhorse Navigator is capable of providing accurate high rate position and speed information, even when operating close to the ocean floor and regardless of water depth.

The Workhorse Navigator has been quickly accepted within the commercial offshore and military communities. For more information, visit www.rdinstruments.com.

Applanix Corporation
With marine engineering efforts based out of Applanix's headquarters in Toronto, Canada, the company's marine product development efforts continue to benefit from the broad base of motion and navigation talent available in the company's engineering team. Development efforts are currently focused on significant enhancements to their Position and Orientation Systems (POS) MV system to ensure that it continues to build on its position as a leading survey instrumentation solution for hydrographic professionals.

Applanix manufactures precision products that accurately and robustly measure the position and orientation of vehicles in dynamic environments. Applanix POS systems are used in a variety of applications, including seafloor mapping. Established in 1991, Applanix has enjoyed continuous, profitable growth, and now serves customers around the world. It was named one of the fastest growing Canadian companies by Profit Magazine, and was recognized as a leading exporter by FedEx Canada and the government of Ontario.

KVH Industries
KVH Industries is a leader in precision navigation systems for marine, commercial, and military applications. The company also employs proprietary fiber optic gyro technology for system enhancement and as OEM products, offering a range of products suitable for both surface vessel navigation and ROV systems.

The KVH GyroTrac is an economical gyro system that combines two leading-edge concepts: the digital magnetic compass pioneered by KVH and a unique, three-axis gyro sensor. This combination offers the drift-free precision and versatility of digital compass technology with the accuracy of gyro-stabilization, all for less than 25 percent of the cost of traditional gyros. The system's configurable data outputs provide stabilized heading data to virtually all other onboard equipment. It features intelligent auto-calibration and compensation, which ensures the highest degree of accuracy at all times. The system is compatible with NMEA, Furuno, Sine/Cosine, B&G, and Cetrek outputs, allowing GyroTrac to supply stabilized heading data to nearly any onboard system. It also has true or magnetic north output (true north display requires GPS input or manual entry of local variation).

KVH recently introduced its new Digital Signal Processing-based fiber optic gyro (FOG), the DSP-5000. This system represents a breakthrough in low-cost FOG design - an open-loop gyro with outstanding bias stability, low noise, high bandwidth, and scale factor stability of 0.05 percent. The DSP-5000 accepts rate inputs up to 500 degrees per second, offers consistent accuracy over time and temperature, and is available for a fraction of the cost of competing precision gyros. The DSP-5000 combines KVH's proprietary polarization-maintaining optical fiber and fiber components with advanced digital signal processing.

The DSP-5000 is suitable for applications in which gyros and accelerometers are combined to determine vehicle dynamic motions, as well as any application that requires precise measurement of turning angles. The digital output formats minimize problems in sensor integration through a fully digital interface and the use of a single-ended power input. Ideal for use in drone and unmanned vehicle navigation, the DSP-5000 is a versatile, affordable, and reliable solution.

The C100 is an industrial-grade compass module designed to meet rigorous engineering requirements. Available in either a stand-alone or embeddable version, it is physically compact, low in cost, and extremely flexible, making it ideal for the most demanding heading sensor needs. The C100 is based on KVH's proven technology, which has been fielded in more than 100,000 systems for a wide range of military and commercial applications. And with its compact design, multiple analog and digital outputs, and menu-driven software control, the C100 offers unparalleled versatility, making it easy to integrate into any system. Designed to military quality standards with industrial parts, the C100 delivers reliable, trouble-free performance.

LinkQuest
Capitalizing on the acoustic broadband spread spectrum technology used in its acoustic communication and positioning products, LinkQuest has introduced the robust TrackLink USBL systems with superior rejection to ship noise and multipaths.

The low-cost TrackLink 1500LC system, including the transceiver, a transponder, and the tracking software, breaks the $15,000 price barrier and boasts a positioning accuracy of three degrees. The working range is up to 1,500m under typical ship noise conditions.

LinkQuest has also released the TrackLink 1500HA (high accuracy) and TrackLink 1500 MA (medium accuracy) tracking systems.

The TrackLink 1500HA system is a high-accuracy USBL tracking system with an accuracy of 0.25 degrees. The TrackLink 1500MA system is a cost-effective, medium-accuracy system accurate to one degree. These systems have the capability of rejecting severe ship noise and multipath conditions and can operate up to 1,500m of range under typical ship noise conditions. They use the smallest transceiver available to facilitate installation from a ship.

TrackLink systems have integrated high-speed communication functions that share the same hardware and transducer with the USBL tracking system. This unique feature significantly reduces the total system size, weight, and power consumption. It also eliminates acoustic interference that typically exists between acoustic communication and positioning systems. For more information, visit www.link-quest.com.

Sonardyne
The continuing push to develop oil and gas fields in deepwater places increasing demands on acoustic positioning systems often installed on several vessels working in close proximity.

Current acoustic positioning solutions involve the use of different systems by different vessels. While maintaining independent operations between vessels, this inevitably leads to an increase in the volume of acoustic signals being transmitted through the water column. In any field development, vessels very quickly use up the available acoustic bandwidth.

In order to tackle this problem, Sonardyne has resolved to achieve several goals in a next-generation navigation system. There must be independence of operations between the vessels involved in an operation. The achievable precision must be maintained and, if possible, improved when compared to current systems.

Another system goal is that setup must be possible from the DP vessel requiring position. Also, the system must incorporate flexible architecture which allows all current positioning requirements for vessels, ROVs, AUVs, structures, and pipelines.

Sonardyne's future systems will use a combination of acoustic signal processing techniques integrated with external navigation sensors such as INS or DVL. These systems will allow several vessels to operate in close proximity with no interference.

Sonardyne's next-generation solutions will allow DP support vessels to maintain full independence of systems from neighboring vessels, therefore eliminating an element of risk associated with the use of a common reference system. This will also allow any DP vessel to be fully mobile and work anywhere in the world with a dedicated inventory of equipment, without the need for a pre-installed, calibrated, and managed seabed reference system.

The new Sonardyne systems will also allow more flexible operations and faster setup. These factors, combined with those detailed above, will enable vessel operators to save valuable time and money.

Specifics and release dates of the new systems will be announced soon.

Advanced Orientation Systems
Advanced Orientation Systems, Inc. (AOSI) was founded in January 1995 with a goal of developing and producing the next generation of tilt sensors and associated electronic instrumentation. Located just minutes from New York City, AOSI has easy access into a large pool of industrial, engineering, and personnel resources.

AOSI noticed that the major deterrent from using electrolytic tilt sensors was the difficulty of electronic interfacing and signal processing. To solve this dilemma, the company expanded its expertise from sensor development to microprocessor and analog circuit design and sensor interfacing. This diversified AOSI's activities from being a component manufacturer into a system integrator.

An example of this is their EZ-Compass-Dive system, which provides continuous magnetic heading and inclination information up to 11,480 feet (3,500m) deep. The system is housed in a specially designed marine grade aluminum enclosure and fitted with a standard Sea-Con sealed connector. This compass system lets users get reliable heading, pitch, roll and temperature data at a low cost . Easy interfacing of this module via NMEA-183 protocol and fast field calibration saves users valuable time which can be used for other tasks like data collection and analysis, rather than calibration.

For marine applications requiring only inclination data, AOSI offers the EZ-Tilt-5000 dual axis inclinometer. This outputs tilt and temperature information in RS-232, scaleable analog, scaleable PWM formats, as well as two limit switches. It is packaged in the same marine-grade aluminum enclosure and fitted with a Sea-Con sealed connector.

C & C Technologies
Globally Corrected GPS (GcGPS) is a technique used to improve the accuracy and stability of the Global Positioning System (GPS). This technique was developed for NASA due to a requirement for decimeter accuracy in outer space. In order to achieve this level of accuracy at such a great distance from land, a totally new concept for Differential GPS (DGPS) had to be developed. The result of this research has proven to be of value to the marine market, which does not always operate close to existing reference sites or base stations.

This GcGPS technique is of particular value to the international operators that prefer to use one system worldwide. This reduces hardware and training costs, and vastly improves flexibility and safety. The compact hardware design works well for the marine market that often installs antennae at the top of the mast or on small vessels for accurate near-shore positioning.

The name of this C & C Technologies system is C-Nav. The cost of spare hardware is reduced because the same system can be used for various positioning needs. This allows an operator to move from vessel to vessel or to another part of the world and still be comfortable with the positioning system.

C-Nav does not work like conventional DGPS. Conventional DGPS develops a location specific correction message at a reference site. That correction message is then transmitted over some distance to the user, where it is applied to the local GPS measurements. This technique will work as long as the user stays close to the base station to avoid spatial de-correlation issues.

Until about five years ago this was the only method available, but now we have another option. C-Nav works much differently. Think of C-Nav as correcting the errors in GPS at the source of the problem (the satellite and the signal path between the satellite and the user) rather than trying to fix the symptoms of the problem at a reference site.

C-Nav starts with an extensive network of reference sites strategically positioned around the world. Each reference site is equipped with high quality dual-frequency GPS receivers. Many of these sites are equipped with C-Nav hardware that is used for real-time system integrity monitoring. Each reference site tracks all the satellites in view and sends raw GPS measurement data to two independent network processing hubs in real-time. The hubs receive the raw data and calculate orbit and clock correctors for every healthy satellite in the GPS constellation.

These correctors are then broadcast over a network of global communication satellites. The result is a differential correction message that is valid anywhere in the world. This technique eliminates the spatial de-correlation problems that limit conventional DGPS systems. As a result, this is the first truly global DGPS service available, and the accuracies are approaching that of local RTK techniques without the hassles of extra hardware and personnel.

The heart of the C-Nav receiver is a dual-frequency GPS engine with special dual frequency-extended smoothing techniques to allow the use of refraction-corrected measurements. A single tri-band antenna design allows for reception of both GPS frequencies and the Inmarsat L-band communication frequencies. The refraction-corrected GPS measurements and the GPS satellite correction data is fed into the integrated processor. The output is an accurate and stable position from a small and easy-to-operate unit. Only one cable is required, and the hardware is rugged, portable, and can withstand the offshore environment.

In related news, C & C Technologies and Century Subsea have extended their alliance agreement for an additional three years. The alliance provide deepwater construction companies operating in the Gulf of Mexico with a comprehensive range of survey services.

Nautronix
The underwater acoustic environment poses significant problems for the acoustic system designer and has limited the range and accuracy achievable for positioning and tracking operations. Existing acoustic positioning systems rely on MFSK pulses and most manufacturers are trying to squeeze the last vestiges of range from their equipment using increased power, directional beacons and hydrophones and beam forming. All of these methods have limitations.

Nautronix recognized that MFSK pulse technology had reached its limits and, over a five-year period, has applied radio technology to the difficult acoustic environment. The result is Acoustic Digital Spread Spectrum (ADS) signalling.

ADS signalling provides significant benefits in range, accuracy, noise immunity, and interference over MFSK systems. The benefits are so significant that Nautronix developed a complete product range to utilize ADS signalling.

The product range, in addition to the ATS II and RS912, now includes:

• NASNet - a semi-permanent multi-user positioning system capable of achieving ranges up to 15km. NASNet allows all positioning operations in a field to be carried out using one system, with a minimum of seabed stations, thus helping to reduce costs.
• NASPos - a USBL positioning system capable of operating to 4,500km while maintaining 0.25 percent slant range accuracy. It is targeted at the survey, ROV, construction, and cable lay markets, where its long range and accuracy provide improved operational efficiency.
• NASDrill - a family of USBL and SBL positioning systems designed for the drilling market with ranges of 4.5km and accuracy of 0.5 percent slant. These systems can be integrated with Nautronix's other acoustic systems.
• RS925 - a combined SBL/LBL positioning system for reliable deepwater drilling operations.

Nautronix ADS systems are now proving themselves worldwide. On a recent installation the NASPos USBL system achieved 6.3m accuracy in 8,200 feet (2,500m) of water. On another job, the system operated directly through the wash of a tug to provide reliable positioning.

Octopus Marine Systems
Octopus Marine's F180 Inertial Attitude and Positioning System was originally designed for Formula 1 motor racing, but has found its way into the commercial offshore arena.

The F180 is a highly accurate inertial attitude, heading, and positioning system providing high-speed vessel motion data for survey and other offshore applications. It provides heave, roll, pitch, heading, and positioning information in real time.

The F180 has been tested against the current leading alternative and has been shown to be just as accurate, but easier to use, easier to install, more reliable, more cost-effective and - importantly - freely exportable to over 25 countries worldwide.

Some of the Octopus Marine F180's key features and benefits are:

• Self-Calibration and automatic alignment routine - The F180 was developed with the user in mind, by experienced users of inertial technology. The input and feedback by the multibeam engineers and hydrographers who tested the F180 mean it is simple to use, intuitive in design and requires none of the complicated setup and calibration procedures often associated with this type of technology.
• Unique WGS84 Intelligent Strap Down Navigation Module - This contains a precise model of the earth, including transport rates, earth rotation corrections, corriolis acceleration corrections and a gravity model. This enables the F180 to navigate accurately without GPS aiding for short periods of time and to recognize anomalous transient jumps in the GPS position and ignore them.
• A 33Hz 23-State Kalman Filter - The fastest Kalman Filter currently available enables the IMU to track changes and calculate their overall error contribution and correct for these much faster.

The system is designed to measure acceleration forces of up to 10G with no drift resulting in reliable measurements every time regardless of vessel speed and dynamics. It is compatible with all leading multibeam sonars, and available with a flexible pricing structure.