Seapath 200

Accuracy, reliability and simplicity are now more than ever essential features for equipment used in demanding marine operations. Advancements in areas such as hydro acoustic positioning and seabed mapping systems mean auxiliary equipment must keep up. Within these considerations as the measure of our success, Seatex is pleased to present the third generation Seapath. Building on fifteen years of design and field experience with inertial and GPS technologies, this generation Seapath 200 highlights our commitment to supplying the most precise, reliable and easy-to-use heading, attitude and positioning sensor ever!

The best of integrated inertial/GPS
The Seapath 200 provides highly accurate, real-time heading, attitude and position information by blending the best characteristics of sensor-based inertial navigation and GPS continuous position update technologies. High-speed motion data obtained from the system's IMU (Inertial Measurements Unit) and precise position data from two, fixed baseline GPS carrier-phase receivers are integrated in a Kalman Filter within the Seapath Processing Unit. Based on analysis and extensive field testing, the Kalman Filter algorithms have been refined to insure maximum measurement fidelity and reliability.

The Seapath 200 IMU contains highly accurate linear accelerometers and Bosch Coriolis force angular rate gyros (CFG). Real-world precision accuracy is guaranteed by utilising the most accurate calibration methods and sophisticated production equipment available. Roll and pitch accuracy together with the linear acceleration performance are documented for each delivered IMU on a Calibration Certificate.

Robust and reliable
The two, fixed baseline GPS antennas and their receivers that determine precise heading are also used as redundant GPS position and velocity sources. In case of missing data from one GPS receiver, then the other (remaining) receiver provides position and velocity. The Seapath 200 is robust against GPS dropouts by using the IMU to provide position, velocity and heading measurements when GPS is not available.

The Seapath 200 is equipped to utilise up to six different DGPS reference stations to insure robust and reliable DGPS position and velocity measurements. If data from more than six stations are available, the Seapath 200 automatically identifies and uses the six nearest stations.

Measurement data integrity is performed internally by cross-checking data outputs from the different sensors against each other. Noisy data are automatically rejected or reported as inaccurate.

The Seapath provides accurate roll and pitch under all conditions by tightly integrating the GPS and IMU data. With this feature, horizontal accelerations are observable, making the run-ins needed to stabilise conventional vertical reference systems unnecessary.

Visual and flexible configuration
The new version of the Seapath configuration software, SCC, centralises configuration of all parts of the system, including the IMU. A 3D visual presentation of the vessel showing the centre of gravity, antenna and measurement point lever arms is used to simplify and promote an error free installation and calibration. Intuitive Help Wizards assist in system set-up and operation to minimise operator interface and maximise work time.

Output variables and protocols
Third generation Seapath data is available through an Ethernet interface making it easy to distribute the Seapath data to multiple users on board the vessel. Data synchronisation with multibeam echo sounders and other equipment is simplified by the availability of a 1-second time pulse (1PPS) on the Seapath data output. Output protocols for commonly used survey equipment are available on two RS-232 and two RS-422 individually configurable output serial lines and on Ethernet output. All the data are output in real-time, at high update rate, including the position data.

Many applications
The Seapath 200 integrated navigation sensor is an excellent solution for applications such as hydrographic surveying, dredging, oceanographic research, seismic work and offshore construction where accurate compensation of multibeam echo sounders, hydro acoustic positioning systems and ADCP's or vessel motion monitoring are r equired. The Seapath can also be used for continuous calibration of gyrocompasses onboard a vessel.

Integrity monitoring
Data integrity within Seapath is evaluated by monitoring the characteristics of GPS drop-outs, the PDOP GPS constellation parameter and the difference between GPS and MRU measurements. This monitoring is not possible in a single sensor system. The ability to interface and use proprietary differential signals gives Seapath the ability to become a highly accurate positioning tool in its own right.

Navia Maritime AS,
Division Seatex Pirsenteret, N-7462 Trondheim, Norway Phone: +47 73 54 55 00 Fax: +47 73 51 50 20 E-mail: firmapost@seatex.no Homepage: http://www.seatex.no	Seatex Ltd. Suite 1, Old Skene Road, Westhill, Aberdeen AB32 6RL, UK Phone: +44 1224 744625 Fax: +44 1224 744626 E-mail: sales@seatex.demon.uk	Seatex Inc. 911 Western Avenue, Suite 302, Seattle, WA 98104-1068, USA Phone: +1 206 903 8393 Fax: +1 206 903 8394 E-mail: mailbox@seatexinc.com