OSPREY - FPSO

Tanker Berthing And Position Tracking

Osprey - The DGPS Tanker Berthing Aid

With the significant development of a reliable global satellite based positioning network GPS technology is now an essential tool in almost all forms of modern position referencing and tracking systems. have adapted this technology to produce a flexible and cost-efficient means of monitoring the relative position of a tanker during berthing at a single point mooring buoy (SPM).

The system is completely self contained and consists of a BASE STATION permanently installed in a terminal control room, a solar powered unit installed on the BUOY, and a lightweight PORTABLE unit to be hand carried onto the approaching tanker. The three units communicate via integral radio transceivers operating on a single UHF or VHF frequency and provide a real time graphical display of the berthing process with sub meter positional accuracy.

	The following data is simultaneously available on both units:
	Relative distance between either the BOW/STERN or CLOSEST POINT from FPSO and tanker  Relative speed and angle of tanker approach  Difference in relative heading (angle)  Absolute FPSO and tanker heading  Absolute tanker speed, direction, and acceleration  Hawser tension

The system provides two basic functions, the first as a berthing aid providing precise information on approach distance, position, and speed. The second is for use as a mooring aid providing audible and visual alarms on collision danger, and more importantly a difference in heading alarm, giving a vital early warning of tanker fishtailing.

If the FPSO is fitted with a hawser tension monitor the signal may be connected to the base station and be transmitted to the tanker unit for display. Again a vital indicator for safe loading. Finally the portable unit is fitted with two pushbuttons that may be user defined e.g. pump control or ESD functions.

Tanker Portable Unit

The tanker portable unit, now a second generation design, consists of a highly integrated device housed in a sealed aluminium briefcase. The unit contains an embedded microprocessor with full colour TFT liquid crystal touch screen, a GPS satellite receiver, a radio transceiver for communication to the FPSO, and a gyroscope compass to determine the vessel heading. All internal components are shock mounted and contain NO moving parts to minimise vibration susceptibility. The unit includes all necessary cables and antennas for operation and once on board the tanker the unit can be deployed on the bridge in less than ten minutes ready for use. Apart from external power there are NO physical connections to the tanker ensuring 100% compatibility with ANY vessel.

	Microsoft Windows NT embedded operating system  266MHz Intel Tillamook Pentium processor  XGA TFT colour LCD screen  Impact resistant TOUCH screen interface  Internal DGPS receiver  Internal 1W radio transceiver  Internal gyroscope compass  Internal loud speaker  Manual ESD I and ESD II pushbuttons  AC/DC wide input power supply  External UHF/GPS antenna with magnetic and clamp fixing

The system employs Microsoft Windows for the graphical user interface providing a familiar environment for the majority of users and can overlay the moving tankers on scanned marine chart of the area for immediate points of reference. User configurable alarm limits are available for each of the above which can sound an audible alarm at both base station and portable unit.

Typical Operating Display

Both the tanker and base station use Microsoft Windows NT as the graphical user interface running the OSPREY application software. The software has been specifically written to be user friendly and with the touch screen interface a novice can master the system in minutes. All options are accessible via menu toolbars which allow the operator to call up any parameter in a small data window at a moment notice.

Two typical screens are shown below. The first details a berthing tanker on its final approach in line with the FPSO. A simulated hawser is drawn on the screen in front of the tanker to visually indicate the optimum mooring distance. The second screen details a moored tanker (connected by hawser) fishtailing around the FPSO. The difference in heading can be set to generate an audible alarm at a operator defined limit.

Vessel Profile

To assist the pilot in deploying the tanker unit the system makes use of VESSEL PROFILES to record the dimensions of the tanker and the previous position of the GPS antenna. The ultimate accuracy of the system depends on how accurately the GPS antenna is placed on the tanker. The configuration screen attempts to assist to operator by asking for the length and breadth of the tanker and then the position of the GPS antenna. Once recorded the configuration may be saved as a PROFILE identified by the vessel name. Thus on the vessel's return visit the configuration may be recalled rather than re entered.

To assist the operator to align the portable unit's gyroscope the window shown on the left may be called at any time to let the operator make a heading correction.

Base Station Unit

The base station unit is a self contained device suitable for either desk or rack mounting. The base station contains an embedded microprocessor, a GPS satellite receiver, a radio transceiver for communication with the tanker, a NMEA-0183 port for connection to the FPSO gyroscope, and a 4-20mA current loop port for connection to the FPSO hawser tension monitoring system. All internal components are shock mounted and contain NO moving parts to minimise vibration susceptibility. The unit includes all necessary cables and antennas for operation simplifying the installation.

The basis behind the operation of a differential GPS system is the requirement of an absolute reference for a non moving base station. The OSPREY system is unique in that it is capable of operating with a MOVING base station (i.e. the FPSO). The base station unit generates the standard RTCM SC104 correction factors and ADDITIONAL information to create a sub meter accurate RELATIVE differential GPS system which allows both the FPSO and tanker to be move in real time. The base station transmits the correction factors to the tanker unit which transmits back its corrected position for display on the base station screens.

To monitor the heading of the FPSO the base station has a NMEA 0183 serial port to interface to the FPSO gyroscope. Note if required a gyro repeater may be supplied to interface to older gyroscopes (e.g. the Anschutz syncro system)

As standard the base station is not supplied with a operator interface. However if the berthing screens are required to be seen at the FPSO a desk top computer may be supplied which can connect to the base station with a CAT 5 Ethernet cable.

Technical Specification

SYSTEM PERFORMANCE

TANKER PORTABLE UNIT

ENVIRONMENTAL DATA

BASE STATION UNIT

OPERATOR DISPLAY

PRINTER