OSPREY - SINGLE POINT MOORING

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 FPSO.

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

	The system provides the following information:
	Relative distance (CLOSEST POINT) between SPM and tanker  Relative speed and angle of tanker approach  Difference in relative heading (angle)  Absolute tanker heading  Absolute tanker speed, direction, and acceleration  SPM mooring position  Hawser tension (with load pin installed on buoy)

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 SPM is fitted with a hawser tension monitor the signal may 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 SPM, 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 tanker 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. They both detail the tanker on approach to the SPM buoy. The approach distance, speed, and bearing are displayed along with the SPM turntable heading and the tanker heading. With additional instruments on the SPM the wind speed and direction and sea current speed and direction may also be displayed. All provide additional information during berthing.

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.

The System

The OSPREY system consists of three units, a non moving base station to provide an absolute reference for the differential GPS system, a unit on the SPM buoy, and the tanker portable unit. The base station generates DGPS correction factors which are then transmitted to the other units to correct their position to a sub meter accuracy.

Buoy Unit
	The buoy equipment consists of a self contained, solar powered unit, containing an embedded microprocessor, a GPS satellite receiver, and a radio transceiver. All components are housed in a rugged marine protected outer enclosure suitable for drop installation onto the SPM turntable. All components are shock mounted and contain NO moving parts to minimise vibration susceptibility. In addition to the buoy position, the hawser load, wind speed/direction, and sea current speed/direction may be monitored and transmitted to the other units for display.
Base Station Unit
	The base station unit is a self contained device, suitable for either desk or rack mounting, containing an embedded microprocessor, a GPS satellite receiver, and a radio transceiver. 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. As standard the base station is not supplied with an operator interface. However if the berthing screens are required to be seen at the terminal a desk top computer may be supplied which can connect to the base station with a standard CAT 5 Ethernet cable.

Technical Specification

SYSTEM PERFORMANCE

TANKER PORTABLE UNIT

ENVIRONMENTAL DATA

BASE STATION UNIT

OPERATOR DISPLAY

PRINTER