Ship Surface Speed Calculation via AIS Trajectory and Environmental Drift
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Solution Overview
Problem
Current methods for measuring the surface speed of ships and environmental parameters like sea currents and wind are either inaccurate, costly, or limited in spatial and temporal resolution, and often require specialized on-board sensors, making it difficult to monitor multiple ships simultaneously in operational conditions.
Innovation Solution
A method using external means such as AIS, radar, and remote sensing systems to calculate the surface speed and drift vectors of ships by obtaining navigation and environmental parameter measurements near the ship, without the need for on-board sensors, allowing for real-time and high-resolution measurements of surface speed and environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If navigation tests are carried out before vessel is put into operational service to establish correlation table between engine rpm and surface speed, then surface speed values can be estimated under normal navigation conditions, but this method requires obtaining information on engine speed via specific on-board sensor and cannot be used by shore-based service to simultaneously measure surface speed of multiple ships
Solution Approach 1:
The method uses the ship's own trajectory data, heading, and speed over ground from AIS to calculate surface speed without requiring external sensors or pre-established correlation tables. Each ship serves itself by using its own navigation parameters and environmental measurements to determine its surface speed, eliminating the need for ship-specific calibration data
Solution Approach 2:
Environmental measurements (current and wind) act as intermediaries that connect the observable trajectory data to the unobservable surface speed. By measuring drift caused by environmental factors and combining this with trajectory information, the method indirectly determines surface speed without requiring direct sensors on the ship
2Measurement precision
If on-board speed sensor (log) is used to measure relative speed of vessel with respect to water surface, then surface speed information is available on board, but this information is not directly available to land-based monitoring service
Solution Approach 1:
The method creates a feedback loop where AIS trajectory data is continuously updated and processed to recalculate surface speed in real-time. The land-based service receives ongoing updates of position, heading, and speed over ground, which are fed back into the calculation algorithm to maintain current surface speed estimates without requiring direct sensor data transmission from ships
Solution Approach 2:
The patent replaces the mechanical sensor-based measurement system (log) with a computational system that uses electromagnetic communication (AIS) and environmental measurements. Instead of relying on physical sensors on each ship, the method substitutes a land-based computational approach that processes readily available navigation data
3Measurement precision
If drifting buoys are used to measure surface current, then current measurements can be obtained, but equipment is poorly suited to coastal areas, data is available in delayed time, and equipment acquisition and deployment costs are high
Solution Approach 1:
The method performs preliminary calculations by combining trajectory data with environmental measurements in real-time as ships pass through monitoring zones. Surface current and wind conditions are determined proactively during ship passage rather than waiting for buoy data collection cycles, providing immediate results for navigation optimization
Solution Approach 2:
Instead of deploying physical buoys in the water, the method creates a virtual measurement system by copying and processing the motion data of passing ships. The trajectory information from multiple ships serves as a substitute for direct water column measurements, providing current data without physical deployment in hazardous coastal areas
4Loss of time
If HF or VHF radars are used to measure surface current, then measurements can be made in near real time, but surface area of measurement zones is small, spatial resolution is low, and equipment is very expensive
Solution Approach 1:
The method makes AIS systems, originally designed for ship identification and collision avoidance, multi-functional by adding surface current and wind measurement capabilities. The same AIS infrastructure used for navigation safety now provides environmental data, eliminating the need for dedicated radar systems and expanding measurement coverage to all AIS-equipped vessels in the area
Solution Approach 2:
The patent transitions from two-dimensional radar scanning of fixed zones to three-dimensional utilization of ship trajectory data across extended navigation routes. By processing position, heading, and speed over ground along entire ship paths, the method effectively expands the measurement volume and coverage area beyond what fixed radar beams can provide
Data Source
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AI summary
The invention relates to a method for calculation of the surface vector of at least one ship moving with the engine at cruising speed, characterised in that it comprises the following steps at a determined position of said ship (1): a) obtaining the parameters of said ship (1) including the position, bearing, surface speed, surface course; b) obtaining measurements selected from the wind and the current using means external to said ship (1), said measurements being performed in the proximity of said ship (1); c) defining the drift vector from the measurement(s) obtained in step b) selected from the wind and the current; d) defining the surface vector from the parameters selected from the position, surface speed and surface course in step a); and e) calculating the intensity and direction of the surface vector of the ship (1).