Standby and Port-Security Mode for Detecting Watercraft Drift, Mooring Failure and Unauthorized Movement

Defensive Prior Art Disclosure

Standby and Port-Security Mode for Detecting Watercraft Drift, Mooring Failure and Unauthorized Movement

Statement of Intent

This publication is a defensive prior art disclosure. Its purpose is to make the described watercraft monitoring methods publicly available and usable as prior art against later patent applications.

No exclusive patent rights are asserted by the author over the expressly disclosed concepts.

Technical Field

The disclosure concerns low-power monitoring of an unattended boat or other watercraft while it is:

• moored in a marina;
• tied to a bank or pontoon;
• anchored;
• stored on a trailer;
• kept at a rental base;
• left temporarily without crew.

Background and Technical Problem

An unattended vessel can move because of anchor drag, a broken mooring line, changing water level, wind, current, collision, unauthorized towing or theft.

A simple circular GPS geofence is often insufficient. A moored or anchored vessel normally moves within a limited area. GNSS measurements also vary even when the vessel is stationary. Setting a very small radius creates false alarms, while a large radius delays detection.

Continuous GNSS and cellular operation can also discharge a small vessel battery.

Summary of the Disclosed Solution

The disclosed system provides a standby or port-security operating mode. It establishes a reference state, observes motion using a low-power sensor and selectively obtains position fixes. Movement is classified using a combination of displacement, direction, time and inertial activity.

The system distinguishes ordinary bounded movement from persistent displacement and generates different events for possible anchor drag, mooring failure, trailer transport or unauthorized movement.

Components

An exemplary implementation contains:

• a processor;
• an inertial measurement unit;
• a GNSS receiver;
• non-volatile memory;
• a local or wide-area transmitter;
• battery-voltage measurement;
• optional ignition, shore-power, mooring-line, water-level or door sensors.

The device may be part of a full onboard computer or an independent security tracker.

Arming the Mode

The mode may be armed manually through a phone, automatically when ignition is switched off, when the vessel enters a marina zone, when a rental trip ends or when the craft remains stationary for a configured time.

During arming, the system records a reference set comprising some or all of:

• averaged GNSS position;
• GNSS accuracy estimate;
• current heading;
• expected movement radius;
• anchor or mooring state;
• water level or tide information;
• battery condition;
• arming time;
• authorized user proximity.

The reference position may be calculated from several fixes rather than one fix.

Low-Power Observation

After arming, the GNSS receiver and wide-area modem may be deactivated. A low-power accelerometer remains active and generates an interrupt when motion exceeds a configured level.

The processor also wakes periodically to obtain a verification fix. The verification interval may be selected from predefined values based on whether the craft is anchored, moored or stored on land.

Bounded Movement Model

Ordinary movement may be represented by an allowed region around the reference position. The region need not be circular. Examples include:

• a circular swing area for an anchored boat;
• an arc or sector based on anchor location and rode length;
• an elongated region parallel to a pontoon;
• a narrow region around a trailer position;
• a polygon defined by a marina berth.

The allowed region may include an added margin corresponding to current GNSS uncertainty.

Persistent Displacement Detection

A possible movement event is identified when one or more fixes fall outside the allowed region. Before issuing the final alarm, the system may obtain additional fixes at shorter intervals.

A confirmed displacement may require:

• a minimum distance beyond the boundary;
• persistence for a defined duration;
• successive fixes showing a consistent displacement direction;
• inertial activity compatible with actual motion;
• absence of an authorized ignition or disarming event.

This confirmation stage reduces false alarms caused by a single inaccurate position.

Movement Classification

Different movement patterns may produce different event categories.

Possible anchor drag

The vessel remains on the water, moves predominantly downwind or down-current and changes position gradually while remaining near the original anchoring area.

Possible mooring failure

The vessel leaves a berth-shaped allowed region and continues moving with current or wind without an authorized start event.

Possible towing or theft

The vessel exhibits sustained movement, increasing speed or departure along a navigable route while ignition is off or no authorized user is present.

Possible trailer transport

The system detects vibration and speed characteristics associated with road travel, optionally combined with a position outside the water area.

The above classifications may be implemented using deterministic thresholds and rule tables.

Alarm Escalation

An exemplary escalation sequence is:

1. record a local pre-alarm event;
2. increase position sampling;
3. activate a local light or sounder if configured;
4. send a short warning to the owner or fleet operator;
5. continue transmitting current position at a higher rate;
6. downgrade or close the event if the craft returns to the allowed region;
7. retain a history containing positions and sensor states around the event.

Alarm messages may include the reason, confidence level, last valid position, direction of movement, speed, battery status and age of the information.

Communication Failure

If no wide-area network is available, the alarm and associated samples are stored locally. The system repeatedly attempts delivery according to a limited retry schedule.

A sub-gigahertz link to a marina or rental-base receiver may operate independently of cellular coverage. A nearby authorized phone may also retrieve a pending alarm through a local connection.

Battery Protection

If vessel battery voltage falls below a threshold, the system may:

• extend routine verification intervals;
• suppress nonessential history uploads;
• retain sufficient energy for motion-triggered alarm transmission;
• generate a low-battery warning before reducing activity.

The security function may be powered from a separate reserve battery after loss of vessel power.

Example Implementation

A small motorboat is moored alongside a pontoon. When ignition is switched off and the boat remains stationary, the user arms port mode. The device averages ten GNSS fixes and creates an elongated permitted polygon corresponding to the berth.

Two hours later, the accelerometer detects sustained motion. The GNSS receiver obtains three fixes outside the polygon. The positions show movement away from the pontoon and no authorized ignition event exists. The system classifies the event as possible mooring failure or unauthorized movement, transmits an alarm and starts a higher-rate position history.

Variants

The system can be adapted to:

• anchor-watch operation;
• marina berth monitoring;
• bank mooring on rivers with changing water levels;
• rental fleet storage;
• trailer theft detection;
• temporary stops during a voyage;
• monitoring floating docks, buoys or other floating assets.

Technical Effects and Advantages

The disclosed solution provides:

• lower energy consumption than continuous GNSS and modem operation;
• fewer false alarms than a single fixed-radius geofence;
• distinct classification of several movement causes;
• useful operation where cellular coverage is intermittent;
• recorded evidence of the vessel's movement after an incident.

Technical Concepts Disclosed for Prior Art Purposes

This publication expressly discloses:

1. a watercraft standby mode using a low-power motion sensor to wake GNSS verification;
2. berth-, anchor- or trailer-specific noncircular allowed regions;
3. confirmation of movement using multiple successive fixes, time and IMU activity;
4. rule-based classification into anchor drag, mooring failure, towing, theft or trailer movement;
5. escalating position-sampling and message frequency after a suspected incident;
6. reserve-energy protection for alarm transmission;
7. store-and-forward alarms and optional sub-gigahertz delivery to a shore receiver.

Public Availability Declaration

The expressly described concepts are made available for public implementation, modification and extension. The purpose of publication is to establish public technical disclosure of these methods and combinations.