HULL

Technical field

The present invention refers to a method and an apparatus for detecting abnormal movements of a moored boat hull. Technical background

A typical dock for a watercraft comprises a limited space defined between a jetty and two slips extending substantially perpendicularly from the jetty. Numerous systems are available to facilitate the docking procedure to give the operator information about the watercraft's direction and orientation. One parameter to consider is the position of the watercraft's fore relative to the dock and the slips during approach. The second critical component is the orientation of the watercraft with respect to the fore. Both types of information are critical, since a failure to maintain alignment of the watercraft's aft may cause a crash. What further complicates this operation are outer parameters, such as wind or water currents. Prior art includes numerous attempts to address these difficulties. It is by way of example well known to use equipment such as cameras fixedly arranged to the watercraft or laser beams in order to give input to the operator during the docking. It is also known to use cameras or sensors that are fixedly arranged on the jetty in order to provide information to the marina whether the dock is occupied or not. This information can be used in a booking system to see availability or to arrange for payments etc.

The actual usage time of a watercraft is typically very limited. Once docked, the watercraft will often be left without surveillance for longer periods. Far from all marinas are staffed, and also, the owner of the watercraft does in most cases not live nearby. Thus, it can take days, weeks or even months before the watercraft is checked. When docked, the watercraft will be subjected to sometimes very harsh weather conditions with changes in water level and strong forces caused by wind and waves. It is not uncommon that there are problems with damages to the watercraft's boat hull due to insufficient mooring and even that the watercraft floats away.

There is thus a need for a remote surveillance system that can give input to the owner of the watercraft or to the marina regarding the position and movement of the boat hull also after docking. Summary

One object of the present invention is to provide a method and an apparatus that allows a remote surveillance of a watercraft and its boat hull after docking.

Another object of the invention is to provide a method and an apparatus that can be used by a marina, the owner of a dock or the owner of the watercraft.

The method and apparatus should be applicable to all types of watercrafts no matter if the identification of the watercraft is known or not.

The method and apparatus should be applicable no matter if it is a dock providing a jetty with slips or a mooring adjacent a jetty or even a natural harbor.

As yet another object, the method and apparatus should be able to be easily integrated in a booking or subscription system handled by a marina.

These and other objects are solved by a method for detecting abnormal movements of a boat hull in a dock, the method comprising the steps of: from a fixed position of the dock, dynamically monitoring a position of a boat hull by using a fixedly arranged sensor; checking if the dynamically monitored position of the boat hull, as compared to a known effective surveillance area of the sensor, falls within a preset acceptable interval, and if determined to deviate from said preset acceptable interval, generate a notification.

A dock is typically located in an area that is provided with wave breakers providing a reduced seaway. Should the dock instead be a natural harbor this is typically located in an area that offers natural lee, such as in a bay. Also, a moored boat hull will constantly move due to outer conditions caused by water movements and wind conditions. This movement of a properly moored boat hull will typically, when monitored, be recognized as a cyclic sinus wave pattern corresponding to that of the water. The term "abnormal movements" should in the context of the invention be understood as movements of the boat hull that differs from such regular, sinus waved movement pattern of a moored boat hull.

The term "dock' should in the context of the invention be understood as a place where a watercraft is moored, typically at a jetty or a pier. In its simplest form the dock can be a natural harbor. The jetty can be provided with optional slips. The dock has a longitudinal extension and a transverse direction.

In the context of the invention, the term "longitudinal' is to be understood as the direction substantially perpendicular to the extension of the jetty. Also, in the context of the invention the term "transverse" is to be understood as the direction substantially in parallel to the extension of the jetty.

The term "effective surveillance area" should in the context of the invention be understood as the surveillance area of the sensor where the sensor is determined to provide sensor data of reliable quality. The surveillance area can be defined by sensor data pertained from one or more sensors. It is to be understood that depending on the type of sensor or sensors, the effective surveillance area may be two-dimensional (plane) or three-dimensional (volume).

The underlying idea of the invention is that as long as a watercraft is in the water, its boat hull will constantly move due to outer conditions caused by water movements and wind conditions. This applies also when the watercraft is properly moored at a dock. By dynamically monitoring the position of the boat hull from a fixed position, and comparing the position with the fixed boundaries of the dock, it can be determined if there are any abnormal movements that should trigger an action, such as a maintenance of an insufficient or failed mooring. The frequency of the checking, i.e. the sampling frequency, can be fixed or be set depending on e.g. weather forecast. If the weather forecast predicts strong wind or high water levels, the sampling frequency can be increased. Since the dynamic monitoring is made from a fixed position, the method is applicable no matter if the watercraft is previously known or not. Thereby there is no need for any equipment being installed onboard the watercraft in order for the method to work. Accordingly, any watercraft approaching a marina or a dock provided with the system may be monitored.

Since the dynamic monitoring is made from a fixed position, information will dynamically be provided if the dock is occupied or available. Thus, in a very simple form, the method may be used to determine if the dock is available or not, i.e. is there a boat docked or not. This information can be transmitted to be used in a booking system to thereby allow increased revenues to the marina. Increased revenues may by way of example be made possible by offering non-occupied but rented docks to temporary guests.

The method may further comprise the step of determining, by using the sensor, sensor data pertaining to the volumetric boundaries of the boat hull, and wherein said sensor data is used when dynamically monitoring the position of the boat hull.

By determining the volumetric boundary of the boat hull, a virtual body representing the outer dimensions of at least a portion of the boat hull will be generated. Since the sensor is fixed at the dock the sensor data pertaining to the volumetric boundaries will represent a portion of the boat hull that is arranged in the known effective surveillance area. The represented portion will typically correspond to the either the fore portion or the aft portion of the boat hull depending on how the watercraft is moored. Also, if a boat is moored with its long side along a jetty, two or more adjacent sensors may be used to determine available remaining space along the jetty, thereby allowing a better degree of capacity utilization with more boats mooring. Since both ends of a boat hull in most cases can be seen as slightly arrow shaped, the sensor data pertaining to the volumetric boundary will represent a substantial portion of either the fore portion or the aft portion of the boat hull. By dynamically monitoring the movements of that virtual body inside the known effective surveillance area of the sensor, it may be possible to detect any abnormal movements of the boat hull.

Each boat type and boat model has its own design whereby the pertained sensor data can be used to provide a rough identification of the monitored boat hull. Provided the method is arranged to cooperate with a booking system, this identification may be used to handle a subscription of the dock or payment. By way of example, if a first watercraft is entitled to use a specific dock, sensor data pertaining to the volumetric boundaries of the boat hull of that first watercraft may be stored in a memory. If a second watercraft moors the same dock, sensor data pertaining to the volumetric boundaries of the boat hull of the second watercraft may be compared to that of the first watercraft. Predetermined rules may determine if such mooring should be allowed or not. If allowed, it could trigger a notification relating to payment or information to the operator of the second watercraft to find another dock.

The method may further comprise the step of, based on the sensor data pertaining to the volumetric boundaries of the boat hull, determine a center line of the boat hull, and wherein a relative position between the determined center line of the boat hull and the known effective surveillance area of the sensor is used when checking if the dynamically monitored position of the boat hull deviates from the preset acceptable interval.

By comparing the relative position between the determined center line and the known effective surveillance area of the sensor it may be possible to detect any abnormal side ward or angular movements of the boat hull. A deviation may indicate a failure of the mooring at either the aft or the fore or both at the aft and the fore.

The step of checking may comprise the step of checking if the dynamically monitored position of the boat hull, as compared to the known effective surveillance area of the sensor, falls within a preset acceptable lateral deviation, and if determined to deviate from said preset acceptable lateral deviation, generate the notification.

The term "lateraf is in the context of the invention to be understood as the transverse direction of the dock. Accordingly, by checking any deviation from the preset acceptable lateral deviation, the movement of the boat hull inside the dock may be monitored. If the lateral deviation is determined to be too large, the notification may indicate or suggest to the receiver of the notification that a fender should be mounted or that the mooring should be strengthened. A lateral deviation can also include any angular deviation since that would imply that either the fore or the aft has an insufficient mooring allowing the boat hull to move in the lateral direction.

The step of checking may comprise checking if the dynamically monitored position of the volumetric boundaries of the boat hull, as compared with the fixed position of the sensor, falls within a preset acceptable vertical deviation between the fixed position of the sensor and the volumetric boundaries of the boat hull, and if determined to deviate from said preset acceptable vertical deviation, generate the notification.

By checking any deviation from the preset acceptable vertical deviation, the movement of the boat hull relative the fixed position of the sensor may be monitored. If the vertical distance is determined to be deviate too much this may indicate abnormal changes in the water stand or even leakage/sinking. A sudden vertical deviation, i.e. a peak, may be an indication of a non-authorized person having entered the watercraft.

The step of checking may comprise checking if the dynamically monitored position of the boat hull, as compared to a fixed front boundary represented by the fixed position of the dock, falls within a preset acceptable longitudinal deviation, and if determined to deviate from said preset acceptable longitudinal deviation, generate the notification. By checking any deviation from the preset acceptable longitudinal deviation, the movement of the boat hull back and forth relative the fixed position of the sensor, which as such represents the position of the jetty may be monitored. If the longitudinal deviation is determined to be deviate too much this may indicate an insufficient mooring.

The sensor may be an image sensor and the boat hull may comprise at least one fixed reference point, and the step of checking may comprise checking if the dynamically monitored position of the boat hull with its at least one fixed reference point, as compared to the fixed position of the dock, falls within any of a preset acceptable lateral, longitudinal or vertical deviation, and if determined to deviate from any of said preset acceptable lateral, longitudinal or vertical deviations, generate the notification. The checking of the lateral, longitudinal or vertical deviation of the fixed reference points on the boat hull in view of the fixed position of the dock may be made by image analysis. The method may further comprise transmitting the notification to an external receiver. The receiver may by way of example be the boat owner, the marina, a supervisor of the area or a surveillance company. The notification may be transmitted wireless, e.g. as an e-mail, a telephone message or a text message. The notification may also be audial, i.e. a siren.

The sensor may be an IR sensor, an ultrasound sensor, a laser sensor, an image sensor such as a camera or a radar sensor, such as a micro radar. It is to be understood that also other sensors may be applicable to serve the same purpose. One or more sensor may be used. In case of more than one sensor, these may together define the effective surveillance area.

According to another aspect, the invention refers to an apparatus for detecting abnormal movements of a boat hull in a dock, the apparatus being configured to be fixedly mounted to a dock, wherein the device comprises:

a sensor configured to dynamically monitor a position of the boat hull; and a processor configured to check if the dynamically monitored position of the boat hull, as compared to a known effective surveillance area of the sensor, falls within a preset acceptable interval, and if determined to deviate from said preset acceptable interval, generate a notification.

The features and the technical effects related thereto have previously been discussed above in view of the method. The advantages apply equally well to the apparatus. To avoid undue repetition, reference is made to the sections above discussing the method.

The apparatus may further comprise a memory configured to store the data pertaining to the known effective surveillance area of the sensor. It is to be understood that also other types of information may be stored. Non-limiting examples are sampling frequency and information relating to receivers of notifications.

The apparatus may further comprise a transmitter. Alternatively, the apparatus may comprise a transceiver. No matter if the apparatus comprises a transmitter or a transceiver, this can be wirelessly operating.

Further objects and advantages of the present invention will be obvious to a person skilled in the art reading the detailed description given below describing different embodiments.

Brief description of the drawings

The invention will be described in detail with reference to the schematic drawings. Fig. 1 discloses highly schematically a dock with a fixed sensor and a moored watercraft.

Figs. 2a-2c disclose examples of different patterns when using more than one sensor.

Fig. 3 is a flowchart representing the method.

Figs. 4a-4d are schematic views of different deviations.

Fig. 5 discloses an alternative method of determining different deviations.

Detailed description

Now turning to Fig. 1 , one embodiment of a dock 1 with a moored watercraft

2 is disclosed. The dock 1 is schematically disclosed as being arranged in connection to a jetty 3 from which two optional slips 4 extend. The jetty 3 represents a substantially fixed position in view of the moored watercraft 2. The watercraft 2 which as such will move along with the inherent natural movements of the water within the restrictions provided by the moorings 5. In the illustrated example the watercraft is moored to the jetty 3 at its fore and to a buoy 6 at its aft.

The dock 1 has a longitudinal extension Y and a transverse extension X. The dock 1 also has a vertical extension V. In the context of the invention, the term "longitudinaf is to be understood as the direction substantially perpendicular to the extension of the jetty 3. Also, in the context of the invention the term "transverse" is to be understood as the direction substantially in parallel to the extension of the jetty 3.

The watercraft 2 has a boat hull 7 having a fore 7a and an aft 7b. The watercraft 2 has a geometrical centerline GCL extending from the fore 7a to the aft 7b. The boat hull 7 is mirror symmetric around said geometrical centerline GCL. The fore 7a and the aft 7b do each have an arrow-shaped profile. The watercraft 2 is disclosed as being moored with the fore 7a facing the jetty 3. The watercraft 2 may also be moored with e.g. the fore 7a facing the jetty 3.

An apparatus 10 is fixedly mounted to the dock 1 . The mounting may by way of example be made by bolting to the jetty 3. It is preferred that the apparatus 10 is removably mounted. Thereby the apparatus 10 may be removed during wintertime or when not in use. The apparatus 10 may be portable. Thereby the apparatus 10 may be brought along with the watercraft 2 and be arranged on land when mooring the watercraft 2 in a natural harbor.

The apparatus 10 may be contained in a housing 1 1 . The housing 1 1 forms a protective casing. It is preferred that the apparatus 10 is mounted to the dock 1 in a position substantially corresponding to the longitudinal centerline of the dock 1 . In case of a natural harbor it is preferred that the apparatus 10 is arranged on the land in such position that the geometrical centerline GCL of the watercraft 2 when moored is essentially aligned with a virtual line extending between the apparatus 10 and a buoy to which the watercraft is moored. It is to be understood that when mooring to a natural harbor a visual estimate applies.

The apparatus 10 may be wired, i.e. connected to a fixed power supply. Alternatively, the apparatus 10 may be wireless and instead be provided with a battery. The battery may be connected to a solar panel to allow charging by using solar energy.

The apparatus 10 comprises a sensor 12. The sensor 12 is configured to dynamically monitor the position of the boat hull 7 in the dock 1 .

The sensor 12 may be an IR sensor, an ultrasound sensor, a laser sensor, an image sensor such as a camera or a radar sensor, such as a micro radar. It is to be understood that also other sensors may be applicable to serve the same purpose. The sensor 12 has a known effective surveillance area 13. The effective surveillance area 13 is schematically disclosed as a hashed area in Fig 1 . It is to be understood that depending on the type of sensor 12 or sensors, the effective surveillance area may be essentially two-dimensional or three-dimensional. By way of example, a radar sensor may provide a substantially conical surveillance area.

One or more sensors 12 may be used. In the case of more than two sensors

12, the individual sensors 12 may be arranged along a line, see Fig 2a or in an array, see Fig.2b. The plurality of sensors 12 may together define a known effective surveillance area 13. In case of more than one sensor 12, the sensors 12 may be of different types.

The one or more sensors 12 may be arranged to project in a direction perpendicularly away from the jetty 3. Alternatively, the one or more sensors 12 may be arranged to project at an angle a from the jetty 3, see Fig. 2c. In case of several sensors 12, each sensor 12 may have a unique angle to the jetty 3. The total effective surveillance area 13' will be defined by the overlap of the effective surveillance areas 13 of the individual sensors 12.

The one or more sensors 12 may be arranged above water level or below water level. The position chosen depends on the type of sensor. Also, it is to be understood that one senor may be arranged above water level and one sensor may be arranged below water level.

The schematically disclosed sensor 12 in Fig. 1 is an ultrasound sensor which is oriented in a direction perpendicularly away from the jetty 3. The ultrasound sensor has a three-dimensional effective surveillance area 13 that represents a cone. It is to be stressed that the same principle applies to a radar sensor.

In case the sensor 12 is an image sensor, the watercraft 2 may be provided with at least one fixed reference points 20. The fixed reference points may be provided by stickers, see Fig. 4d.

The apparatus 10 further comprises a processor 14. The processor 14 may by way of example be provided by a small computer. The processor 14 is configured to communicate with the sensor 12. In case of several sensors 12, the processor 14 is configured to communicate with the plurality of sensors 12. The processor 14 is configured to check if the dynamically monitored position of the boat hull 7, as compared to the known effective surveillance area 13 of the sensor 12, falls within a preset acceptable interval. If the dynamically monitored position is determined to deviate from said preset acceptable interval, the processor 14 is configured to generate a notification.

The apparatus 10 may comprise a transmitter 17. Alternatively, the apparatus may comprise a transceiver. No matter if the apparatus comprises a transmitter or a transceiver, this can be wirelessly operating. The notification may be transmitted to an external receiver 15. The external receiver 15 may by way of example be the boat owner, a marina, a supervisor of the marina or a surveillance company. The notification may be transmitted wirelessly, e.g. as an e-mail, a telephone message or a text message. The notification may also be an audial signal or include an audial signal.

The sampling frequency, i.e. the frequency at which the checking is made, may be fixed. In one embodiment, the processor 14 may allow the sampling frequency to be changed. The sampling frequency may be changed automatically based on detected abnormalities. The sampling frequency may be remotely changed by the operator based on a received notification.

The transmitter 17 or transceiver may be configured to communicate with additional sensors 16. Non-limiting examples of such additional sensors are magnetic switches forming part of a theft alarm mounted onboard the watercraft 2.

The additional sensors 16 may by way of example be mounted adjacent a door or a hatch.

The apparatus may further comprise a memory 18. The memory 18 may be configured to store data pertaining to the known effective surveillance area 13 of the sensor 12. The memory 18 may also store other data. Non-limiting examples are sampling frequency and information relating to receivers 15. Now turning to Figs. 1 and 3, the method for detecting abnormal movements of a boat hull 7 in a dock 1 will be described. The execution of the method prescribes that an apparatus 10 of the above type has been fixedly mounted to the dock 1 .

The method comprises:

Dynamically monitor, step 100, from a fixed position of the dock 1 , a position of a boat hull 7 by using a fixedly arranged sensor 12. The information from the sensor 12 may be transmitted by the transmitter 17 or the transceiver to the processor 14. Alternatively, CAM-bus technology may be used. The information from the sensor may, depending on the type of sensor, be light, sound or a radar signal which is reflected by the hull and detected by the sensor 12.

Determining, step 200, by using the sensor 12, sensor data pertaining to the volumetric boundaries VB of the boat hull 7. The volumetric boundaries may by way of example be determined by studying the time for the outgoing signal to be reflected back to the sensor or determining energy content in the reflected signal. The pertained sensor data is used when dynamically monitoring the position of the boat hull 7.

The sensor 12 will be able to detect a watercraft 2 already when its boat hull 7 enters the effective surveillance area 13 of the sensor 12. The sensor 12 will dynamically monitor the boat hull 7 as long as the boat hull 7 remains inside the known effective surveillance area 13 of the sensor 12. Since the apparatus with the sensor 12 is fixedly arranged to the dock 1 , the sensor 12 will dynamically monitor the relative movement of boat hull 7 relative to the known effective surveillance area 13 of the sensor 12.

In case the sensor 12 is an image sensor, the fore 7a and/or the aft 7b of the watercraft 2 may be provided with at least one fixed reference point 20. Since the apparatus with the sensor 12 is fixedly arranged to the dock 1 , the processor 14 will be able to dynamically determine the movements of the boat hull 7 by determining the movements of the fixed reference points 20 relative to the fixed position of the sensor 12.

Checking, step 300, if the dynamically monitored position of the boat hull, as compared to the known effective surveillance area of the sensor, falls within a preset acceptable interval.

If it is determined that there is no deviation, steps 100 to 300 are repeated. If a deviation from said preset acceptable interval is determined, a notification is generated, step 400. The notification can be transmitted to an external receiver 15. The receiver 15 may be by way of example, the boat owner, the marina, a supervisor of the area or a surveillance company. The notification may be transmitted wirelessly, e.g. as an e-mail, a telephone message or a text message. The notification may comprise information to the receiver 15 describing the type of detected deviation. The notification may also be audial.

After finishing step 400, the method of steps 100 to 300 are repeated.

According to step 200, the pertained sensor data is used when dynamically monitoring the position of the boat hull 7. In the case where the sensor 12 is an ultrasound sensor or a radar sensor, such as a micro radar, the sensor 12 will be able to provide sensor data pertaining to a three-dimensional virtual body

representing the outer boundaries of the part of the boat hull 7 that is momentarily arranged within the known effective surveillance area 13 of the sensor 12. Based on this information the volumetric boundary VB of the boat hull 7 may be determined. The represented portion of the boat hull 7 will typically correspond to the either a portion of the fore 7a or a portion of the aft 7b, depending on how the watercraft 2 is docked. Since both ends of a boat hull 7 in most cases can be seen as being slightly arrow-shaped, the sensor data pertaining to the volumetric boundary VB of the boat hull 7 will represent a substantial portion of either the fore 7a or the aft 7b. By dynamically monitoring the movements of that virtual body inside the known effective surveillance area 13 of the sensor 12, it may be possible to detect any abnormal movements of the boat hull 7.

The same principle is applicable if a boat is moored with its long side along a jetty. In that case two or more sensors may be arranged along the jetty on a known distance from each other. Depending on how many of the sensors that detect presence of a boat hull it may be determined if an individual sensor detects a fore, an aft or a long side. Based on this information, available remaining space along the jetty may be determined. It allows by way of example that boats may be docked side by side along the jetty with different orientations.

Further, each boat model has its own design. Thereby the pertained sensor data can be used to provide a rough identification of the monitored watercraft. This information can be stored in the memory. Depending on type of sensor used, the sensor may determine not only the volumetric boundary but also the type of material, such as metal, plastic or composite. The type of material may be used as yet another parameter to identify the monitored watercraft. Provided the method is applied to communicate with and share information with a booking system, this identification may be used to handle a subscription of the dock 1 or payment. By way of example, if a first watercraft is entitled to use a specific dock, sensor data pertaining to the volumetric boundaries VB of the boat hull of that first watercraft may be stored in the memory. If a second watercraft moors the same dock, sensor data pertaining to the volumetric boundaries VB of the boat hull of the second watercraft may be compared to that of the first watercraft. If a difference in the pertained sensor data relating to the first and second watercrafts is determined, this is an indication that the two watercrafts represent different models. Predetermined rules may determine if mooring should be allowed or not, and if allowed, it could trigger a notification relating to payment or information to the operator of the second watercraft.

In one embodiment, the method may comprise the step of, based on the sensor data pertaining to the volumetric boundaries VB of the boat hull 7, determine by calculation a virtual center line of the boat hull VCL. It is to be understood that not the full width of the boat hull 7 must be arranged inside the known effective surveillance area 13 of the sensor 12. It is possible to determine a virtual centerline VCL of the boat hull 7 also if only a part of the boat hull 7 as seen in its width direction is arranged inside the known effective surveillance area 13. This is made possible since a boat hull 7 is mirror symmetric along its geometrical centerline GCL. The relative position between the determined virtual center line VCL of the boat hull 7 and the known effective surveillance area 13 of the sensor 12 may be used when checking if the dynamically monitored position of the boat hull 7 deviates from the preset acceptable interval. A deviation may indicate a failure of the mooring at either the aft 7b or the fore 7a or both at the aft and the fore.

Turning to Fig. 4a, the processor 14 may be configured to indicate a lateral deviation ΔΧ of the boat hull 7, i.e. in the transverse direction, when moored in a dock 1 . This is made by checking if the dynamically monitored position of the boat hull 7, as compared to the known effective surveillance area 13 of the sensor 12, falls within a preset acceptable lateral deviation. If it is determined that there is a lateral deviation ΔΧ from said preset acceptable lateral deviation, a notification may be generated.

The known effective surveillance area 13 provided by the sensor 12 has a known centerline A. The determined virtual centerline VCL of the virtual body represented by the volumetric boundaries VB of the boat hull 7 is illustrated by line VCL. The lateral deviation ΔΧ is determined as the lateral distance between line A and line VCL. If the determined lateral deviation ΔΧ exceeds a preset acceptable lateral deviation, a notification may be generated. The system may be provided with an inherent inertia. By way of example, for a notification to be generated, the preset acceptable lateral deviation must have been determined to be exceeded a certain number of times during a preset period of time.

An issued notification may indicate or suggest to the receiver that a fender is recommended to be mounted or that the mooring should be strengthened. Turning to Fig. 4b, the processor 14 may be configured to indicate a vertical deviation ΔΖ. This may be made by checking if the dynamically monitored position of the volumetric boundaries VB of the boat hull 7, as compared to the fixed position of the sensor 12, falls within a preset acceptable vertical deviation ΔΖ between the fixed position of the sensor 12 and the volumetric boundaries VB of the boat hull 7. If it is determined that there is a deviation from said preset acceptable vertical deviation ΔΖ, a notification may be generated.

This may by way of example be made by determining by calculation the center of mass CM for the virtual body represented by the volumetric boundaries VB of the boat hull 7. The known effective surveillance area 13 provided by the sensor 12 has a known centerline A having a known vertical position. The lateral deviation ΔΖ is determined as the vertical distance between line A and the center of mass CM. If the determined vertical deviation ΔΖ exceeds a preset acceptable vertical deviation, a notification may be generated. The system may be provided with an inherent inertia. By way of example, for a notification to be generated, the preset acceptable lateral deviation must have been exceeded a certain number of times during a preset period of time.

A vertical deviation ΔΖ may indicate that the boat hull 7 is leaking and that the boat hull 7 thereby changes it position in view of the sensor 12. It can also be an indication of an abnormal change in the water stand. A detected sudden vertical deviation ΔΖ, which can be seen as a peak value, may be an indication that a non- authorized person has entered the watercraft. A peak value may by way of example trigger an immediate audial alert, activation of a surveillance camera or a notification to a receiver.

Turning to Fig. 4c, the processor 14 may be configured to indicate a longitudinal deviation ΔΥ of the boat hull 7 when moored in a dock 1. This may be made by checking if the dynamically monitored position of the boat hull 7, as compared to a fixed front boundary represented by the fixed position of the dock 1 , falls within a preset acceptable longitudinal deviation ΔΥ. If it is determined that there is a deviation from said preset acceptable longitudinal deviation, a notification may be generated.

The known fixed front boundary of the dock is represented by the fixed position of the dock 1 . This fixed position is illustrated as point B. Also, the foremost detected point of the virtual body represented by the volumetric boundaries VB of the boat hull 7 is illustrated by point C. The longitudinal deviation ΔΥ is determined as the longitudinal distance between the fixed point B and foremost point C. If the determined longitudinal deviation ΔΥ exceeds a preset acceptable longitudinal deviation, a notification may be generated. The system may be provided with an inherent inertia. By way of example, for a notification to be generated, the preset acceptable lateral deviation must have been exceeded a certain number of times during a preset period.

By checking any deviation from the preset acceptable longitudinal deviation

ΔΥ, the movement of the boat hull 7 back and forth relative the jetty 3 may be monitored. If the longitudinal deviation ΔΥ is determined to be deviate too much this may indicate an insufficient mooring. An issued notification may indicate or suggest to the receiver that a fender is recommended to be mounted or that the mooring should be strengthened.

Now turning to Fig. 4d, one embodiment is disclosed wherein the boat hull 7 is provided with at least one fixed reference point 20. The fixed reference points 20 may be provided by e.g. stickers arranged on the boat hull 7 in its fore 7a and/or aft 7b. In this embodiment the sensor 12 is an image sensor. By using the sensor 12, the position of the boat hull 7 with its at least one fixed reference point 20 is dynamically monitored. The dynamically monitored position of the boat hull 7 with its at least one fixed reference point 20 is checked as compared to the fixed position of the dock 1 . If it is determined that any of the lateral, longitudinal or vertical deviations ΔΧ, ΔΥ, ΔΖ of the at least one fixed reference point deviates from any of said preset acceptable lateral, longitudinal or vertical deviations, a notification is generated. The checking of the lateral, longitudinal or vertical deviations of the at least one fixed reference point 20 may be made by the processor using image analysis.

It is to be understood that the lateral deviation ΔΧ, the vertical deviation ΔΖ and the longitudinal deviation ΔΥ may be determined in a number of ways. The examples provided by Figs. 4a-4c are to be seen as non-limiting examples. The same principle may be applied to determine an angular displacement.

As an alternative to determining the lateral deviation ΔΧ, the longitudinal deviation ΔΥ and the vertical deviation ΔΖ, the information relating to the determined volumetric boundaries VB may be used, see Fig. 5. When using a radar sensor, such as a micro radar, the information relating to the volumetric boundaries VB may be seen as an imaginary body representing reflected energy content for a high number of virtual points in the volume. The virtual points may be seen as a virtual cloud. Since the sensor 12 has a fixed position, each virtual point will have a known position in the space, i.e. its x _n , y _n and z _n coordinates will be known, "n" represents identification number of an individual virtual point. Accordingly, a movement of the hull will be represented by a corresponding movement of the imaginary body, which movement may be determined with a high degree of certainty by using the processor 14. By comparing the momentary position of the imaginary body representing the volumetric boundary VB with e.g. the known position of the jetty 3 and any slips, it is made possible to determine if the lateral, longitudinal and vertical deviations ΔΧ, ΔΥ and ΔΖ are within preset acceptable deviations or not. If the determined deviations exceed preset acceptable deviations, a notification may be generated. The system may be provided with an inherent inertia. By way of example, for a notification to be generated, the preset acceptable deviations must have been exceeded a certain number of times during a preset period of time.

No matter method, it is to be understood that if there is an insufficient mooring it is likely that notifications relating to abnormal movements in more than one direction are likely to be issued.

The frequency of the checking may be set depending on e.g. weather forecast. If the weather forecast predicts strong wind or high water levels, the sampling frequency can be increased.

Since the dynamic monitoring is made from a fixed position, the method is applicable no matter if the watercraft is previously known or not. Thereby there is no need for any equipment being installed onboard the watercraft in order for the method to work. Accordingly, any watercraft approaching a marina or a dock provided with the system may be monitored.

Since the dynamic monitoring is made from a fixed position, information will dynamically be provided if the dock is occupied or available. This information can be used in a booking system to thereby allow increased revenues to the marina by offering sublease.

The apparatus may be provided with lamps or other types of information carriers, such as arrows. The information carriers may provide information to a watercraft approaching the jetty regarding availability of the dock. The information carriers may also help navigation into the dock.

Further, the apparatus may comprise a loud-speaker allowing the provision of an audial signal.

The apparatus may use CAM-bus technology.

The apparatus may be arranged to determine deviations by using quantities like speed and accelerations.

The method and apparatus may be used to assist during docking by providing information to the driver about distance to the jetty and to any slips. The apparatus may be configured to communicate with e.g. assisting navigation lamps on the jetty and/or slips.