Inland river bridge district Shipborne navigation is collision avoidance system and collision prevention method initiatively
Technical field
Patent of the present invention relates to a kind of Shipborne navigation collision avoidance system and collision prevention method.
Background technology
Bridge is as the tie of linking up land communications transport between two sides, river, and its importance and functions is self-evident.Along with the fast development of China's communications and transportation cause, bridge is built more and more, also builds closeer and closeer.Only 7 bridge blocks on the Changjiang river before last century the nineties, to this century only Yibin, the Changjiang river section just to have more than 60 built or the building Yangtze Bridge to entrance of Changjiang River, building up and going into operation on the one hand for land communications transport provides huge facility of these bridges, facilitates people's life and facilitates Regional Economic Development; On the other hand because bridge is to the restriction of navigation environment, become the navigation bottleneck of inland water transport gradually, once there is bridge collision in Qiao Qu waters, causing damage to bridge, while cutting off road traffic, also can occluding surface traffic, between the boats and ships of Qiao Qu waters, collision accident also very easily causes navigation channel to block up simultaneously.Therefore, be ensure bridge, bridge district navigation safety, need to design a kind of active anticollision device when navigate by water in inland river bridge district for deck officer, help driver safety navigates by water, and is a problem needing solution badly.
One, invention demand
The needs of Bridge 1 beam manager
Present stage, bridge management policy, to bridge pier anticollision, is all adopt various passive collision prevention measure.As installed anticollision barrier and so in bridge pier periphery.Although but take various passive collision prevention measure, boats and ships can only be reduced at collision bridge pier, the loss caused after namely having caused the vessel bump bridge fact as far as possible.First can not fundamentally avoid or reduce the number of times of ship collision bridge pier, secondly also cannot predict the consequence of ship collision bridge pier.
Therefore, from the angle of bridge management side, when vessel traffic flow is day by day busy, needs a kind of active anticollision device when bridge district water-area navigation is installed on ship panel, initiatively dodge bridge pier from the angle of marine operation safety, reduce vessel bump bridge probability.Ensure bridge security.
The needs of 2 deck officers
Inland navigation craft bridge has all been installed radar, sounder, AIS etc. and has been helped navigator.Driver can help navigator to understand navigation environment information around boats and ships by these, comprises radar and sweeps object relative orientation information near the boats and ships that measure, the basic sail information of neighbouring boats and ships that the ship's navigation Water Depth Information that sounder obtains and AIS obtain.
These help navigator all can only provide environmental information around boats and ships for driver, can do nothing to help driver and judge the sailing situation around boats and ships.Although the improvement in the building of various hydraulic engineering, navigation channel, navigation condition has had and has significantly improved, and expanding economy also brings the more crypto set of traffic flow, simultaneously the navigation channel of supervising as emphasis, bridge district, and boats and ships behavior is restricted more.
Therefore, when navigating by water in bridge district, driver needs a kind of anticollision device of active, assists it to judge the security postures of ship's navigation, after differentiating, provides the sailing method of suggestion to the contingent accident of this ship, helps the safe navigation of driver in inland river bridge district.
The needs of 3 maritime administration departments
Bridge is huge to local economic development effect, and simultaneously along with the fast development of inland water transport industry, vessel traffic current density becomes large, and the safety in Qiao Qu waters becomes quite sensitive and important.Qiao Qu waters, once there is analysis of vessel traffic accidents, if there is ship foul or stranded, then may cause navigation channel to block up; If ship collision navigation mark, navigation mark can allow rear ship cannot judge Qiao Qu air route and then cause accident after losing; If ship collision bridge pier, causing the injury that cannot remedy to bridge pier, while reducing bridge serviceable life, be also more prone to cause boats and ships to block up.
Because of the importance of inland river bridge district waters traffic safety, the task of supervision of maritime administration department is very heavy.Usual maritime administration department obtains supervising the vessel traffic stream information of the water surface by VTS or radar, and manages ship's navigation according to these transport information, work strain and uninteresting, once absent-mindedness, maritime accidents forecast may occur.
Therefore, maritime administration department needs to install a kind of boats and ships initiatively anticollision device at ship panel, to alleviate work load, improves supervisory efficiency.Once this device finds that this ship has accident risk, then inform supervision department by wireless communication module; The suggestion sailing method of this ship also can be informed driver by this device simultaneously, assists driver's navigation.
Two, spot ship collision prevention equipment status
1 automatic radar plotting aid
Automatic radar plotting aid (Automatic Radar Plotting Aid, ARPA) can manually or automatic capturing radar sweep and survey target automatically track target, on radar screen, show course and the speed of a ship or plane of tracking target with vector form simultaneously.Meanwhile, when the time of the distance to closest point of approach and arrival distance to closest point of approach that calculate target is less than set permission boundary, can automatically to report to the police to remind driver to take measures to keep clear.
But in waters, inland river bridge district, because bridge is to the bridging effect of radar signal, radar sweeps that to survey distorted signals phenomenon serious, the target for pier location and bridge rear cannot reach sweeps survey effect, and especially at sleety weather, radar sweeps that to survey effect poorer.
2AIS collision avoidance instrument
AIS collision avoidance instrument adds collision prevention module on the basis of common AIS.Its collision prevention principle is substantially the same with automatic radar plotting aid, by accepting the AIS information of boats and ships around, calculating the time of distance to closest point of approach and arrival distance to closest point of approach, utilizing report to the police to remind driver to take measures to keep clear when being less than set boundary.
But adopt GPS locating module in AIS, itself exists positioning error, ais signal is unstable simultaneously easily loses.
Visible, realize the active homing of inland river bridge district boats and ships, existing inland navigation craft helps navigator mainly to there is following problem:
(1) relative position of inland river bridge district scope bridge pier, navigation mark, around ship and this ship cannot accurately be judged.
(2) calculate by means of only simple distance to closest point of approach and arrival distance to closest point of approach, not for the movement tendency of boats and ships, the security postures of navigation is judged in advance;
(3) a kind of ship-borne equipment that initiatively can realize preventing collision method prompting to driver is not had.
Summary of the invention
The technical problem to be solved in the present invention is: provide inland river bridge district Shipborne navigation initiatively collision avoidance system and collision prevention method, by realizing the prediction to ship's navigation situation, solving spot ship and helping navigator accurately cannot obtain collision prevention object position, the defect of anticipation cannot be carried out more accurately to distance to closest point of approach and arrival distance to closest point of approach.
The present invention for solving the problems of the technologies described above taked technical scheme is: inland river bridge district Shipborne navigation is collision prevention method initiatively, it is characterized in that: it comprises the following steps:
Step one, data acquisition:
Gather hydrographic information and weather information, hydrographic information comprises water level, water flow velocity and current direction; Weather information comprises wind speed and direction;
The ship information of boats and ships near being received by watercraft AIS equipment, received the ship information of this ship by watercraft AIS equipment, GPS device, ship information comprises accommodation, the speed of a ship or plane, course information; Described neighbouring boats and ships are all boats and ships that AIS equipment can receive;
Gather navigation channel base attribute information, and automatic on-line upgrades river figure information;
Step 2, data store:
Data step one gathered store;
Step 3, Trajectory Prediction: in conjunction with real-time hydrographic information and weather information, according to the ship information of this ship with his ship, the flight path of this ship and his ship is predicted, obtains the flight path information of every ship, specifically comprise:
3.1, accommodation variation prediction: according to the variation tendency at history accommodation, utilizes the situation of change of third index flatness to accommodation to predict, obtains the position prediction value of boats and ships, i.e. the predicted value of longitude and latitude;
3.2, ship motion prediction: utilize the change trend of third index flatness to speed of the ship in metres per second, course to predict, and then in conjunction with the current accommodation of these boats and ships, the speed of a ship or plane, course, flight path is predicted, then utilize hydrographic information and the drift impact that causes of weather information on this ship track to revise, obtain the position prediction value of boats and ships;
3.3, integrated forecasting: introduce confidence parameter, accommodation variation prediction and ship motion are predicted the position prediction value at the accommodation that two kinds of methods obtain considers, finally obtain flight path information accurately; Flight path information is made up of future position, and the information of future position comprises longitude predicted value, latitude predicted value and time;
Step 4, distance to closest point of approach calculate: the flight path information obtained by step 3, calculate distance to closest point of approach and the time to closest point of approach of this ship and object, specifically comprise:
4.1, be sequence by the future position in this ship and object flight path information with time, successively the pseudo-prediction distance between this ship and the future position of object is calculated, when the monotonicity of pseudo-prediction distance to become from successively decreasing increase progressively time, obtain this ship of pseudo-distance to closest point of approach and correspondence and the future position of object;
4.2, be as the criterion with the information of this ship future position corresponding to pseudo-distance to closest point of approach, choose several this ship future positions before and after this this ship future position, the future position information of method of interpolation to object is utilized to carry out time synchronizing, calculate the real prediction distance of this ship corresponding to this ship future position and object, when the monotonicity of prediction distance to become from successively decreasing increase progressively time, obtain the distance to closest point of approach of future position and this ship future position of correspondence; Before and after this selected this ship future position, the number of this ship future position is limited to find the distance to closest point of approach of future position;
4.3, be as the criterion with the information of this ship future position corresponding to the distance to closest point of approach of future position, using 1 second as the time interval, utilize method of interpolation, obtain the real prediction distance of this ship before and after this this ship future position in the some time and object, when the monotonicity of prediction distance to become from successively decreasing increase progressively time, obtain distance to closest point of approach and the time to closest point of approach of this definite ship and object; The length of this selected this ship future position surrounding time is limited with the distance to closest point of approach of object to obtain this definite ship;
Object is the one in he ship, bridge pier or navigation mark, when object be bridge pier or navigation mark time, the speed that is considered as by object is his ship of 0;
Step 5, collision accident early warning are advised with active collision prevention:
Respectively according to the dimension information of this ship with different target thing, preset the distance threshold values between this ship and different target thing, according to the distance to closest point of approach of this ship with object, size between the distance threshold values judging its distance to closest point of approach and setting, if be less than threshold values, send space danger alarm signal, simultaneously according to the size cases of distance to closest point of approach, provide the active collision prevention suggestion of ship turning;
According to the time to closest point of approach of this ship with object, size between the time threshold values judging its time to closest point of approach and setting, if be less than threshold values, send time danger alarm signal, simultaneously according to the size cases of time to closest point of approach, provide the active collision prevention suggestion that boats and ships slow down.
By such scheme, described hydrographic information and weather information by being arranged in the hydrology, the meteorological sensor collection on this ship top layer deck, or receive hydrographic information, the weather information of official's issue by the mode of broadcast reception.
By such scheme, described confidence parameter beta is determined by following formula:
In formula, SL
1distance between the actual ship position information that the position prediction value of the boats and ships obtained for step 3.1 and this ship receive, SL
2distance between the actual ship position information that the position prediction value of the boats and ships obtained for step 3.2 and this ship receive,
Longitude predicted value px and the latitude predicted value py of the future position that described step 3.3 obtains are obtained by following formulae discovery:
px=β×p
1x+(1-β)×p
2x
py=β×p
1y+(1-β)×p
2y
Wherein: p
1x is the longitude predicted value of the boats and ships that 3.1 obtain; p
2x is the longitude predicted value of the boats and ships that 3.2 obtain, p
1y is the Position Latitude predicted value of the boats and ships that 3.1 obtain; p
2y is the latitude predicted value of the boats and ships that 3.2 obtain.
Realize an inland river bridge district Shipborne navigation initiatively collision avoidance system for above-mentioned inland river bridge district Shipborne navigation active collision prevention method, it is characterized in that: it comprises:
Hydrometeorology information acquisition module, for gathering hydrographic information and weather information; Hydrographic information comprises water level, water flow velocity and current direction; Weather information comprises wind speed and direction;
His ship signal receiving module, for the ship information of boats and ships near being received by watercraft AIS equipment, ship information comprises accommodation, the speed of a ship or plane, course information; Described neighbouring boats and ships are all boats and ships that AIS equipment can receive;
This ship signal receiving module, for being received the ship information of this ship by watercraft AIS equipment, GPS device, ship information comprises accommodation, the speed of a ship or plane, course information;
Inland river electronic channel chart system module, comprises navigation channel base attribute information, and upgrades river figure information for automatic on-line; Navigation channel base attribute information comprises fairway depth, it is wide to navigate, radius-of-curvature, pier location and navigation mark position;
Master database, for depositing hydrographic information, weather information, ship information, pier location and navigation mark position;
Trajectory Prediction module, in conjunction with real-time hydrographic information and weather information, according to the ship information of this ship with his ship, predicts the flight path of this ship and his ship, obtains the flight path information of every ship;
Distance to closest point of approach computing module, for the flight path information obtained by Trajectory Prediction module, calculates distance to closest point of approach and the time to closest point of approach of this ship and object; Object is he ship, bridge pier or navigation mark;
Collision judgment module, for by distance to closest point of approach, this ship dimensional information, the object dimensional information of this ship with object, judges the space risk factor of this ship; The time risk factor of this ship is judged by this ship and the time to closest point of approach of object;
Initiatively collision prevention method suggestion module, the risk factor early warning of boats and ships space is obtained for being less than threshold value at distance to closest point of approach, or time to closest point of approach is less than threshold value when obtaining the risk factor early warning of boats and ships time, for kind and corresponding distance to closest point of approach, the time to closest point of approach of object situation, collision, provide the navigation suggesting method of initiatively collision prevention with regard to this ship speed of a ship or plane, course.
Beneficial effect of the present invention is:
1, the present invention utilizes signal receiver to receive extraneous hydrometeorological information, ship information around, gather this ship information simultaneously, and utilize the accurate bridge pier in the up-to-date electronic channel chart of this ship position acquisition of information, navigation mark positional information, by realizing the prediction to ship's navigation situation, solving spot ship helps navigator accurately cannot obtain collision prevention object position, the defect of anticipation cannot be carried out more accurately to distance to closest point of approach and arrival distance to closest point of approach, make full use of the electronic channel chart information of limited available and energy real-time update, ship information, hydrometeorology information reaches the target of initiatively collision prevention when boats and ships navigate by water in inland river bridge district, ensure the navigation safety of boats and ships in inland river bridge district.
2, by adopting 2 kinds of Trajectory Prediction methods of the present invention to obtain ship track predicted position by the mode that confidence parameter superposes, ship track more accurately can be obtained, for the early warning of boats and ships provides reliable Data support with active collision prevention suggestion.
3, by adopting distance to closest point of approach computing method of the present invention, first find out time point roughly and position, then find out comparatively correct time point and position by synchronous process, finally obtain accurate distance to closest point of approach and time; Can computing time be shortened by this mode, promote computing velocity, thus ensure that real-time to greatest extent, for the early warning of boats and ships provides temporal guarantee with active collision prevention suggestion prompting.
Accompanying drawing explanation
Fig. 1 is the structural representation of one embodiment of the invention.
Fig. 2 is ship track prediction algorithm process flow diagram.
Fig. 3 is the synchronous and boats and ships distance to closest point of approach calculation flow chart in accommodation.
Fig. 4 is collision accident early warning process flow diagram.
Fig. 5 is that initiatively process flow diagram is advised in collision prevention.
Embodiment
Below in conjunction with instantiation and accompanying drawing, the present invention will be further described.
Fig. 1 is the structural representation of one embodiment of the invention, and it comprises:
Hydrometeorology information acquisition module, for gathering hydrographic information and weather information; Hydrographic information comprises water level, water flow velocity and current direction; Weather information comprises wind speed and direction; Hydrographic information and weather information by being arranged in the hydrology, the meteorological sensor collection on this ship top layer deck, or receive hydrographic information, the weather information of official's issue by the mode of broadcast reception;
His ship signal receiving module, for the ship information of boats and ships near being received by watercraft AIS equipment, ship information comprises accommodation, the speed of a ship or plane, course information; Described neighbouring boats and ships are all boats and ships that AIS equipment can receive;
This ship signal receiving module, for being received the ship information of this ship by watercraft AIS equipment, GPS device, ship information comprises accommodation, the speed of a ship or plane, course information;
Inland river electronic channel chart system module, comprises navigation channel base attribute information, and upgrades river figure information for automatic on-line; Navigation channel base attribute information comprises fairway depth, it is wide to navigate, radius-of-curvature, pier location and navigation mark position;
Master database, for depositing hydrographic information, weather information, ship information, pier location and navigation mark position;
Trajectory Prediction module, in conjunction with real-time hydrographic information and weather information, according to the ship information of this ship with his ship, predicts the flight path of this ship and his ship, obtains the flight path information of every ship;
Distance to closest point of approach computing module, for the flight path information obtained by Trajectory Prediction module, calculates distance to closest point of approach and the time to closest point of approach of this ship and object; Object is he ship, bridge pier or navigation mark;
Collision judgment module, for by distance to closest point of approach, this ship dimensional information, the object dimensional information of this ship with object, judges the space risk factor of this ship; The time risk factor of this ship is judged by this ship and the time to closest point of approach of object;
Initiatively collision prevention method suggestion module, the risk factor early warning of boats and ships space is obtained for being less than threshold value at distance to closest point of approach, or time to closest point of approach is less than threshold value when obtaining the risk factor early warning of boats and ships time, for kind and corresponding distance to closest point of approach, the time to closest point of approach of object situation, collision, provide the navigation suggesting method of initiatively collision prevention with regard to this ship speed of a ship or plane, course.
AIS equipment is received by antenna and sends very high frequency(VHF) (VHF) information, the efficiency received and send is subject to the impact of the many reasons such as equipment of itself, barrier, navigation channel tendency, weather, when condition is good, the signal of farther place can be received, and condition bad time, even the ship information of 1000 meters of scopes all may go out active.In the equipment code of AIS, also just mention that AIS receives the ship information of Its Adjacent Waters, but concrete range of receiving does not have clear and definite numerical value, the ship information that the neighbouring boats and ships therefore mentioned in present patent application all can receive with AIS equipment is as the criterion.
Inland river bridge district Shipborne navigation is collision prevention method initiatively, and it comprises the following steps:
Step one, data acquisition:
Gather hydrographic information and weather information, hydrographic information comprises water level, water flow velocity and current direction; Weather information comprises wind speed and direction; The ship information of boats and ships near being received by watercraft AIS equipment, received the ship information of this ship by watercraft AIS equipment, GPS device, ship information comprises accommodation, the speed of a ship or plane, course information; Automatic on-line upgrades river figure information.
Step 2, data store: data step one gathered store.
Step 3, Trajectory Prediction, as shown in Figure 2: in conjunction with real-time hydrographic information and weather information, according to the ship information of this ship with his ship, the flight path of this ship and his ship is predicted, obtains the flight path information of every ship, specifically comprise:
3.1, accommodation variation prediction: according to the variation tendency at history accommodation, utilizes the situation of change of third index flatness to accommodation to predict, obtains the position prediction value of boats and ships, i.e. the predicted value of longitude and latitude;
s′
t=αx
t+(1-α)s′
t-1
s′′
t=αs′
t+(1-α)s′′
t-1
s′′′
t=αs′′
t+(1-α)s′′′
t-1
a
t=3s′-3s′′+s′′′
Wherein, α is smoothing constant, α ∈ (0,1);
X
tfor the longitude (or latitude value) of boats and ships during t;
S '
t-1for a smooth value of t-1 moment boats and ships longitude (or latitude value);
S '
tfor a smooth value of t boats and ships longitude (or latitude value);
S ' '
t-1for the secondary smooth value of t-1 moment boats and ships longitude (or latitude value);
S ' '
tfor the secondary smooth value of t boats and ships longitude (or latitude value);
S ' ' '
t-1for three smooth values of t-1 moment boats and ships longitude (or latitude value);
S ' ' '
tfor three smooth values of t boats and ships longitude (or latitude value);
M is boats and ships longitude (or latitude) predicted value ordinal number;
F
t+mbe m boats and ships longitude (or latitude) predicted value.
Start prediction when receiving second vessel position, now, the initial value of three smooth values required for prediction boats and ships longitude (or latitude value) is the longitude (or latitude value) of first vessel position.
3.2, ship motion prediction: utilize the change trend of third index flatness to speed of the ship in metres per second, course to predict, and then in conjunction with the current accommodation of these boats and ships, the speed of a ship or plane, course, flight path is predicted, then utilize hydrographic information and the drift impact that causes of weather information on this ship track to revise, obtain the position prediction value of boats and ships.
After obtaining the predicted value pvj (k) in the predicted value pv (k) to ship speed, course, according to this ship accommodation, now speed, course, utilize ship motion formula can obtain the accommodation predicted value of boats and ships according to present movement tendency: the distance, delta hx (k) that boats and ships transverse direction and longitude advance; Boats and ships longitudinal direction and latitude advance from Δ hy (k).
Simultaneously wind, failing to be convened for lack of a quorum causes drift action to boats and ships.Obtain horizontal charming appearance and behaviour drift value Δ fx (k), longitudinal charming appearance and behaviour drift value Δ fy (k); Horizontal stream causes drift value Δ lx (k); Longitudinal stream causes drift value Δ ly (k);
The superposition that final predicted position is speed, charming appearance and behaviour drift value and stream cause drift value three.Therefore total transversal displacement:
Δx(k)=Δx(k)+Δfx(k)+Δlx(k)
Total length travel:
Δy(k)=Δy(k)+Δfy(k)+Δly(k)
Due to now, total transverse displacement and total total displacement are all the mileages of the actual walking of boats and ships, are not to carry out measuring with latitude, therefore need to be converted into latitude value.Its transformed representation is:
p
2x=x+Δx(k)/(111319.55×cosx),
p
2y=y+Δy(k)/(111319.55×cosy),
P in formula
2x is the longitude predicted value of the boats and ships that 3.2 obtain, p
2y is the latitude predicted value of the boats and ships that 3.2 obtain, and x is the longitude station of current time boats and ships, and y is the Position Latitude of current time boats and ships.
3.3, integrated forecasting: introduce confidence parameter, accommodation variation prediction and ship motion are predicted the position prediction value at the accommodation that two kinds of methods obtain considers, finally obtain flight path information accurately; Flight path information is made up of future position, and the information of future position comprises longitude predicted value, latitude predicted value and time.
Confidence parameter beta is determined by following formula:
In formula, SL
1distance between the actual ship position information that the position prediction value of the boats and ships obtained for step 3.1 and this ship receive, SL
2distance between the actual ship position information that the position prediction value of the boats and ships obtained for step 3.2 and this ship receive,
Longitude predicted value px and the latitude predicted value py of the future position that described step 3.3 obtains are obtained by following formulae discovery:
px=β×p
1x+(1-β)×p
2x
py=β×p
1y+(1-β)×p
2y
Wherein: p
1x is the longitude predicted value of the boats and ships that 3.1 obtain; p
2x is the longitude predicted value of the boats and ships that 3.2 obtain, p
1y is the Position Latitude predicted value of the boats and ships that 3.1 obtain; p
2y is the latitude predicted value of the boats and ships that 3.2 obtain.
Step 4, distance to closest point of approach calculate, and as shown in Figure 3: the flight path information obtained by step 3, calculate distance to closest point of approach and the time to closest point of approach of this ship and object, specifically comprise:
4.1, be sequence by the future position in this ship and object flight path information with time, successively the pseudo-prediction distance between this ship and the future position of object is calculated, when the monotonicity of pseudo-prediction distance to become from successively decreasing increase progressively time, obtain this ship of pseudo-distance to closest point of approach and correspondence and the future position of object.
4.2, due to when calculating, AIS the transmission frequency in inland river be 30 seconds once, therefore this ship is nonsynchronous with the future position data of object, the pseudo-distance to closest point of approach calculated be asynchronous under distance to closest point of approach, therefore need again by its synchronization, and the future position distance to closest point of approach after synchronization just produces near pseudo-distance to closest point of approach.
Therefore the inventive method is as the criterion with the information of this ship future position corresponding to pseudo-distance to closest point of approach, choose several this ship future positions before and after this this ship future position, the future position information of method of interpolation to object is utilized to carry out time synchronizing, calculate the real prediction distance of this ship corresponding to this ship future position and object, when the monotonicity of prediction distance to become from successively decreasing increase progressively time, obtain the distance to closest point of approach of future position and this ship future position of correspondence; Before and after this selected this ship future position, the number of this ship future position is limited to find the distance to closest point of approach of future position.
The distance to closest point of approach now obtained is the distance to closest point of approach of future position, and the time interval of these future positions is 30 seconds, and the time interval is oversize, not accurately, needs time window to be reduced to 1 second scope.
4.3, be as the criterion with the information of this ship future position corresponding to the distance to closest point of approach of future position, using 1 second as the time interval, utilize method of interpolation, obtain the real prediction distance of this ship before and after this this ship future position in the some time and object, when the monotonicity of prediction distance to become from successively decreasing increase progressively time, obtain distance to closest point of approach and the time to closest point of approach of this definite ship and object; The length of this selected this ship future position surrounding time is limited with the distance to closest point of approach of object to obtain this definite ship;
Object is the one in he ship, bridge pier or navigation mark, when object be bridge pier or navigation mark time, the speed that is considered as by object is his ship of 0.
Step 5, collision accident early warning are advised with active collision prevention, as shown in Figures 4 and 5:
Respectively according to the dimension information of this ship with different target thing, preset the distance threshold values between this ship and different target thing, according to the distance to closest point of approach of this ship with object, size between the distance threshold values judging its distance to closest point of approach and setting, if be less than threshold values, send space danger alarm signal, simultaneously according to the size cases of distance to closest point of approach, provide the active collision prevention suggestion of ship turning;
According to the time to closest point of approach of this ship with object, size between the time threshold values judging its time to closest point of approach and setting, if be less than threshold values, send time danger alarm signal, simultaneously according to the size cases of time to closest point of approach, provide the active collision prevention suggestion that boats and ships slow down.