Navigation display apparatus for collison avoidance utilizing polygonal safety regions and predicted danger areas

A navigation supporting display apparatus comprising;

• collision point calculation means for calculating a possible collision point of each vertex of a polygonal safe passing region set around one's own navigating ship, and a target ship, from the relative position of the target ship, the velocity vector of the target ship and the velocity of the navigating ship;
• own-ship-mapping-position calculation means for calculating a position at which the navigating ship would be located when each of the vertexes of the safe passing region is on the possible collision point obtained by the collision point calculation means, and for defining the calculated position as an own-ship-mapping position;
• and
• danger area calculation means for calculating and determining lines joining the own-ship-mapping-positions corresponding to the possible collision point of the vertexes of the safe passing region, said lines defining a danger area, and output information on the lines and own-ship-mapping-positions to display means,
• said danger area calculation means determining the lines joining the own-ship-mapping-positions depending on the number of the possible collision points of each vertex of the safe passing region as follows,
• i) when the vertexes have one or no collision points, respectively, the danger area calculation means determining lines such that the own-ship-mapping-positions corresponding to the collision points corresponding to the vertexes neighboring each other are connected with each other by one of the lines, so that the lines define a closed area, or one or more open areas;
• ii) when the vertexes have two collision points, the danger area calculation means judging which one of the two collision points need a longer time to move from the present vertex's position to the collision point, and which one of the two collision points need a shorter time to move from the present vertexes position to the collision point, classifying one of the two collision points needing longer time into a longer time group and the other of the two collision points needing shorter time into a shorter time group, and determining lines such that the own-ship-mapping-positions corresponding to the collision points belonging to the longer group and corresponding to the vertexes neighboring each other are connected with each other by one of the lines, and determining lines such that the own-ship-mapping-positions corresponding to the collision points belonging to the shorter time group and corresponding to the vertexes neighboring each other are connected with each other by one of the lines so that the lines define two separate danger areas:
• iii) when one or more vertexes have one collision point and the other vertexes have two collision points, respectively, the danger area calculation means judging, for the other vertexes having two collision points, which one of the two collision points needs a longer time to move from the present vertex's position to the collision point, and which one of the two collision points needs a shorter time to move from the present vertex's position to the collision point, classifying one of the two collision points needing a longer time into a longer time group and the other of the two collision points needing a shorter time into a shorter time group, assuming that, for vertexes having one collision point, the collision point belongs to either group and determining lines such that the own-ship-mapping-positions corresponding to the collision points belonging to the longer group and corresponding to the vertexes neighboring each other are connected with each other by one of the lines, and determining lines such that the own-ship-mapping positions corresponding to the collision points belonging to the shorter time group and corresponding to the vertexes neighboring each other are connected with each other by one of the lines, so that the lines define and form two danger areas in contact with each other;
• and
• iv) when there are vertexes having no collision points and vertexes having two collision points, the danger area calculation means judging, for the vertexes having two collision points, which one of the two collision points needs a longer time to move from the present vertex's position to the collision point, and which one of the two collision points needs a shorter time to move from the present vertex's position to the collision point, classifying one of the two collision points needing a longer time into a longer time group and the other of the two collision points needing a shorter time into a shorter time group, assuming that, if there are vertexes having one collision point, the collision point belongs to either group, and determining lines such that the own-ship-mapping-positions corresponding to the collision points belonging to the longer time group and corresponding to the vertexes neighboring each other are connected with each other by one of the lines, and determining lines such that the own-ship-mapping-positions corresponding to the collision points belonging to the shorter time group and corresponding to the vertexes neighboring each other are connected with each other by one of the lines, if a neighboring vertex has no collision points, two own-ship-mapping-positions corresponding to the two collision points corresponding to a vertex which neighbors with the vertex having no collision are connected with each other by one of the lines, so that the lines define two danger areas overlapping each other,
• whereby said apparatus supports ship navigation by providing the danger area where there is the danger of collision between the navigating ship and the target ship.