Small boat collision avoidance apparatus

An apparatus installed on a boat (A) in a plurality of boats including at least (A, B) for avoiding collision with the boat (B), comprising:

• a first radio-wave transceiver unit (110A) installed at a first position and capable of transmitting to and receiving radio waves of a predetermined frequency from the boat (B);
• a second radio-wave transceiver unit (110B) of a type same as the first radio-wave transceiver unit (110A) and installed at a second position spaced apart from the first position of the first radio-wave transceiver (110a), the second radio-wave transceiver unit (110B) being capable of transmitting to and receiving radio wave of the predetermined frequency from the boat (B);
• a first distance calculating unit (84Aa) that calculates a first clearance distance from the boat (B) based on an attenuation degree of the radio wave transmitted from the boat (B) and received by the first radio-wave transceiver (110A);
• a second distance calculating unit (84Ba) that calculates a second clearance distance from the boat (B) based on the attenuation degree of the radio wave transmitted from the boat (B) and received by the second radio-wave transceiver (110B);
• an intersection point calculating unit (84Ab) that calculates an intersection point (p) of circles comprised of at least a first circle (c1) whose origin in an x-y coordinate plane is set to a position corresponding to the first position of the first radio-wave transceiver unit (110A) and whose radius is set to a value corresponding to the first clearance distance calculated by the first distance calculating units (84Aa) and a second circle (c2) whose origin in the x-y coordinate plane is set to a position corresponding to the second position of the second radio-wave transceiver unit (110B) and whose radius is set to a value corresponding to the second clearance distance calculated by the second distance calculating units (84Ba);
• a position estimating unit (84Ac) that estimates direction and position of the boat (B) based on the intersection point of the circles in the x-y coordinate plane calculated by the intersection point calculating unit (84Ab);
• and
• a collision avoidance instructing unit (84Ad) that issues an instruction to an operator of the boat (A) necessary for avoiding collision with the boat (B) based on the direction and position estimated by the position estimating unit (84Ac).