PURPOSE: To prevent and reduce the collision accident of a sailing ship and to lighten the burden on a maneuvering person by indicating data on the position and state of a specific ship with a synthesized voice of natural language and displaying an image of a dangerous sea area in a sailing route.

CONSTITUTION: Data on the position, azimuth, and speed of a ship to be caught and the speed, course, etc., of this ship are received together from a radar to detect a dangerous ship, a ship which has possible dangerousness, a request ship, or miscaught ship according to the ship sailing state and motion characteristics of this ship and other ships. Then, the positions and meeting state of those ships are analyzed and knowledge processing is performed on the basis of data on the kind of an alarm, the relative position of targets, the meeting state, etc., to generate a vocabulary list of voice indications on a computer. Assistance information in synthesized voice is generated from the vocabulary list and the indexes of a voice word dictionary to display image information on a closed sea area viewed from this ship side and other ship sides, the value of the degree of blocking in the course of this ship on a closest time axis, its maximum value and the minimum value of the closest distance, etc., on a CRT display.