Navigation system for transmitting real-time information allowing instant judgement of next action

A navigation system comprising:

• a database holding real-time information indicating a ground state;
• a server receiving positional information including a present position of a client through a communication network, determining, as an information extraction range, a certain region on a map wider than a surrounding area of said present position based on said positional information, extracting, as information to be transmitted, real-time information failing within said information extraction range from said database, adding a header identifiable by said client to the extracted real-time information, and transmitting the header-added real-time information through said communication network at random;
• and
• a navigator transmitting said positional information to said server through said communication network, receiving information from said server through said communication network, detecting said extracted real-time information from the received information while using said header, and displaying the detected real-time information, wherein
• said server receives surrounding information on the client from a plurality of clients, and updates the real-time information in said database using the received surrounding information.