To transmit position information for a traveling object to a personal computer by using an internet line and to display it with stored map information on a screen of the personal computer.

GPSs 112 and 212 which are provided to automobiles 110 and 210 respectively measure a position of each automobile 110 and 210. Positional information is transmitted from the GPSs 112 and 212 to a network server 22, via respective radio transmitters 114 and 214 and a radio receiver 20. The server 22 converts the positional information into a packet unit, only when the difference between a measured position P which is included in the positional information and a predicted position X which is calculated, based on positional information that is measured last time excess an enabling error range E. The positional information is transmitted to each of personal computers 126 and 226 via an internet line 24, and the positions of the automobiles 110 and 210 are shown on respective screens 128 and 228 together with stored map information.