Information of position on the earth is sought making use of the map

摘要

PROBLEM TO BE SOLVED: To omit a repetition procedure for displaying the position of a portable radio terminal in its map picture clearly in detail. SOLUTION: The portable radio terminal 10 and a positioning server group 20 find the position of the portable radio terminal 10 on the earth by using GPS and when a reduced map based upon the position information is received from a map server included in the positioning server group 20 and displayed as a picture on the display part of the portable ratio terminal 10, a reduction scale selecting means 50 automatically selects a scale of the map according to the precision of the position information found by GPS. Namely, when the precision of the position information is high, a narrow range is expanded and displayed and when the precision is low, on the other hand, a scale covering the range is automatically selected. The scale selecting means can be actualized as a stand-alone type by being incorporated in the portable radio terminal 10. The precision is judged from satellite positions, the number of satellites, and the signal-to-noise ratios of GPS signals.