A position information management system in which a portable remote terminal includes a plurality of kinds of positioning means for positioning based on a GPS, positioning based on a portable-telephone or PHS base station, positioning based on a radio marker, and independent positioning based on a direction detector, so that the holder of the portable remote terminal can be navigated anywhere. The holder of the portable remote terminal can know the position of a third party similarly holding such a portable remote terminal, by inquiring of a central system, and he/she can supervise, for example, the action of an old person, a child, or a skier in a skiing area. Further, only the map data of a district which is often used by the holder is stored in the portable remote terminal. In this regard, when the holder is in a district not contained within the retained map data, he/she downloads corresponding map data from the central system and uses the downloaded map data.

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> Method and device for noise detection

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