Portable position detector and position management system

A portable position detector and a position management system that are capable of accurately detecting the direction of a walking body even when GPS signals cannot be received (or without reception) and thereby enhancing the accuracy of the dead reckoned position of the walking body. The portable position detector is equipped with a pedometer and a geomagnetic sensor. With the pedometer, the moved distance of a walker is detected by a calculation of "the number of stepsxthe length of a step". The moved direction is detected with the geomagnetic sensor. With this, the moved position of the walker is accurately detected by the self-contained navigation system. Particularly, even in the case where the position detector is located in a forest or between buildings where a signal cannot be received from a global positioning system (GPS) due to high buildings, banks, and forests, the position detector with a portable size and weight applicable to a walker can know with a practically sufficient degree of accuracy the position of a person carrying this portable detector by the self-contained navigation system.