Recently, navigation systems combining GPS (Global Positioning System) and the autonomous navigation become widely used. In recent days, portable mobile terminals such as mobile phones, to which the navigation system is mounted, appear.
Japanese Patent Application Publication No. 2009-115514 (Document 1) discloses an art of which the object is to solve the problem in a capability of following an output position of GPS when turning to the right or the left with keeping continuity or straightness of a trajectory of the output position of GPS while traveling in a straight line. In this art, GPS positioning is carried out intermittently and a turn in the traveling direction is detected with a gyro sensor. In addition, the output position of GPS is determined with a polytomous regression estimation process while traveling in a straight line, and the output position of GPS is determined with a binary smoothing process when turning to the right or the left.
Japanese Patent Application Publication No. 2009-92506 (Document 2) discloses an art of which the object is to determine a positioning timing at a necessary position automatically depending on the situation with saving a power in the mobile terminal device carried by a walking user. In this art, as GPS positioning is carried out at the start of the navigation, the number of steps till the next positioning timing is calculated based on a distance or a route from the current measured position to the destination. Then, when a pedometer counts the calculated number of steps, next GPS positioning is carried out, and the number of steps till the next positioning timing is calculated on the basis of the calculated current position. In this case, the number of steps till the next positioning timing is set to smaller value as the number of steps to the position where the user changes the path in the route from the measured current position to the destination or the distance from the measured current position to the destination becomes shorter.
In this kind of navigation system, the reduction of power consumption of sensors, which carry out various measurements, is studied to achieve an autonomous positioning for many hours.