1. Technical Field
The present invention relates to a positioning device, a mobile terminal, a positioning method, and a positioning program and particularly to those suitably used for a GPS (Global Positioning System).
2. Related Art
At present, as a ground position determination system, a GPS which is called NAVSTAR and operated by the U.S. government is known as disclosed in Parkinson, Bradford W Gilbert, Stephen W.; “NAVSTAR: Global Positioning System—Ten Years Later”; Proceedings of the IEEE; Vol. 71; No. 10. This GPS is a wireless navigation system which is designed for providing highly accurate three-dimensional information to a recipient on or near the ground, the GPS using a satellite as a transmitter.
Also, the former Union of Soviet Socialist Republics government operates a GPS known as GLONASS. Further, a system known as GALILEO is under development by the European Community. Recently, a GPS receiving device is used as a car navigation system.
Also, in JP-A-6-118156, for example, a method of downsizing the GPS receiving device to obtain a direction and a distance of a person's movement while the person is walking so that the person can carry the device is disclosed.
Further, JP-A-2001-133535, for example, discloses a method of reducing positioning time by using location information of a base station acquired by a PHS communication as an initial location for the positioning using the GPS.
JP-A-2001-235337, for example, discloses a method of reducing positioning time by using a field intensity map of a base station in a mobile communication network as an initial location for the positioning using the GPS.
However, in the method of reducing GPS positioning time by using the location information of the base station on the mobile communication network as the initial location, it is necessary to receive the location information by communicating with the base station or to store the location information of the base station in a GPS receiver. The method of communicating with the base station for the purpose of acquiring the location information of the base station has the problem of communication cost, thereby undesirably increasing a burden on a user. Also, the method of storing the location information of the base station in the GPS receiver has the problem that, in the case where multiple base stations exist at an interval of a several kilometers, a large memory capacity is required for storing the base stations.
Further, with the method of using the location information of the base station on the mobile communication network as the initial location, even in the case where the previous positioning information can be used as the initial location for the current positioning, it is necessary to confirm the location information of the base terminal by communicating again with the base terminal and to use the newly obtained location information of the base terminal as the initial location for the current positioning, thereby raising a problem of wasteful communication.
Accordingly, an object of the present invention is to provide a positioning device, a mobile terminal, a positioning method, and a positioning program capable of reducing the time required for positioning by a GPS without allowing specific parties to occupy a communication channel.