Position-verified access apparatus, method, and program product

1. An apparatus comprising:

a receiver which receives a device distance and a device position from a position detecting device which measures the device distance from the position detecting device to each of a plurality of satellites and calculates the device position that is the position of the position detecting device based on the device distance and the position of each of the plurality of satellites;

a verification position calculator, coupled to said receiver, which calculates a verification position that is the position to be calculated by the position detecting device, based on the received device distance and the position of each of the plurality of satellites at the time of measuring the device distance;

a validity circuit, coupled to said verification position calculator, which judges that the device position detected by the position detecting device is valid, on condition that the device position is coincident with the verification position; and

a distance calculator, coupled to said validity circuit, which calculates the distance between the position of each of the plurality of satellites at the time of measuring the device distance by the position detecting device and the device position received by said receiver; wherein the validity circuit judges that the device position is valid, further provided that the device distance received by said receiver differs from the distance calculated by said distance calculator by a predetermined difference value or more.

2. The apparatus according to claim 1 , wherein the apparatus wirelessly communicates with the position detecting device over at least one wireless communication base station; wherein said verification position calculator calculates as another verification position the position to be calculated by the position detecting device, based on the position of the wireless communication base station over which communication with the position detecting device wirelessly occurs; and wherein said validity circuit judges that the device position detected by the position detecting device is valid, further provided that the distance between the other verification position and the device position is within a predetermined reference distance.

3. The apparatus according to claim 1 , wherein said validity circuit judges that the device position is valid, further provided that a time which has elapsed since the position detecting device measures the device distance until said receiver receives the device distance and the device position is less than a predetermined reference time.

4. The apparatus according to claim 1 , wherein the position detecting device measures the device distances between the position detecting device and each of at least five satellites, based on a time elapsed since each of the at least five satellites transmit a signal and until the position detecting device receives the signal; and wherein said verification position calculator calculates the verification position based on an equation, for each of the at least five satellites, whose unknowns are a clock error of the position detecting device and each element of the vector showing the coordinates of the device position, the equation showing that the distance to the satellite measured by the position detecting device, plus the clock error multiplied by the signal velocity is equal to the distance calculated based on the position of each of the at least five satellites and the device position.

5. The apparatus according to claim 1 , wherein said receiver further receives from the position detecting device a device type identification information identifying the device type of the position detecting device; and wherein said verification position calculator calculates the verification position by a predetermined calculating method corresponding to the device type identification information.

6. A method comprising:

receiving a device distance and a device position from a position detecting device which measures the device distance from the position detecting device to each of a plurality of satellites and calculates the device position that is the position of the position detecting device based on the device distance and the position of each of the plurality of satellites;

calculating a verification position that is the position to be calculated by the position detecting device, based on the received device distance and the position of each of the plurality of satellites at the time of measuring the device distance;

calculating a distance that is the distance between the position of each of the plurality of satellites at the time of measuring the device distance by the position detecting device and the received device position; and

judging that the device position detected by the position detecting device is valid, on condition that the device position is coincident with the verification position and that the received distance differs from the calculated distance by a predetermined difference value or more.

7. The method of claim 6 , wherein the plurality of satellites are Global Positioning System satellites.

8. The method of claim 6 , further comprising:

receiving device type information that identifies a type of the position detecting device; and

selecting a predetermined method for calculating the verification position based at least in part upon the type of the position detecting device.

9. A product comprising:

a computer usable medium having computer readable program code stored therein, the computer readable program code in said product being effective to:

receive a device distance and a device position from a position detecting device which measures the device distance from the position detecting device to each of a plurality of satellites and calculates the device position that is the position of the position detecting device based on the device distance and the position of each of the plurality of satellites;

measure the device distances between the position detecting device and each of the plurality of satellites, based on a time elapsed since each of the plurality of satellites transmits a signal and until the position detecting device receives the signal;

calculate a verification position that is the position to be calculated by the position detecting device, based on the received device distance and the position of each of the plurality of satellites at the time of measuring the device distance, wherein the verification position is calculated based on an equation, for each of the plurality of satellites, whose unknowns are a clock error of the position detecting device and each element of the vector showing the coordinates of the device position, the equation showing that the distance to the satellite measured by the position detecting device, plus the clock error multiplied by the signal velocity, is equal to the distance calculated based on the position of each of the plurality of satellites and the device position; and

judge that the device position detected by the position detecting device is valid, on condition that the device position is coincident with the verification position and that the received distance differs from the calculated distance by a predetermined difference value or more.

10. The product of claim 9 , wherein the computer readable program code in said product being further effective to:

receive device type information that identifies a type of the position detecting device; and

select a predetermined method for calculating the verification position based at least in part upon the type of the position detecting device.