A conventional position detection method typically involves measuring a position of an object using signals transmitted from a satellite, such as a GPS.
Another known position detection method involves receiving signals transmitted from a plurality of access points at a terminal, and calculating the position of the terminal from differences in times of reception of the signals.
More specifically, a method for detecting the position of a mobile terminal in a cellular phone system has been proposed which includes calculating the differences in the reception times of signals transmitted from the access points to the mobile terminal (e.g. differences in propagation times of the signals from the respective access points to the mobile terminal T1−T2 and T3−T2), and multiplying the propagation time differences by light velocity to calculate differences in propagation distances of the signals from the mobile terminal to the respective access points, thereby determining the position of the terminal, in the following manner (see patent document 1).D1−D2=c(T1−T2)D3−D2=c(T3−T2)
Another method for detecting a position of a node in a wireless LAN system has been proposed which includes calculating differences in reception times of a signal (differences between the reception times at the respective access points Ti−Tl), which has been transmitted from the node (terminal) and received at the access points, and multiplying the reception time differences by light velocity to calculate differences between propagation distances of the signal from the node to the respective access points ({[P−Pi]−[P−Pl]}=c (Ti−Tl), i=2, . . . , n), thereby detecting or determining the position of the node, in the following manner (see patent document 2).    [Patent document 1] JP-A No. 181242/1995    [Patent document 2] JP-A No. 101254/2004