A data transmission terminal, agent program, location estimation system and location estimating method

That includes employed in a location estimation system data transmission terminal apparatus, a plurality of communication terminals and a management server, which is connected to a wired network and is arranged so that it estimates a location of each of the plurality of communication terminals, and then registered location data of the data transmission terminal and managed, said data transmission terminal apparatus is used by executing a program installed agents as agent means, said agent means: a connection judging unit that performs the following: Verifying a network connection state of the data transfer terminal, and Judging whether said data transmission terminal apparatus is connected to the wired network; a terminal data transmitting unit which, when the communication terminal is found as connected to the wired LAN executes the following: Sending terminal identification data which include a network address of the data-communication terminal which has been assigned by an address assignment unit, to the management server, and Causing the management server to generate location data of the data transmission terminal based on the network address and to register the location information in association with the terminal identifier and manage data; To change a data transmission mode change unit, led by receiving a mode change command from the management server to change in a data transmission mode for performing a wireless communication directly with another of the data transmission terminals, the data transmission terminal apparatus in the data transfer mode and a pseudo access point (PAP) to serve; a carrier wave transmission unit that transmits a carrier wave, which have been added to the terminal identification information of said data transmission terminal as PAP; an intensity measuring unit that, when the data transmission terminal apparatus is determined to be not connected to the wired network, measures an intensity of a carrier wave which is transmitted through a different one of the data transfer terminal, which serves as PAP, and the terminal ID data of the other data transmission -Endgerats have been added; and a measurement result transmission unit which performs the following: Sending the measured intensity along with the terminal identity data of the other data transfer terminal, which serves as PAP, to the management server, and Causing the management server, location data of said data transmission terminal using the location data of the other data transfer terminal, which serves as PAP, and the measured intensity to estimate and to register the estimated location data in association with the terminal identifier information of said data transmission terminal and manage; wherein after receiving the mode change command from the management server to change in a data transmission mode for performing wireless communication through an access point connected to the wired network, the data transfer mode change unit causes the communication terminal to switch to data transmission mode and, as non-PAP to serve.