Patent ID: 8188922

Claim:
A position information acquisition device comprising: a first communication unit to communicate with at least another position information acquisition device; a detection unit to detect whether a number of other position information acquisition devices that are not communicable with the first communication unit reaches a threshold or higher based on history information that records position information of the other position information acquisition devices that were previously communicable with the first communication unit and information of the other position information acquisition devices that are currently communicable with the first communication unit; the position information acquisition device determining that the position information acquisition device is moved when the threshold is reached and determining that the position information acquisition device is not moved when the threshold is not reached; a position measuring unit to measure a position of the position information acquisition device when the detection unit performs a detection; and a second communication unit to transmit position information measured by the position information measuring unit to a server that manages position information of the position information acquisition device and the other position information acquisition devices.