Location determination system

A location determination system, comprising:

• a vehicle device mounted in a vehicle;
• and
• a mobile terminal provided as a communication terminal to be carried by a user of the vehicle and set to transmit a radio signal including transmission source information at least once within a predetermined period of time, wherein
• the vehicle device includes:
• a reception portion configured to receive the radio signal transmitted from the mobile terminal via an antenna disposed in the vehicle and detect a reception strength of the received radio signal;
• and
• a location determination portion configured to determine, based on the reception strength of the radio signal detected by the reception portion, whether the mobile terminal is present inside a target area set in advance based on a position at which the antenna is disposed, wherein,
• as determination thresholds for the location determination portion to determine whether the mobile terminal is present inside the target area based on the reception strength of the radio signal detected by the reception portion, two parameters that are a high level threshold and a low level threshold lower than the high level threshold are set, wherein,
• when the location determination portion has previously determined that the mobile terminal is present outside the target area, the location determination portion is configured to determine that the mobile terminal has moved from outside the target area to inside the target area in response to the reception strength of the radio signal detected by the reception portion becoming greater than or equal to the high level threshold, and wherein,
• when the location determination portion has previously determined that the mobile terminal is present inside the target area, the location determination portion is configured to determine that the mobile terminal has moved from inside the target area to outside the target area in response to the reception strength of the radio signal detected by the reception portion becoming less than or equal to the low level threshold.