An object locator device is disclosed for use in conjunction with both a GPS
satellite system and a two-way communication
satellite. The object locating
system includes a mobile unit physically connected to the object to be located. The mobile unit includes a
satellite communication
transceiver capable of receiving and transmitting encoded signals. A decoder is associated with the satellite communication
transceiver for decoding a unique
signal associated with that mobile unit and for generating an activation
signal upon
receipt of the unique
signal. The mobile unit further includes a
GPS receiver which is activated in response to the
receipt of the unique signal so that the
GPS receiver generates a position signal representative of the position of the mobile unit. The output signal from the
GPS receiver is connected as an input signal to the satellite communication
transceiver such that the satellite communication transceiver transmits the.position signal to a
base station on the communication satellite. The
base station physically separated from the
remote unit is operable to both transmit the unique signal to the communication satellite in order to activate the mobile unit as well as for receiving the position signal from the communication satellite following activation. The
base station creates a display representative of the location of the mobile unit. Preferably, this display signal is transmitted via a
telephone line and modem to a computer which generates the display on a
computer monitor.
Energy conservation algorithms including periodic activation of the satellite communication transceiver as well as activation of the satellite communication transceiver only when the position of the mobile unit has changed more than a threshold amount between periodic signals is disclosed.