Reduced-power GPS-based system for tracking multiple objects from a central location

Claim 1

A method for identifying location of an object to be tracked, comprising: measuring data related to propagation time differences between signals transmitted from a plurality of GPS satellites and received at said object to be tracked, said data comprising code word phase measurements μ i for a satellite at a time t R , where μ 1 =γ i /T i C , and defined as time elapsed to time t R from the beginning of a code word in the signal from satellite i in which t R falls, T i C being defined as the code period for satellite i at time t R in the signal received from satellite i, said code word phase measurements being simultaneously derived from the signals transmitted from said plurality of satellites and received at the object to be tracked; transmitting said data to a central station; and calculating at said central station the location of said object to be tracked based upon the transmitted data and data derived from at least one receiver apart from said object to be tracked receiving said signals from said plurality of satellites.

Claim 2

A method for identifying location of an object to be tracked, comprising: measuring data related to propagation time differences between signals transmitted from a plurality of GPS satellites and received at said object to be tracked, said data comprising code word phase measurements μ i for a satellite at a time t R , where μ 1 =γ i /T i C , and defined as time elapsed to time t R from the beginning of a code word in the signal from satellite i in which t R falls, T i C being defined as the code period for satellite i at time t R in the signal received from satellite i, said code word phase measurements being simultaneously derived from the signals transmitted from said plurality of satellites and received at the object to be tracked; transmitting said data to a central station; and calculating at said central station the location of said object to be tracked based upon the transmitted data and data derived from at least one receiver apart from said object to be tracked receiving said signals from said plurality of satellites.

Claim 6

A method for identifying location of an object to be tracked comprising: measuring data related to propagation time differences between signals transmitted from a plurality of GPS satellites and received at said object to be tracked, said data comprising bit phase measurements μ i for a satellite i at a time t R , where μ i =β i /T i B , β i being the receiver bit-time offset for satellite i and defined as time elapsed to time t R from the beginning of a code word in the signal from satellite i in which t R falls, T i B being defined as the bit period for satellite i at time t R in the signal received from satellite i, said bit phase measurements being simultaneously derived from the signals transmitted from said plurality of satellites and received at the object to be tracked; transmitting said data to a central station; and calculating at said central station the location of said object to be tracked based upon the transmitted data and data derived from at least one receiver apart from said object to be tracked receiving said signals from said plurality of satellites.

Claim 7

A method for identifying location of an object to be tracked comprising: measuring data related to propagation time differences between signals transmitted from a plurality of GPS satellites and received at said object to be tracked, said data comprising bit phase measurements μ i for a satellite i at a time t R , where μ i =β i /T i B , β i being the receiver bit-time offset for satellite i and defined as time elapsed to time t R from the beginning of a code word in the signal from satellite i in which t R falls, T i B being defined as the bit period for satellite i at time t R in the signal received from satellite i, said bit phase measurements being simultaneously derived from the signals transmitted from said plurality of satellites and received at the object to be tracked; transmitting said data to a central station; and calculating at said central station the location of said object to be tracked based upon the transmitted data and data derived from at least one receiver apart from said object to be tracked receiving said signals from said plurality of satellites.

Claim 13

A method for identifying location of an object to be tracked comprising: measuring data related to propagation time differences between signals transmitted from a plurality of satellites and received at said object to be tracked, said data comprising receiver code-time offsets for a satellite i and defined as time elapsed to a time t R from the beginning of a code word in the signal from satellite i in which t R falls, and code periods in the signal received from satellite i in which time t R falls, said plurality of satellites comprising GPS satellites, and including the additional step of simultaneously deriving said receiver code-time offsets and code periods from signals received from the plurality of satellites at said object to be tracked; transmitting said data to a central station; and calculating at said central station the location of said object to be tracked based upon the transmitted data and data derived from at least one receiver apart from said object to be tracked receiving said signals from said plurality of satellites.

Claim 14

A method for identifying location of an object to be tracked comprising: measuring data related to propagation time differences between signals transmitted from a plurality of satellites and received at said object to be tracked, said data comprising receiver code-time offsets for a satellite i and defined as time elapsed to a time t R from the beginning of a code word in the signal from satellite i in which t R falls, and code periods in the signal received from satellite i in which time t R falls, said plurality of satellites comprising GPS satellites, and including the additional step of simultaneously deriving said receiver code-time offsets and code periods from signals received from the plurality of satellites at said object to be tracked; transmitting said data to a central station; and calculating at said central station the location of said object to be tracked based upon the transmitted data and data derived from at least one receiver apart from said object to be tracked receiving said signals from said plurality of satellites.

Claim 15

A method for identifying location of an object to be tracked, comprising: measuring data related to propagation time differences between signals transmitted from at least four GPS satellites and received at said object to be tracked, said data related to propagation time differences comprising bit phase measurements simultaneously derived from said signals; transmitting said data, including satellite identification data, to a central station; measuring, at said object to be tracked, delay between the time at which the data are recorded and the time when the data are transmitted to the central station; transmitting the measured delay to said central station; and calculating at said central station the location of said object to be tracked based upon the transmitted data, the satellite identification data, and data derived from at least one receiver apart from said object to be tracked receiving said signals from said plurality of satellites, the calculating step comprising: assuming a feasible value for a communication time delay required for a signal transmitted from said object to be tracked to reach the central station; calculating the location of said object to be tracked based upon the satellite identification data and the assumed value of said communication time delay; calculating a new value for said communication time delay based upon the calculated location of said object to be tracked; and calculating a corrected location of said object to be tracked based upon the calculated new value for said communication time delay.

Claim 16

A method for identifying location of an object to be tracked, comprising: measuring data related to propagation time differences between signals transmitted from at least four GPS satellites and received at said object to be tracked, said data related to propagation time differences comprising bit phase measurements simultaneously derived from said signals; transmitting said data, including satellite identification data, to a central station; measuring, at said object to be tracked, delay between the time at which the data are recorded and the time when the data are transmitted to the central station; transmitting the measured delay to said central station; and calculating at said central station the location of said object to be tracked based upon the transmitted data, the satellite identification data, and data derived from at least one receiver apart from said object to be tracked receiving said signals from said plurality of satellites, the calculating step comprising: assuming a feasible value for a communication time delay required for a signal transmitted from said object to be tracked to reach the central station; calculating the location of said object to be tracked based upon the satellite identification data and the assumed value of said communication time delay; calculating a new value for said communication time delay based upon the calculated location of said object to be tracked; and calculating a corrected location of said object to be tracked based upon the calculated new value for said communication time delay.

Claim 18

A system for identifying location of an object to be tracked, comprising: means for measuring data related to propagation time differences between signals transmitted from a plurality of GPS satellites and received at said object to be tracked, each of said signals identifying an associated satellite, said object to be tracked including: receiver means for receiving signals from at least four GPS satellites; and first processor means for processing data from the receiver means at predetermined time intervals in synchronism with received signal events, said data being related to propagation time differences for said signals; receiver means apart from said object for receiving said signals transmitted from said plurality of satellites; a central station for calculating the location of said object based upon the measured data, data derived from said receiver means apart from said object, and the satellite identification data; and transmission means for transmitting the processed data to said central station; said system further including: second processor means at said central station for determining the location of said object based on the data received from said transmission means and data derived from said receiver means apart from said object.

Claim 19

A system for identifying location of an object to be tracked, comprising: means for measuring data related to propagation time differences between signals transmitted from a plurality of GPS satellites and received at said object to be tracked, each of said signals identifying an associated satellite, said object to be tracked including: receiver means for receiving signals from at least four GPS satellites; and first processor means for processing data from the receiver means at predetermined time intervals in synchronism with received signal events, said data being related to propagation time differences for said signals; receiver means apart from said object for receiving said signals transmitted from said plurality of satellites; a central station for calculating the location of said object based upon the measured data, data derived from said receiver means apart from said object, and the satellite identification data; and transmission means for transmitting the processed data to said central station; said system further including: second processor means at said central station for determining the location of said object based on the data received from said transmission means and data derived from said receiver means apart from said object.

Claim 22

A method for identifying location of an object to be tracked comprising: means for measuring data related to propagation time differences between signals transmitted from a plurality of GPS satellites and received at said object to be tracked, each of said signals identifying an associated satellite, said object to be tracked including: receiver means for receiving signals from at least four GPS satellites; and first processor means for calculating a receiver bit phase for each of said satellites, said bit phase for any satellite i at a time t R being defined as β i /T i B , β i being the receiver bit-time offset for satellite i and defined as time elapsed to time t R from the beginning of a code word in the signal from satellite i in which t R falls, and T i B being defined as the bit period for satellite i at time t g in the signal received from satellite i; receiver means apart from said object for receiving said signals from said plurality of satellites; a central station; and transmission means for transmitting the calculated bit phases to said central station; said system further including: second processor means at said central station for determining signal propagation times between said plurality of satellites and said object and for determining location of said object based upon the bit phases transmitted by said transmission means and data derived from said receiver means apart from said object.

Claim 23

A method for identifying location of an object to be tracked comprising: means for measuring data related to propagation time differences between signals transmitted from a plurality of GPS satellites and received at said object to be tracked, each of said signals identifying an associated satellite, said object to be tracked including: receiver means for receiving signals from at least four GPS satellites; and first processor means for calculating a receiver bit phase for each of said satellites, said bit phase for any satellite i at a time t R being defined as β i /T i B , β i being the receiver bit-time offset for satellite i and defined as time elapsed to time t R from the beginning of a code word in the signal from satellite i in which t R falls, and T i B being defined as the bit period for satellite i at time t g in the signal received from satellite i; receiver means apart from said object for receiving said signals from said plurality of satellites; a central station; and transmission means for transmitting the calculated bit phases to said central station; said system further including: second processor means at said central station for determining signal propagation times between said plurality of satellites and said object and for determining location of said object based upon the bit phases transmitted by said transmission means and data derived from said receiver means apart from said object.

Claim 24

A system for identifying location of an object to be tracked, comprising: means for measuring data related to propagation time differences between signals transmitted from a plurality of GPS satellites and received at said object to be tracked, each of said signals identifying an associated satellite, said object to be tracked including: receiver means for receiving signals from at least four GPS satellites, and first processor means for calculating a bit-time offset for each of said satellites and for determining a bit period for each signal received from said satellites, said bit-time offset for a satellite i being defined as time elapsed to a time t R from the beginning of a code word in the signal from satellite i in which t R falls, said bit period for satellite i being determined at time t R in the signal from satellite i; receiver means apart from said object for receiving said signals from said plurality of satellites; a central station; and transmission means for transmitting time stamps, the calculated bit-time offsets and bit periods, and satellite identification data, to said central station; said system further including: second processor means at said central station for determining signal propagation times between said plurality of satellites and said object and for determining location of said object based upon the bit-time offsets and periods, time stamps, satellite identification data transmitted by said transmission means, and data derived from said receiver means apart from said object.

Claim 25

A system for identifying location of an object to be tracked, comprising: means for measuring data related to propagation time differences between signals transmitted from a plurality of GPS satellites and received at said object to be tracked, each of said signals identifying an associated satellite, said object to be tracked including: receiver means for receiving signals from at least four GPS satellites, and first processor means for calculating a bit-time offset for each of said satellites and for determining a bit period for each signal received from said satellites, said bit-time offset for a satellite i being defined as time elapsed to a time t R from the beginning of a code word in the signal from satellite i in which t R falls, said bit period for satellite i being determined at time t R in the signal from satellite i; receiver means apart from said object for receiving said signals from said plurality of satellites; a central station; and transmission means for transmitting time stamps, the calculated bit-time offsets and bit periods, and satellite identification data, to said central station; said system further including: second processor means at said central station for determining signal propagation times between said plurality of satellites and said object and for determining location of said object based upon the bit-time offsets and periods, time stamps, satellite identification data transmitted by said transmission means, and data derived from said receiver means apart from said object.