Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
1999-07-12
2001-06-05
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S207000, C701S215000, C342S357490, C379S056200
Reexamination Certificate
active
06243648
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to methods and systems for tracking the location of devices near the surface of the Earth, and more particularly to a method and system for tracking a device near the surface of the Earth using a very fast acquisition portable transponder.
Various techniques are available to determine the position of a device on the surface of the Earth. U.S. Pat. No. 3,063,048 discloses the use of the Doppler shift in a transmitted signal to determine the position of a device transmitting the signal. This patent teaches measuring when the Doppler shift frequency was changing at a maximum rate to determine the position of the object transmitting the signal undergoing the Doppler frequency shift. In this system, the satellite must continuously receive the signal being transmitted from the object to determine when the frequency is changing at its maximum to locate the object. As a result, the time to compute a position fix is unacceptably long for applications such as locating a satellite telephone.
The Global Positioning System (GPS) also provides geo-location capability. Moreover, it is desirable know the position of a remote terminal, such as a cellular telephone, and to have this position information at a central location (e.g., at a Service Operations Center or SOC).
One technique is to place a GPS receiver on the remote terminal, calculate position in the GPS receiver, and transmit via satellite (or other communications system) the position fix to a central location. This method suffers from the Time-To-First-Fix (TTFF) limit inherent in GPS receivers upon waking up from a cold start. From the cold start state, a GPS receiver must download the GPS satellite almanac, ephemeris, and clock correction information. The TTFF limit effectively eliminates using a GPS receiver in situations where a long TTFF is unacceptable, such as in processing a telephone call from a wireless or cellular telephone.
The present invention is therefore directed to the problem of developing a system and method for calculating the position of a mobile terminal, which can be accomplished rapidly using a minimal amount of power and equipment.
SUMMARY OF THE INVENTION
The present invention solves this problem by collecting observation data at the mobile terminal, forwarding the observation data to a central location, and performing the position calculations at the central location rather than at the individual mobile terminal. Thus, the mobile terminal of the present invention needs only to gather a few milliseconds of observation data, such as GPS code phase information, and then relay this observation data to a central station, via satellite, for subsequent position calculation. In this manner, the present invention requires that the mobile unit be on only for very brief periods of time, so that a very fast (e.g. 1 second including data transmission time) position solution can be obtained. This would make practical, for example, the geolocation of a phone prior to a call being placed, which is particularly useful in satellite based phone services to control access and call routing decisions. The fast solution and minimal battery drain make practical the employment of a geolocating system in situations that may not otherwise economically justify such use.
According to one aspect of the present invention, a system for determining the location of an object located on or near the surface includes a communication satellite, a satellite gateway or earth station, a remote terminal, and an operations center. In this system, the communications satellite broadcasts an interrogation signal, to which the remote terminal responds. The remote terminal is disposed on the object, and includes a receiver, a transmitter and a processor. The receiver receives the interrogation signal from the communications satellite, and is capable of receiving signals being broadcast from GPS satellites. The processor measures at least one characteristic in each of the signals being broadcast from the GPS satellites upon receipt of the interrogation signal from the communications satellite. The remote terminal transmits a reply signal at a predetermined time relative to receipt of the interrogation signal to the communications satellite. The reply signal includes the measured characteristic(s) in each of the signals being broadcast from the plurality of GPS satellites. The operations center receives the reply signal from the communications satellite, and calculates a position of the remote terminal using time of arrival information and the measured characteristics returned by the remote terminal.
In the above system, the measured characteristic(s) can include, for example, code phase information, carrier phase information, Doppler-shift information, bit phase information, or Fourier transform coefficients.
The service operations center includes a processor calculating a range between the communications satellite and the remote terminal. In this calculation, the processor uses a time the reply signal arrived at the satellite gateway and a time difference between the broadcast of the interrogation signal to the remote terminal and its receipt at the satellite gateway. To do so, the processor accounts for known delays in the signal path between the communications satellite and the remote terminal and the point at which the time-of-arrival information is measured at the satellite gateway. The processor also calculates an intersection curve between a sphere, whose radius is the range previously determined, and a model of the surface of the Earth. Furthermore, the processor determines several initial points on the intersection curve, one of which points must lie within a known convergence zone around the terminal. Next, the processor calculates candidate position solutions for each initial point, and then screens the candidate solutions using predetermined criteria and discards any candidates not satisfying the screening. Finally, if more than one candidate solution remains, the processor selects the solution representing a best fit of all the observation data.
In the above system, the predetermined criteria may include one or more selected of the following: a solution range to the communications satellite, solution residuals, a solution altitude, a solution clock bias, and a solution proximity to a beam boundary.
REFERENCES:
patent: 4740792 (1988-04-01), Sagey et al.
patent: 4751512 (1988-06-01), Longaker
patent: 5043736 (1991-08-01), Darnell et al.
patent: 5202829 (1993-04-01), Geier
patent: 5223844 (1993-06-01), Mansell et al.
patent: 5225842 (1993-07-01), Brown et al.
patent: 5379224 (1995-01-01), Brown et al.
patent: 5444450 (1995-08-01), Olds et al.
patent: 5448623 (1995-09-01), Wiedeman et al.
patent: 5554993 (1996-09-01), Brickell
patent: 5587715 (1996-12-01), Lewis
patent: 5629707 (1997-05-01), Heuvel et al.
patent: 5758261 (1998-05-01), Wiedeman
patent: 5768266 (1998-06-01), Thompson et al.
patent: 5841398 (1998-11-01), Brock
patent: 5884142 (1999-03-01), Wiedeman et al.
patent: 5955986 (1999-09-01), Sullivan
patent: 5969669 (1999-10-01), Ishikawa et al.
patent: 5969673 (1999-10-01), Bickley et al.
patent: 6112054 (2000-08-01), Kita
Kilfeather James B.
Sullivan Mark C.
Cuchlinski Jr. William A.
Eagle Eye, Inc.
Pittman Shaw
To Tuan
LandOfFree
Fast acquisition position reporting system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fast acquisition position reporting system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fast acquisition position reporting system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2539171