Near-real time DGPS network and server system

Details Near-real time DGPS network and server system Near-real time DGPS network and server system

1998-11-05

2001-05-08

Blum, Theodore M. (Department: 3662)

Communications: directive radio wave systems and devices (e.g.,

Directive

Including a satellite

C342S357490, C342S357490, C701S215000

Reexamination Certificate

active

06229478

ABSTRACT:

TECHNICAL FIELD
The present invention relates to position location systems. In particular, the present invention pertains to a networked position location system.
BACKGROUND ART
Position determination devices, such as hand-held GPS (global position system) receivers are widely used and well known in the art. Such devices typically receive signals from a plurality of GPS satellites, perform complex measurements on the received signals, and analyze various other information received from the satellites (e.g. ephemeris data). These steps are performed by conventional position determination devices in order to compute the location of the position determination device. It will be understood that in order to perform the aforementioned complex measurements and signal analyses, a conventional position determination device must have sophisticated hardware and system components. The sophisticated hardware and system components are a source of significant cost in such position determination devices.
In addition to having each position determination device operate independently, some prior art approaches employ a networked system. In a conventional networked system, typically each position determination device (sometimes referred to as a rover unit) is coupled to a central base. In many instances, the user of the rover units may subscribe to or pay a fee to access the networked system. Upon computing their respective positions, the numerous position determination devices or rover units report their position to the central base. As a result, the central base (e.g. a dispatch station) is aware of the respective locations of the various rover units. The position information of the rover units is often made available to the other rover units via the central base. In such a networked system, the number of rover units can vary widely. For example, a large percentage or a small percentage of the eligible or subscribing rover units may be accessing the system at a given time. Additionally, the networked system may periodically be receiving new subscribers. That is, a new user may purchase a new rover unit and then attempt to utilize the networked system.
One prior art example of networked system is described in U.S. Pat. No. 5,663,734 to Krasner, entitled “GPS Receiver and Method for Processing GPS Signals.” The Krasner reference illustrates several of the disadvantages associated with prior art networked systems. For example, the base station commands or directs the remote unit to perform various functions, such as reporting the remote unit's location to the base station. As a result, a considerable processing and control burden is placed on the base station. Additionally, in the Krasner system, the maximal range that the remote unit can extend from the base station is limited to approximately ½ the speed of light times the PRN (pseudo-random noise) repetition period (1 millisecond). This distance is calculated to be approximately 150 kilometers. The relatively short maximal range limits the usefulness of conventional networked systems such as the system of the Krasner reference. That is, operation of the rover units is restricted to only a limited distance from the base station.
Another drawback, during normal use (e.g. when first turned-on) a conventional position determination device/rover unit undergoes a time-consuming initialization process. During this process, the rover unit gathers substantial initialization data from the GPS satellites. The initialization data is required for the position determination device to be operable and in condition to determine position information. Additionally, the initialization process is often confusing to the average consumer. The drawbacks associated with a conventional time-consuming initialization process are further compounded in a networked system due to the constant addition of new subscribing rover units to the network. That is, each of multiple new subscribing rover units has to be completely initialized before use, and multiple new users are often confused by the initialization process.
In addition to the aforementioned drawbacks, a rover unit must be very inexpensive in order for the rover unit to be attractive to and affordable for the average consumer. Therefore, it is not commercially feasible to attempt to resolve any of the aforementioned drawbacks by significantly increasing the complexity, and, correspondingly, the cost of the system and hardware components of the rover unit. Previous self-contained GPS receivers could do everything necessary to obtain a position fix, but at significant expense. It would be desirable to reduce the costs of obtaining position in a device that already includes a communications system.
Thus, a need has arisen for a method and system for improving the operation of a rover unit in a networked system. Moreover, a need exists for a method and system for improving the operation of a rover unit in a networked system without significantly increasing the system and hardware requirements of the rover unit.
DISCLOSURE OF THE INVENTION
The present invention provides a method and system for improving the operation of a rover unit in a networked system. Moreover, the present invention provides a method and system for improving the operation of a rover unit in a networked system without significantly increasing the system and hardware requirements of the rover unit. In one embodiment, the present invention provides a method and system for rapidly initializing a rover unit. In this embodiment, the present invention acquires rover unit initialization data at a reference station. In this embodiment, the rover unit initialization data is selected from the group consisting of: ephemeris data, almanac data, satellite health data, ionospheric model data, and GPS and UTC time information, and approximate position. In the present embodiment, the present invention then communicatively couples the reference station to a server station having memory for storing the rover unit initialization data. After communicatively coupling the reference station to the server station, the present embodiment transfers the rover unit initialization data from the reference station to the server station. The present embodiment then communicatively couples the rover unit to the server station. Next, the present embodiment supplies the rover unit initialization data from the server station to the rover unit. As a result, in the present embodiment, the rover unit is able to be initialized and obtain a first position fix without requiring the rover unit to acquire the initialization data directly from at least one satellite.
In another embodiment, the present invention provides a method and system for providing differentially corrected position information to a rover unit. In this embodiment the server station includes a differential correction engine for differentially correcting position information when requested. The reference station, which is communicatively coupleable to the server station, provides differential correction data to the server station such that the server station is able to utilize the differential correction data when differentially correcting position information. The rover unit, which is also communicatively coupleable to the server station, has a position generation engine for providing position information of the rover unit. When desired, the rover unit forwards its position information to the server station and requests the server station to differentially correct the position information of the rover unit and return differentially corrected position information of the rover unit to the rover unit. As a result, in the present embodiment, the rover unit is able to acquire differentially corrected position information upon demand without requiring the rover unit to have a differential correction engine integral therewith.
In still another embodiment, the present invention includes the features of both of the above-described embodiments. That is, in the present embodiment, the present invention provides a method and

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