Communications: directive radio wave systems and devices (e.g. – Directive – Including a satellite
Reexamination Certificate
1999-05-14
2001-03-27
Tarcza, Thomas H. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a satellite
C342S357490, C701S215000
Reexamination Certificate
active
06208289
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to global positioning systems (GPS) and even more particularly relates to differential GPS (DGPS).
BACKGROUND OF THE INVENTION
In the past, designers of avionics navigation systems have endeavored to provide systems with improved abilities to more precisely make location determinations using GPS satellites. One widely accepted approach to enhancing positional resolution for GPS receivers has been the use of differential GPS, which involves using a GPS receiver located at a known fixed location to generate pseudo range correction data, which then is provided to mobile receivers via a data link connection, where it is used to enhance the position determination abilities of the mobile receiver. This method is used widely in commercial airports throughout the world. When DGPS is used for commercial air carriers, it becomes necessary to have a very precise and robust DGPS system. A simple DGPS system provides much enhanced ability to determine position; however, the pseudo range computations made by a single DGPS receiver are not perfect. Numerous sources of errors still exist. Consequently, many airports are using an averaging technique to further reduce the errors present in a single DGPS receiver approach. These airports will place several DGPS receivers, each at a different surveyed location around the airfield, and calculate pseudo range correction data for each location. It is widely believed that many of the errors will be cancelled out and that an average of several, 5 or more, of the pseudo range corrections will be more precise than any single data set.
Another approach that has been used in the past has been to generate pseudo range correction data by a single GPS receiver and a single surveyed antenna.
While these DGPS stations have many advantages, they also have significant drawbacks.
First of all, for the multiple GPS receiver method, the cost of using five or more linked DGPS receivers and the computing equipment used to operate the system, can be very expensive. Secondly, for the multiple GPS receiver method, the position determined from such DGPS stations may have much improved precision. The situation may still exist that the pseudo range correction data sent to the mobile GPS receivers may result in a position determination that fails to meet the necessary precision requirements. For the single GPS receiver and single antenna method, the quality assessment of such a system is very limited, because using the same GPS receiver and the same antenna to confirm quality as to generate the data itself eliminates the ability of detecting errors which are resulting from the receiver and antenna themselves. Consequently, there exists a need for improvement in systems and methods for monitoring and reporting pseudo range correction data.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide enhanced pseudo range correction information.
It is a feature of the present invention to utilize a second GPS receiver at a second known location for using pseudo range correction data produced by a first surveyed GPS receiver at another location.
It is an advantage of the present invention to better determine the quality of the pseudo range correction data being generated by a DGPS station.
It is another feature of the present invention to include a pseudo range data buffer and position error comparison function to determine before transmitting to mobile receivers, if the pseudo range correction data being generated results in a position determination which is within a predetermined acceptable range.
It is another advantage of the present invention to reduce the potential for transmitting pseudo range correction data to an aircraft which would result in a position determination not within the acceptable range.
The present invention is an apparatus and method monitoring and reporting pseudo range correction data for GPS receivers which is designed to satisfy the aforementioned needs, provide the previously stated objects, include the above-listed features and achieve the already articulated advantages. The present invention is carried out in a “high integrity data correction system” in a sense that the uncertainty of the level of quality of the pseudo range correction data being transmitted to mobile receiver has been greatly reduced.
Accordingly, the present invention is a system and method for monitoring and reporting pseudo range correction data to mobile GPS receivers, where the system and method involves using a second GPS receiver at a known location to use pseudo range correction data, generated by a first GPS receiver and antenna, to generate an enhanced position determination and further involves making a determination of the quality of the pseudo range correction data generated by the first GPS receiver, by a comparison of the surveyed position of the second GPS receiving antenna with the enhanced position determination calculated by the second GPS receiver using the pseudo range correction data provided by the first GPS receiver.
REFERENCES:
patent: 5436632 (1995-07-01), Sheynblat
patent: 5523761 (1996-06-01), Gildea
patent: 5589835 (1996-12-01), Gildea et al.
patent: 5796365 (1998-08-01), Lewis
patent: 5999878 (1999-12-01), Hanson et al.
Eppele Kyle
Jensen Nathan O.
O'Shaughnessy J. P.
Phan Dao L.
Rockwell Collins, Inc.
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