Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2002-05-06
2004-08-31
Nguyen, Tan Q. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S207000, C340S988000
Reexamination Certificate
active
06785609
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a hybrid processing method and apparatus. In the hybrid processing method, a self-contained or built-in positioning method using a vehicle speed sensor, a gyro sensor or the like, is combined with a GPS (Global Positioning System) method of positioning or measuring a current position of a movable body on the basis of radio waves from GPS satellites. Similarly, in the hybrid processing apparatus, a self-contained or built-in positioning apparatus using a vehicle speed sensor, a gyro sensor or the like, is combined with a GPS apparatus. The present invention also relates to a navigation system including the above-mentioned hybrid processing apparatus, a program storage device and a computer data signal embodiment in a carrier wave, which allow a computer to function as the hybrid processing apparatus.
2. Description of the Related Art
Nowadays a navigation system of a movable body such as a vehicle, an airplane, a ship or the like generally performs various types of hybrid processing, in which the self-contained positioning measurement using a vehicle speed sensor, a gyro sensor or the like, is combined with the GPS measurement in one way or another.
For example, Japanese Patent Application Laying Open NO. Hei 10-307036 discloses such a technique that an error correction is performed with respect to acceleration data, drive distance data, advance azimuth data or the like as self-contained positioning data, on the basis of GPS measurement.
Moreover, as for the GPS measurement, a current position is calculated independently, for example, every one or two seconds. Thus, there is such a technique to estimate or predict the current position, which is to be calculated next time i.e., for the n+1-th time, by virtue of a Kalman filter, a position filter or the like with using the current position calculated this time i.e., for the n-th time as a standard, and to thereby perform an error correction based on this estimated or predicted position with respect to the current position, which is actually calculated for the n+1-th time. Accordingly, the corrected current position can be calculated with a higher accuracy.
By the way, the radio wave from the GPS satellite may have other paths to go through to the GPS receiver after reflecting on the surface of a huge building or the like once or more times, in addition to the path to go direct to the GPS receiver, especially around the huge building such as a skyscraper, a high-rise building, or the like. This phenomenon, under which the radio waves are received at the same time through a plurality of radio wave paths from the one identical GPS satellite, is called as a “multi-path”. When the multi-path in this kind is generated, the accuracy of the GPS measurement deteriorates. Namely, the GPS measurement has such a disadvantage that the generation of the multi-path certainly deteriorates a positioning accuracy.
On the other hand, as for a self-contained sensor such as a gyro sensor or the like as described above, it has a big start drift when switching on a power. Then, if, for example, the start drift of a gyro sensor occurs, an angle is calculated with deviation. Therefore, a specification of a gyro sensor or the like describes that the error of its output increases for a predetermined period such as 10 min or 15 min after starting. Consequently, there is concern that the accuracy of the GPS measurement deteriorates more if the output of the self-contained sensor is reflected to the GPS measurement within this predetermined period after starting.
However, there is such a problem that, if the accuracy of the GPS measurement deteriorates by the generation of the multi-path as described above for 10 min or 15 min after starting, the positioning accuracy by the hybrid based on the GPS measurement data deteriorates similarly.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a hybrid processing method and apparatus, which can measure a position with a relatively high accuracy after starting including just after starting a navigation system, an on-vehicle navigation system including the above-mentioned hybrid processing apparatus, as well as a program storage device and a computer data signal embodiment in a carrier wave, which allow a computer to function as the hybrid processing apparatus.
The above object of the present invention can be achieved by a hybrid processing method of outputting current position data, which indicate a current position of a movable body on which a self-contained positioning device and a GPS device are mounted, on the basis of self-contained positioning data from the self-contained positioning device and GPS measurement data from the GPS device, the method provided with: a judgment process of judging whether or not an estimated error of the self-contained positioning data is greater than a predetermined threshold value; a first calculation process of calculating the current position by combining the GPS measurement data with the self-contained positioning data if the estimated error is judged not greater than the predetermined threshold value; a second calculation process of calculating the current position from the GPS measurement data without combining the GPS measurement data with the self-contained positioning data if the estimated error is judged greater than the predetermined threshold value; and an output process of outputting the current position calculated by the first or second calculation process as the current position data which indicate the current position of the movable body.
According to the hybrid processing method of the present invention, such a judgment is performed by a judgment process that whether or not an estimated or predicted error of the self-contained positioning data is greater than a predetermined threshold value. This kind of estimated or predicted error may be calculated by the self-contained positioning device and may be outputted together with the self-contained positioning data. Alternatively, it may be calculated on the basis of the self-contained positioning data outputted from the self-contained positioning device. The predetermined threshold value is individually and concretely determined depending on the each specification of the self-contained positioning devices or the like experientially, experimentally, theoretically, or simulationally etc. It may be a fixed value or a variable value depending on an actual operational condition. Then, the current position is calculated by the first calculation process by combining the GPS measurement data with the self-contained positioning data if the estimated error is judged not greater than the predetermined threshold value. Namely, if the estimated error is to some degree small even after starting the navigation system, including just after starting the navigation system, the start drift of the self-contained positioning data is relatively minor. Accordingly, when combining the self-contained positioning data with the GPS measurement data, the action or effect of restraining the accuracy deterioration due to the multi-path etc., in the GPS measurement data by virtue of the self-contained positioning data becomes superior to the action or effect of deteriorating the measurement accuracy due to the start drift. Therefore, in this case, it can effectively prevent the accuracy of such a finally outputted current position from being degraded due to the deterioration of the GPS measurement accuracy by the multi-path or the like by calculating the corrected current position as combining the GPS measurement data with the self-contained positioning data in the first calculation process.
On the other hand, the current position is calculated by the second calculation process by the GPS measurement data without combining the GPS measurement data with the self-contained positioning data if the estimated error is judged greater than the predetermined threshold value. Namely, if the estimated error is to some
Morgan & Lewis & Bockius, LLP
Nguyen Tan Q.
Pioneer Corporation
Tran Dalena
LandOfFree
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