Position measuring system
First Claim
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1. A position measuring system for a vehicle comprising:
- means for detecting navigational data by receiving radio waves emitted by satellites;
switching means having a change-over switch connected to said detecting means;
first computing means connected to the change-over switch for computing initial estimated values of the vehicle'"'"'s position on the basis of the navigational data when said change-over switch is in a first position;
memory means for storing the initial estimated values calculated in the first computing means; and
second computing means connected to said change-over switch and said memory means for convergently computing the true position of the vehicle based on the initial estimated values and the navigational data when said change-over switch is in a second position, wherein said first position indicates that the initial estimated values have not been stored in said memory means and said second position indicates that the initial estimated values have been stored in said memory means.
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Abstract
An improved position measuring system for determining a vehicle'"'"'s position by receiving radio waves emitted from satellites is shown. The system adopts successive approximation using a convergent computation, in which initially estimated values are computed.
24 Citations
7 Claims
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1. A position measuring system for a vehicle comprising:
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means for detecting navigational data by receiving radio waves emitted by satellites; switching means having a change-over switch connected to said detecting means; first computing means connected to the change-over switch for computing initial estimated values of the vehicle'"'"'s position on the basis of the navigational data when said change-over switch is in a first position; memory means for storing the initial estimated values calculated in the first computing means; and second computing means connected to said change-over switch and said memory means for convergently computing the true position of the vehicle based on the initial estimated values and the navigational data when said change-over switch is in a second position, wherein said first position indicates that the initial estimated values have not been stored in said memory means and said second position indicates that the initial estimated values have been stored in said memory means. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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4. A position measuring system as claimed in claim 1, wherein the estimated value is repeatedly computed by the equation, ##EQU20## wherein X, Y, Z:
- coordinates corresponding to the position of the vehicle
Xi, Yi, Zi ;
coordinates corresponding to the position of the satellitesKi ;
sum of the radius of the earth and the distance between the satellite and the center of the earthδ
T;
deviation in the clock of the systemRi '"'"';
measured distance between the satellite and the vehicleC;
speed of lightε
;
an error.
- coordinates corresponding to the position of the vehicle
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5. A position measuring system as claimed in claim 4, wherein the estimated values are repeatedly computed until they satisfy the inequality equation ##EQU21## and until it is determined whether a new offset time δ
- T is within a tolerable range wherein Ro is the radius of the earth.
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6. A position measuring system as claimed in claim 3, wherein the estimated coordinates X, Y and Z are multiplied by a weight factor k so that kX, kY and kZ form corrected coordinates of the vehicle.
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7. A position measuring system as claimed in claim 1, further comprising a route guiding unit connected to the second computing means for receiving a signal therefrom and connected to the memory means for outputting thereto a signal indicating the present position for the vehicle, thereby guiding the path of the vehicle.
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Specification