Apparatus for verifying GPS satellite data

• US 5,631,838 A
• Filed: 03/11/1996
• Issued: 05/20/1997
• Est. Priority Date: 08/02/1993
• Status: Expired due to Fees

• Current Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.)
• Original Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.)
• Inventors: Ishikawa, Seiji, Murakami, Yuichi, Yamamoto, Tomohiro, Oka, Toshimitsu, Yasuda, Tomio
• Primary Examiner(s): Teska, Kevin J.
• Assistant Examiner(s): WALDER, STEPHEN JOSEPH
• Application Number:
  US08/614,941
• Time in Patent Office: 435 Days
• Field of Search: 364/434, 364/454, 364/459, 364/443, 364/449, 364/453, 244/176, 342/357
• US Class Current: 701/215
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment

Abstract

A length of time required for the verification of data transmitted from a satellite or satellites is reduced. A distance r1 calculated from a time delay required for the propagation of a radio wave between a transmitting and a receiving site is obtained, as is a line-of-sight distance r2 which is calculated from the positions of a satellite and a point of reception. When a difference between these two distances is small, data from these satellites are regarded as valid data. However, when the difference is large, data is regarded as involving a large error. The position of the point of reception is determined by a positioning calculation which utilizes data from predetermined three or four verified satellites, or is entered by an operator. The position of the satellite is obtained from orbital data which is delivered by that satellite.

Claims

1. An apparatus for verifying global positioning system (GPS) satellite data and registering GPS satellites as verified, comprising:

receiver means for receiving information from a plurality of GPS satellites each of which delivers information relating to its own orbit and timing thereof;

positioning calculation means for calculating the position of a point of reception based on information received by said receiver means from the plurality of GPS satellites;

verified position determining means for determining a verified position of the point of reception based on information from at least three GPS satellites registered as available;

first distance calculating means for calculating a distance between an unverified GPS satellite and the point of reception based on positional information of the unverified GPS satellite which is determined from the received orbital information and from information relating to the verified position of the point of reception determined by said verified position determining means;

second distance calculating means for determining a time delay required for the propagation of information delivered from the unverified GPS satellite to the point of reception based on received timing information and the point in time when such timing information is received, and for calculating a distance between the unverified GPS satellite and the point of reception from such time delay;

first verifying means for verifying data of four or more GPS satellites, registering the four or more GPS satellites as verified and setting a verification flag, wherein said first verification means determines a plurality of positions of the point of reception based on combinations of three of four or more entities of information received from the four or more GPS satellites, said first verification means calculates differences between said plurality of positions, compares the differences with a first predetermined threshold, and registers the four or more satellites as verified and sets the verification flag if the differences are smaller than the first predetermined threshold, wherein said first verifying means operates if the verification flag is not set; and

second verifying means for determining a difference between the distance determined by the first distance calculating means and the distance determined by the second distance calculating means, and for registering the unverified GPS satellite as one which is available for use in the calculation by the positioning calculation means whenever the difference is less than a second predetermined threshold and for registering the unverified GPS satellite as unavailable for use in the calculation by the positioning calculation means whenever the difference is greater than the second predetermined threshold, wherein said second verifying means operates when the verification flag is set.

2. An apparatus according to claim 1, wherein said second distance calculating means saves timing information contained in information delivered from the unverified GPS satellite whenever such timing information is detected, and then waits for the appearance of the leading end of a next subframe of such information, and upon detection of the leading end of the next subframe, calculates the time delay required for propagation of the timing information based on a difference between the point in time of reception of the leading end of the next subframe and the saved timing information.

3. An apparatus for verifying GPS satellite data comprising:

receiver means for receiving information from a plurality of GPS satellites each of which delivers information relating to its own orbit and timing thereof;

positioning calculation means for calculating the position of a point of reception based on information received by the receiver means from the plurality of GPS satellites;

verified position determining means for determining a verified position of the point of reception based on information received from at least three GPS satellites registered as available;

first distance calculating means for calculating a distance between an unverified GPS satellite and the point of reception based on positional information of the unverified GPS satellite determined from the received orbital information and information relating to the verified position of the point of reception determined by said verified position determining means;

second distance calculating means for determining a time delay required for propagation of information delivered from the unverified GPS satellite received at the point of reception based on received timing information and the point in time when such timing information is received, and calculating a distance between the unverified GPS satellite and the point of reception from the determined time delay;

verifying means for determining a difference between the distance determined by the first distance calculating means and the distance determined by the second distance calculating means, and registering the unverified GPS satellite as one which is available for use in the calculation by the positioning calculation means whenever the difference is less than a predetermined threshold and registering the unverified GPS satellite as unavailable for use in the calculation by the positioning calculation means whenever the difference is greater than the predetermined threshold, wherein said verifying means operates when a verification flag is set; and

auxiliary verifying means for obtaining a plurality of positions of the point of reception based on combinations of three entities chosen from among four entities of information received from four GPS satellites, comparing a difference between any two of the plurality of positions with the threshold value, for determining whether the four GPS satellites are available for use in the calculation of the positioning calculation means, registering the four GPS satellites as available, and setting the verification flag, wherein said verifying means verifies remaining GPS satellites which are not registered as available after the four GPS satellites are registered as available by the auxiliary verifying means.

4. A method for verifying data from a satellite among a first plurality of satellites each of which transmits a signal, the method comprising the steps of:

a) receiving at a point of reception the signals transmitted from the first plurality of satellites and based on the received signals determining a position of the point of reception;

b) verifying data transmitted by each satellite of a second plurality of satellites, wherein each of said second plurality of satellites is included in the first plurality of satellites, wherein step b) comprises the steps of;

b1) performing satellite positioning calculations based on said second plurality of satellites thereby determining a plurality of positions;

b2) computing differences between said plurality of positions and comparing the differences with a first predetermined threshold value; and

b3) registering as verified each of said second plurality of satellites if the differences computed in step b2) do not exceed the first predetermined threshold value;

c) selecting one of the first plurality of satellites which is not one of said second plurality of satellites, and verifying the data transmitted by the selected satellite, wherein step c) comprises the steps of;

c1) measuring a distance between the point of reception and the selected satellite, based on a time delay of the selected satellite signal;

c2) calculating a line-of-sight distance between the selected satellite and the position of the point of reception; and

c3) comparing the range measured in step c1) with the line-of-sight distance calculated in step c2) and registering the selected satellite as verified if the comparison is less than a second predetermined threshold value; and

d) repeating step c) when another one of the first plurality of satellites is selected which is not registered as verified.

5. The method recited in claim 4, wherein said first plurality of satellites are global positioning system (GPS) satellites.

6. The method recited in claim 4, wherein said second predetermined threshold value is 10 kilometers.

7. The method recited in claim 4, wherein the position of the point of reception is not accurately known prior to performing step a).

8. The method recited in claim 4, wherein in step b1) each one of the plurality of positions corresponds to a position of the point of reception calculated for a combination of the satellites of the second plurality of satellites.

9. The method recited in claim 4, wherein the second plurality of satellites consists of four or more satellites.

10. The method recited in claim 4, wherein the data from the selected satellite includes orbital information relating to a position of the selected satellite, and the line-of-sight distance calculated in step c2) is calculated based on the orbital information from the selected satellite and the previously determined position of the point of reception.

11. The method recited in claim 10, wherein said line-of-sight distance calculated in step c2) is represented by variable r2, where ##EQU1## such that the orbital information from the selected satellite is represented in three-dimensions by variables Sx, Sy, Sz and the position of the point of reception is represented in three-dimensions by variables Ux, Uy, Uz.