GPS receiving system

• US 6,480,787 B2
• Filed: 07/13/2001
• Issued: 11/12/2002
• Est. Priority Date: 09/12/2000
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Yamada, Katsuhiko, Yoshikawa, Shoji, Tsukui, Jun
• Primary Examiner(s): Beaulieu, Yonel
• Application Number:
  US09/903,744
• Publication Number:
  US 20020032525A1
• Time in Patent Office: 487 Days
• Field of Search: 701/200, 701/213, 701/214, 701/215, 701/216, 342/357.06, 342/357.12, 342/357.03
• US Class Current: 701/213
• CPC Class Codes: B64G 1/36 using sensors, e.g. sun-sensors, horizon sensors
• CPC Class Codes: G01S 19/23 Testing, monitoring, correcting or calibrating of receiver elements
• CPC Class Codes: G01S 19/51 Relative positioning
• CPC Class Codes: G01S 19/52 Determining velocity
• CPC Class Codes: G01S 5/0072 Transmission between mobile stations, e.g. anti-collision systems

Abstract

A global positioning system (GPS) receiving system which achieves an equivalent synchronization in time measurement of GPS signals utilizing software without requiring highly accurate synchronization for receiver clocks with time information embedded in the GPS signals. The GPS receiving system performs a relative navigation process after correcting a pseudorange with a time tag error which is attributable to inaccuracy of receiver clocks of first and second moving objects. A relative navigation process correcting an absolute error of a time tag with a clock bias is also described. A differential computation unit calculates a difference between the first pseudorange and the second pseudorange commonized by the time tag commonizing unit. Correction in a time tag error correction unit is performed for the selected GPS data with a common GPS satellite identification number.

Claims

1. A global positioning system (GPS) receiving system having a first GPS receiver mounted on a first moving object and a second GPS receiver mounted on a second moving object, the first and second GPS receivers calculating relative positions and relative velocities of the first and second moving objects by selecting GPS data with a common GPS satellite identification number from first GPS data yielded by the first GPS receiver and second GPS data yielded by the second GPS receiver, at least one of the first moving object and the second moving object comprising:

a time tag commonizing unit for commonizing time tags of a first pseudorange between a GPS satellite and the first moving object and a second pseudorange between the GPS satellite and the second moving object;

a differential computation unit for calculating a difference between the first pseudorange and the second pseudorange commonized by the time tag commonizing unit; and

a time tag error correction unit for correcting the difference with a time tag error attributable to clock inaccuracy of the first GPS receiver and the second GPS receiver.

2. The GPS receiving system according to claim 1, wherein the time tag error correction unit calculates the time tag error from (a) a first range rate, which is a change rate of the first pseudorange, (b) a first clock bias, which is clock inaccuracy of the first GPS receiver, (c) a second range rate, which is a change rate of the second pseudorange, and (d) a second clock bias, which is clock inaccuracy of the second GPS receiver.

3. The A GPS receiving system according to claim 1, comprising:

a first absolute navigation unit for estimating a first clock bias from an output of the first GPS receiver;

a first range rate calculation unit for calculating a first range rate from the output of the first GPS receiver;

a second absolute navigation unit for estimating a second clock bias from an output of the second GPS receiver; and

a second range rate calculation unit for calculating a second range rate from the output of the second GPS receiver, wherein the time tag error correction unit calculates a time tag error from the first clock bias and the second clock bias respectively estimated by the first absolute navigation unit and the second absolute navigation unit, and the first range rate and the second range rate respectively calculated by the first range rate calculation unit and the second range rate calculation unit.

4. The A GPS receiving system according to claim 1, wherein the time tag error correction unit calculates the time tag error from a relative clock bias, the relative clock bias being a difference between the first clock bias and the second clock bias, and one of the first and second range rates.

5. The A GPS receiving system according to claim 4, comprising a relative navigation unit for receiving an output of the time tag error correction unit and for calculating relative positions and relative velocities of the first and second moving objects, wherein the time tag error correction unit uses the relative clock bias yielded by the relative navigation unit.

6. The A GPS receiving system according to claim 1, wherein the time tag error correction unit calculates the time tag error from the difference and one of the first and second range rates.

7. A global positioning system (GPS) receiving system having a first GPS receiver mounted on a first moving object and a second GPS receiver mounted on a second moving object, the first and second GPS receivers calculating relative positions and relative velocities of the first and second moving objects by selecting GPS data with a common GPS satellite identification number from first GPS data yielded by the first GPS receiver and second GPS data yielded by the second GPS receiver, at least one of the first moving object and the second moving object comprising:

a time tag error correction unit for correcting a time tag of the GPS data selected for a clock bias, which is clock inaccuracy of the GPS receiver producing the GPS data selected;

a time tag commonizing unit for commonizing a time tag of the GPS data selected and which has been corrected by the time tag error correction unit; and

a differential computation unit for calculating a difference between a first pseudorange and a second pseudorange having time tags that have been commonized by the time tag commonizing unit.

8. The GPS receiving system according to claim 7, comprising:

a first absolute navigation unit for estimating a first clock bias, which is the clock bias of the first GPS receiver from an output of the first GPS receiver; and

a second absolute navigation unit for estimating a second clock bias, which is the clock bias of the second GPS receiver from an output of the second GPS receiver, wherein the time tag error correction unit uses the first clock bias estimated by the first absolute navigation unit and the second clock bias estimated by the second absolute navigation unit.

9. A global positioning system (GPS) receiving system comprising:

a first GPS receiver obtaining GPS data from a plurality of GPS satellites and communicating with a second GPS receiver;

a common GPS satellite selection unit for selecting GPS data required for determining a relative distance between the first GPS receiver and the second GPS receiver from a plurality of GPS data obtained by the first GPS receiver from the plurality of satellites;

a time tag commonizing unit for commonizing time tags of the first GPS receiver and the second GPS receiver with regard to the GPS data selected;

a differential computation unit for calculating a difference between commonized GPS data of the first GPS receiver and commonized GPS data of the second GPS receiver;

a time tag error correction unit for correcting the difference calculated with an error based on clock inaccuracy between the first GPS receiver and the second GPS receiver; and

a relative navigation unit for determining relative positions of the first GPS receiver with respect to the second GPS receiver based on the calculated difference after correction.

10. A global positioning system (GPS) receiving system comprising:

a first GPS receiver obtaining GPS data from a plurality of GPS satellites and communicating with a second GPS receiver;

a common GPS satellite selection unit for selecting GPS data required for determining a relative distance between the first GPS receiver and the second GPS receiver from a plurality of items of GPS data obtained by the first GPS receiver from the plurality of satellites;

a time tag error correction unit for correcting time tags of the GPS data selected using clock inaccuracy between the first GPS receiver and the second GPS receiver;

a time tag commonizing unit for commonizing corrected time tags of the first GPS receiver and the second GPS receiver, after correction, for each item of the GPS data selected;

a differential computation unit for calculating a difference between commonized GPS data of the first GPS receiver and commonized GPS data of the second GPS receiver; and

a relative navigation unit for determining relative positions of the first GPS receiver with respect to the second GPS receiver based on the calculated difference.