Method and apparatus for improving the accuracy of position estimates in a satellite based navigation system using velocity data from an inertial reference unit

• US 5,606,506 A
• Filed: 04/05/1993
• Issued: 02/25/1997
• Est. Priority Date: 04/05/1993
• Status: Expired due to Term

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Kyrtsos, Christos T.
• Primary Examiner(s): Chin, Gary
• Application Number:
  US08/042,738
• Time in Patent Office: 1,422 Days
• Field of Search: 364/443, 364/444, 364/449, 364/453, 364/454, 364/459, 73/178 R, 340/988, 340/990, 342/451, 342/457, 342/357, 342/358
• US Class Current: 701/207
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01S 19/47 the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial

Abstract

A method and apparatus for computing a precise position estimate for a receiver at or near the surface of the Earth uses a inertial reference unit associated with the receiver and a satellite-based navigation system. The satellite-based navigation system is used to determine a position estimate for the receiver at consecutive positions along its path of motion. The inertial reference unit is used to determine velocity vectors for the receiver. Each velocity vector corresponds to travel of the receiver between the consecutive positions. The velocity vectors from the inertial reference unit are used to refine the position estimates of the satellite-based navigation system to obtain precise position estimates.

Claims

1. A method for computing a precise position estimate for a receiver at or near the surface of the Earth using an inertial reference unit associated with the receiver and a satellite-based navigation system including a constellation of navigation satellites, the method comprising the steps of:

(a) receiving, from the constellation of navigation satellites, navigation signals at the receiver located at a first position at a first time;

(b) computing, from said plurality of navigation signals, a first position estimate for the receiver at said first time, said first position estimate representing a single point at or near the surface of the Earth;

(c) moving the receiver to a second position at a second time;

(d) receiving, from the constellation of navigation satellites, navigation signals at the receiver located at said second position at second time;

(e) computing, from said navigation signals, a second position estimate for the receiver at said second time, said second position estimate representing a single point at or near the surface of the Earth;

(f) receiving a velocity vector from the inertial reference unit for the elapsed time between said first time and said second time; and

(g) computing a refined value for said second position estimate based on said first position estimate, said second position estimate, said velocity vector and said elapsed time.

2. An apparatus for computing a precise position estimate for a vehicle moving on or near the surface of the Earth using a satellite-based navigation system including a constellation of navigation satellites, the apparatus comprising:

(a) receiver means, coupled to the vehicle, for receiving navigation signals from the constellation of navigation satellites and for computing a first position estimate for a first vehicle position at a first time, a second position estimate for a second vehicle position at a second time, and a third position estimate for a third vehicle position at a third time, each of said first, second and third position estimates representing a single point at or near the surface of the Earth;

(b) inertial means, coupled to the vehicle, for computing a first velocity vector of the vehicle for the period between said first and second times and for computing a second velocity vector of the vehicle for the period between said second and third times; and

(c) processing means for refining said third position estimate based on said first, second and third position estimates, said first and second velocity vectors and said first, second and third times.

3. A method for determining a position of a receiver at or near the surface of the Earth using an inertial reference unit coupled to the receiver and a satellite-based navigation system including a constellation of navigation satellites, the method comprising the steps of:

(a) receiving, from the constellation of navigation satellites, navigation signals at the receiver located at a first position at a first time;

(b) computing, from said plurality of navigation signals, a first position estimate for the receiver at said first time, said first position estimate representing a single point at or near the surface of the Earth;

(c) moving the receiver to a second position at a second time;

(d) receiving, from the constellation of navigation satellites, navigation signals at the receiver located at said second position at second time;

(e) computing, from said navigation signals, a second position estimate for the receiver at said second time, said second position estimate representing a single point at or near the surface of the Earth;

(f) receiving a first velocity vector from the inertial reference unit for the elapsed time between said first time and said second time;

(g) moving the receiver to a third position at a third time;

(h) receiving, from the constellation of navigation satellites, navigation signals at the receiver located at a third position at a third time;

(i) computing, from said plurality of navigation signals, a third position estimate for the receiver at said third time, said third position estimate representing a single point at or near the surface of the Earth;

(j) receiving a second velocity vector from the inertial reference unit for the elapsed time between said second time and said third time; and

(k) computing a refined value for said third position estimate based on said first, second and third position estimates, said first and second velocity vectors and said elapsed times.