Correcting GPS position in a hybrid naviation system

• US 5,394,333 A
• Filed: 12/20/1993
• Issued: 02/28/1995
• Est. Priority Date: 12/23/1991
• Status: Expired due to Term

• Current Assignee: TomTom International BV (TomTom NV)
• Original Assignee: Zexel USA Corporation
• Inventors: Kao, Wei-Wen
• Primary Examiner(s): Teska, Kevin J.
• Assistant Examiner(s): LOUIS JACQUES, JACQUES H
• Application Number:
  US08/170,405
• Time in Patent Office: 435 Days
• Field of Search: 364/424.02, 364/424.05, 364/424.01, 364/444, 364/436, 364/456, 364/450, 364/449, 364/453, 364/454, 364/457, 342/357, 342/457, 340/990, 340/995
• US Class Current: 701/217
• CPC Class Codes: G01C 21/30 Map- or contour-matching
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude
• CPC Class Codes: G01S 19/47 the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial

Abstract

A hybrid vehicle navigation system employs both GPS and dead reckoning sensors, working in parallel, to produce a sensed and a calculated position, respectively. The sensed and the calculated positions are compared to a road data base to determine separate correction factors required to correct the sensed and the calculated positions. In one embodiment, the system employs either the sensed or calculated position for navigation depending on which has the smaller correction factor.

Claims

1. A hybrid vehicle navigation system comprising:

means for determining a sensed position of said vehicle from a Global Positioning System;

means for determining a calculated position of said vehicle from at least one dead reckoning sensor;

means for comparing said sensed vehicle position and said calculated vehicle position with a location selected from a plurality of candidate vehicle positions in a map database containing pre-stored locations obtained from an external system;

means for computing a plurality of correction factors, one for each sensed position and one for each calculated position;

said means for computing being effective for choosing one of said plurality of correction factors that, when used to correct said vehicle position, makes said vehicle position correspond to said location; and

means, based on said selected correction factor and an associated one of said sensed position and said calculated position, for correcting said vehicle position.

2. Apparatus according to claim 1, wherein said means for comparing is a microcomputer.

3. A hybrid vehicle navigation system as in claim 1, wherein a means is provided to further improve a reliability of said system by performing sequential iterations with decreasing increments in said correction factor, minimizing an error in matching one of said sensed position and calculated position to said selected map database location.

4. A method for improving the reliability of a vehicle position determined from the Global Positioning System which comprises the steps of:

determining a sensed vehicle position from a Global Positioning System;

determining a calculated vehicle position from at least one dead reckoning sensor;

comparing said sensed vehicle position and said calculated vehicle position with a location selected from a plurality of vehicle positions in a map database containing pre-stored locations obtained from an external system;

computing a plurality of correction factors, one for each sensed position and one for each calculated position; and

selecting from said plurality one correction factor that, when used, makes a corrected vehicle position correspond to said location.

5. Apparatus for improving the reliability of a vehicle position determined from the Global Positioning System, which comprises:

a Global Positioning System receiver for receiving signals from transmitters of a Global Positioning System;

dead reckoning sensors for determining calculated positions;

means for transforming said signals into said sensed vehicle position and outputs from said sensors into said calculated vehicle position respectively;

said means for transforming further including means for comparing said sensed vehicle position and said calculated vehicle position with a location selected from a plurality of vehicle positions in a map database containing prestored positions obtained from an external system;

means for determining a plurality of correction factors, one for each sensed position and one for each calculated position; and

means for selecting one correction factor that, when used, makes a corrected vehicle position correspond to said selected location.

6. Apparatus for determining a location of a vehicle comprising:

means, responsive to a Global Positioning System, for determining a sensed position of said vehicle;

means, responsive to dead reckoning sensors, for determining a calculated position of said vehicle;

first comparison means for comparing said calculated position with a map database containing pre-stored locations obtained from an external system and for choosing therefrom a map-matched position of said vehicle;

second comparison means for comparing said calculated position and said sensed position with said chosen map-matched position and for producing a plurality of correction factors, one for each calculated position and one for each sensed position;

means for averaging said plurality of correction factors to produce a smoothed correction factor effective to produce a zero difference between said map-matched position and said sensed position; and

means for using said smoothed correction factor to correct said sensed position.

7. A hybrid vehicle navigation system comprising:

means for determining a sensed position of said vehicle from a Global Positioning System;

means for determining a calculated position of said vehicle by means of a dead reckoning sensor system;

a first comparison means for comparing said calculated position with a map database containing pre-stored locations obtained from an external system and for choosing therefrom a map-matched position of said vehicle;

a second comparison means for comparing said calculated position and said sensed position with said chosen map-matched position and for producing a plurality of correction factors for each of said calculated position and said sensed position;

means for averaging said plurality to produce a smoothed correction factor effective for producing a zero difference between said chosen map-matched position and said sensed position; and

means for correcting said vehicle position based on said smoothed correction factor.