Method for correcting position error in navigation system

• US 20040044477A1
• Filed: 09/02/2003
• Published: 03/04/2004
• Est. Priority Date: 09/02/2002
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Jung, Mun Ho, Joe, Moon Jeung
• Granted Patent: US 6,931,322 B2
• Time in Patent Office: Days
• US Class Current: 702/5
• CPC Class Codes: G01C 21/30 Map- or contour-matching
• CPC Class Codes: G01S 19/49 whereby the further system is an inertial position system, e.g. loosely-coupled
• CPC Class Codes: G01S 19/50 whereby the position solution is constrained to lie upon a particular curve or surface, e.g. for locomotives on railway tracks

Abstract

A method for correcting position error in a navigation system enables one to more accurately match a position measurement of a moving object on a digital map. Particularly, the method comprises the steps of: receiving a current position measurement of a moving object from GPS/DR (Dead Reckoning)—based information; correcting the current location measurement using a displacement-corrected value; performing map matching using the corrected current position measurement; calculating variation of correction angle by extracting a current correction angle out of the map matching result; converting and correcting a previous displacement-corrected value to the current correction angle; and compensating the displacement-corrected value by applying a predetermined constant to the converted displacement-corrected value, and storing the compensated displacement-corrected value.

Claims

1. A method for correcting position error in a navigation system, the method comprising the steps of:

receiving a current position measurement of a moving object from GPS/DR (Dead Reckoning)—

based information;

correcting the current location measurement using a displacement-corrected value;

performing map matching using the corrected current position measurement;

calculating variation of correction angle by extracting a current correction angle out of the map matching result;

converting and correcting a previous displacement-corrected value to the current correction angle; and

compensating the displacement-corrected value by applying a predetermined constant to the converted displacement-corrected value, and storing the compensated displacement-corrected value.

2. The method according to claim 1, wherein the variation of correction angle is a difference between a current correction angle being calculated and a previously map-matched correction angle, the current correction angle being calculated based on the map-matched position of the moving object and a link angle.

3. The method according to claim 1, wherein the current correction angle is calculated from a formula, a tan 2 {(MMx−

GPSx), (MMy−

GPSy)}, wherein GPSx and GPSy denote X-axis and Y-axis measurements of the current position of the moving object; and

MMx and MMy are map-matched X-axis and Y-axis position measurements obtained by matching GPSx and GPSy with the map.

4. The method according to claim 1, wherein the displacement-corrected values are obtained in X-axis and Y-axis, respectively.

5. The method according to claim 1, wherein the displacement-corrected values are obtained by Equations below:

x-displacement corrected value=(MMx−

GPSx)+d * sin (link angle+90°

)y-displacement corrected value=(MMy−

GPSy)+d * cos (link angle+90°

)

wherein, GPSx and GPSy are current location measurements of the moving object in X-axis and Y-axis;

MMx and MMy are map-matched X-axis and Y-axis position measurements obtained by matching GPSx and GPSy with the map; and

d is an absolute correction distance, which is a straight distance between the current location measurement and the map-matched link position.

6. The method according to claim 1, wherein a compensation coefficient of the displacement-corrected value indicates a directional compensation value along heading of the moving object, being +1 or −

1.

7. The method according to claim 1, wherein a sign of a compensation coefficient of the displacement-corrected value changes if a variation angle between the correction angle and the previous correction angle is less than a predetermined level, and if GPS and DR value changes from the left side the right on a link.

8. The method according to claim 1, wherein a sign of a compensation coefficient of the displacement-corrected value changes if a variation angle between a link angle and the correction angle is in a predetermined range, and the corrected GPS value is located at the right side of a link.

9. The method according to claim 1, wherein compensated displacement-corrected values to which the compensation coefficient is respectively added are represented by Equations below:

x-displacement corrected value=(MMx−

GPSx)+K * d * sin (link angle=90°

)y-displacement corrected value=(MMy−

GPSy)+K * d * cos (link angle=90°

).

10. The method according to claim 5, wherein the absolute correction distance (d) is a straight distance between a GPS/DR—

based location measurement and a map-matched location measurement.

11. The method according to claim 5, wherein the absolute correction distance (d) is obtained from Equation of d={square root}{square root over ((x1,x2)²+(y1,y2)²)}, wherein x1 denotes a previously map matched x-displacement corrected value;

y1 denotes a previously map matched y-displacement corrected value;

x2 denotes a converted x-displacement corrected value of previous map matching using a current correction angle; and

y2 denotes a converted y-displacement corrected value of previous map matching using a current correction angle

12. The method according to claim 11, wherein the converted x-displacement corrected value (x2) of previous map matching using the current correction angle is obtained by x2=d * sin (θ

2), and the converted y-displacement corrected value (y2) of previous map matching using the current correction angle is obtained by y2=d * cos (θ

2), in which θ

2 indicates an angle between a new GPS/DR position measurement and a map-matched value plotted on a Cartesian coordinate system using the direction of true north as a reference line.

13. A method for correcting position error in a navigation system, the method comprising the steps of:

receiving a current position measurement of a moving object by making use of a GPS/DR (Dead Reckoning) method;

correcting the current location measurement using a previous displacement-corrected value;

performing map matching using the corrected current position measurement; and

calculating out of the map matching result a variation of correction angle, and a compensated displacement-corrected value along heading by extracting a current correction angle out of the map matching result.

14. The method according to claim 13, further comprising the steps of:

after map matching is performed, calculating a variation angle by extracting correction angle out of the map matching result;

converting and correcting a previous displacement-corrected value to the current correction angle; and

calculating a displaced-corrected value by compensating the displacement-corrected value applying to the converted displacement-corrected value a predetermined constant opposite to a correction direction, and storing the compensated displacement-corrected value.

15. A method for correcting position error in a navigation system, the method comprising the steps of:

receiving a current position measurement of a vehicle obtained from a GPS signal and sensors installed in the vehicle;

correcting the current position measurement of the vehicle to a previously map-matched x- and y-displacement corrected values, and performing map matching on the corrected values;

calculating a current correction angle by extracting a map-matched position of the vehicle and a link angle;

calculating variation of correction angle between the current correction angle and a previously map-matched correction angle, and deciding whether the variation of correction angle is less than a predetermined angle;

if the variation of correction angle is not less than the predetermined angle, initializing x- and y-displacement corrected values to ‘

0’

; and

storing x- and y-displacement corrected values being calculated.

16. A method for correcting position error in a navigation system, the method comprising the steps of:

receiving a GPS position measurement;

extracting candidate links within a predetermined search range around the GPS position measurement;

among a plurality of interpolation points on the candidate links, selecting a spot between interpolation points with highest possibilities; and

among candidate links including the selected spot between interpolation points, selecting a link with a highest possibility of having a moving object, and performing map matching.