# US 7,610,152 B2 · Train navigator with integral constrained GPS solution and track database compensation

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- Number: US 7,610,152 B2
- Document ID: US7610152B2
- Status: Granted
- Kind: B2
- Application number: 11/416,069
- Filed: 2006-05-03
- Published: 2006-11-30
- Granted: 2009-10-27
- Earliest claimed: 2005-05-04
- Assignees: Lockheed Martin Corporation
- Inventors: Thomas J. Meyer
- Web page: https://patentgrep.com/patent/US7610152B2

## CPC

- B61L 25/025: {Absolute localisation, e.g. providing geodetic coordinates}
- B61L 2205/04: Satellite based navigation systems, e.g. global positioning system [GPS]
- B61L: GUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC (brakes or auxiliary equipment B61H, B61K; point or crossing construction E01B)

## Abstract

The present invention provides a new set of algorithmic solutions to accommodate track inaccuracy information in track databases. Navigation and measurement aiding processes are defined by a stochastic mode relative to a moving rail frame defined so that it is aligned with the heading of the compensated track database at the current along track-position. Filtering generates long and short wavelength track alignment disturbances commensurate with track grade to compensate for track database errors; a stochastic error model is defined as the difference between the deterministic implementation and the actual stochastic processes Bayesian estimation of the error variables is implemented via a digital Kalman filter with the navigation, database, and measurement errors removed by subtracting the filter estimates.

## Claims

### Claim 1

A method for navigation in a system including railway track having a plurality of track irregularity classes with a quantitative value associated with each class and a railway vehicle for movement along the railway track having a navigation system for determining railway vehicle position along the railway track, the navigation system including a database having at least a geometric track model contained therein, the navigation system also including inertial components for measuring heading and variations thereof and acceleration and variations thereof and a satellite responsive GPS for providing geopositional data, comprising the steps of:
establishing an a-priori stochastic model of actual navigation errors and an a-priori stochastic model of a measurement aiding process;
effecting a Kalman type filtering of error variables to create estimated track database errors constrained by the track irregularity class; and
implementing substantially real-time feedback of estimated track database errors for correcting the geometric track model contained in the database for subsequent use for navigation upon the railway track.

### Claim 2 (depends on 1)

The method of claim 1, wherein said second-mentioned step includes providing, as an input thereto, a satellite-based GPS measurement related to a current position of the railway vehicle on the railway track.

### Claim 3

A method for rail track database compensation in a system including railway track having a plurality of track irregularity classes with a quantitative value associated with each class and a railway vehicle for movement along the railway track having a navigation system for determining railway vehicle position along the railway track, the navigation system including a database having at least a geometric track model contained therein, the navigation system also including inertial components for measuring heading and variations thereof and acceleration and variations thereof and a satellite responsive GPS for providing geo-positional data, comprising the steps of:
establishing an a-priori stochastic model of actual navigation errors and an a-priori stochastic model of a measurement aiding process;
effecting a Kalman type filtering of error variables to create estimated track database errors constrained by the track irregularity class; and
implementing substantially real-time feedback of estimated track database errors for correcting the geometric track model contained in the database for subsequent use for navigation upon the railway track.

### Claim 4 (depends on 3)

The method of claim 3, wherein said second-mentioned step includes providing, as an input thereto, a satellite-based GPS measurement related to a current position of the railway vehicle on the railway track.

### Claim 5

A method of simultaneous navigation and rail track database correction in a system including railway track having a plurality of track irregularity classes with a quantitative value associated with each class and a railway vehicle for movement along the railway track having a navigation system for determining railway vehicle position along the railway track, the navigation system including a rail track database having at least a geometric track model contained therein, the navigation system also including inertial components for measuring heading and variations thereof and acceleration and variations thereof and a satellite responsive GPS for providing geo-positional data, comprising the steps of:
establishing an a-priori stochastic model of actual navigation errors and an a-priori stochastic model of a measurement aiding process;
effecting a Kalman type filtering of error variables to create estimated track database errors constrained by the track irregularity class; and
implementing substantially real-time feedback of estimated track database errors previously presented for navigation upon the railway track.

### Claim 6 (depends on 5)

The method of claim 5, wherein said second-mentioned step includes providing, as an input thereto, a satellite-based GPS measurement related to a current position of the railway vehicle on the railway track.