Method and system for proximity detection and location determination

A method for determining the location of a railway vehicle along a track in a track layout having plural parallel tracks for at least a portion thereof and having switches between some of said parallel tracks, said railway vehicle comprising a satellite positioning system, a gyro, a linear position estimating device and a track database, comprising the steps of:

• (a) providing an approximate location of the vehicle from the satellite positioning system;
• (b) determining from the track database all track paths within a specified area of uncertainty from said approximate location;
• (c) establishing a Kalman filter for each determined track path, each of said filters monitoring the difference between the vehicle's heading as measured by said gyro and heading data stored in the track database;
• (d) monitoring at each Kalman filter as the vehicle moves along the track for residual differences in the heading state;
• (e) upon a residual difference exceeding a specified threshold value, eliminating the associated track path as one of the track paths;
• and,
• (f) upon the reduction of the number of track paths to one, declaring the associate path to be the path along which the vehicle is travelling.

A proximity detection system for a vehicle having an identification associated therewith and travelling along a predetermined track layout comprising:

• (a) a satellite positioning system which provides signals indicating the geographic location of the railway vehicle;
• (b) a track database which includes data regarding the track used by the railway vehicle, said track including plural track segments, and said data including the geographic position of track segments and the heading of track segments;
• (c) tachometer measuring the revolutions of one or more of the wheels of the vehicle for providing the position of the vehicle along the track;
• (d) a gyro for providing the change in heading of the vehicle;
• and,
• (e) filter which receives the signals indicating the geographic location, the position of the vehicle along the track, the heading of the vehicle and the track database to provide an estimate of the error in said geographic position the error in said heading and the error in said position of the vehicle along the track to determine the track position of the vehicle;
• (f) means for transmitting via a wireless link said identification and said track position;
• (g) means for receiving wireless signals from other vehicles, said wireless signals including the identifications and track positions of said other vehicles;
• (h) means for determining the distance along said track layout between said vehicle and said other vehicles;
• and
• (i) means for initiating an alarm if the determined distance is less than a predetermined amount.

A railway vehicle location determination system comprising:

• (a) a satellite positioning system which provides signals indicating the geographic location of the railway vehicle;
• (b) a track database which includes data regarding a track layout used by the railway vehicle, said track layout including plural track segments each having an associated mileage point, and said data including a geographic box associated with each mileage point;
• (c) a computer which compares the geographic location of the railway vehicle with said geographic boxes to select the geographic box in which the geographic location of the vehicle is located;
• and
• (d) a display for displaying the mileage point associated with the selected geographic box.

A railway vehicle location determination system comprising:

• (a) a satellite positioning system which provides signals indicating the approximate geographic location of the railway vehicle;
• (b) a track database which includes data regarding the track used by the railway vehicle, said track including all track paths within a specified region of uncertainty for said approximate position, and said data including the geographic position of track segments and the heading of track segments;
• (c) a tachometer measuring the revolutions of one or more of the wheels of the vehicle for providing the position of the vehicle along the track;
• (d) a gyro for providing the change in heading of the vehicle;
• (e) a Kalman filter for each track path within the specified region of uncertainty which receives the signals indicating the geographic location, the position of the vehicle along the track, the heading of the vehicle and the track database to provide an estimate of the error in said geographic position, the error in said heading and the error in said position of the vehicle along the track;
• and
• (f) a turn out processor for comparing the turn rate and the heading from said gyro with the turn rate and heading from said track database to determine which of said track paths the vehicle is traveling.