BACKGROUND

Technical Field

The subject matter described herein relates to control of single or multi-vehicle systems based on determining positions of the vehicle systems.

Discussion of Art

In connection with the control one or more operations of a train, sometimes called “positive train control” (PTC), it can be desirable to be able to dynamically ascertain the position of the train as it travels along a track. Presently, global positioning systems (GPS) can be used to dynamically determine positions of a train and dead reckoning techniques may be used when GPS is not available.

When GPS is used, a lead vehicle of the train can include a first GPS receiver coupled to or part of a head of train (HOT) unit used for train control, and the last vehicle of the train can include a second GPS receiver coupled to or as part of an end of train (EOT) unit. In response to receiving a sample of GPS satellite data, the first GPS receiver can determine and output a first geographical location of the lead vehicle of the train and the first GPS receiver. In response to receiving the same or a different sample of GPS satellite data, the second GPS receiver can determine and output a second geographical location of the last vehicle of the train and the second GPS receiver.

The rate that each of the first and second GPS receivers sample GPS satellite data (e.g., between 1 Hz and 10 Hz) can be sufficiently fast that variances in the time each GPS receiver samples GPS satellite data can have little or no effect on the ability of the GPS receiver to dynamically determine the geographical location of the receiver when the GPS satellite data was sampled, or the determination and use of the first and second geographical locations of the lead and last vehicles determined from said samples in connection with train control. Each GPS receiver can sample GPS satellite data periodically and/or aperiodically as deemed suitable and/or desirable.

Upon the second GPS receiver determining a second geographical location of the last vehicle of the train based on the sampled GPS satellite data, the EOT can communicate this second geographical location to the HOT via a communication link (e.g., a wireless communication link) between the HOT and EOT. Because the HOT is now aware of the second geographical location communicated to the HOT by the EOT, and is aware of the first geographical location of the lead vehicle from the output of the first GPS receiver based on GPS satellite data sampled thereby, the HOT can control one or more operations of the train based on these first and second geographical locations.

The process of the first and second GPS receivers sampling GPS satellite data and determining the first and second geographical locations of the lead and last vehicles of the train can be repeated (e.g., continuously) as long as desired as an aid to the safe operation of the train.

First and second geographical locations of the lead and last vehicles of train based on GPS satellite data can have an accuracy of ≤7.8 meters with a 95% probability (see e.g., https://www.gps.gov/systems/gps/performance/accuracy/). However, it would be desirable to improve this accuracy, e.g., within 1-4 centimeters, without the introduction of additional, possibly expensive and power hungry, hardware (e.g., receiver).

BRIEF DESCRIPTION

In one embodiment, a system includes a first communication unit including a first receiver configured to be disposed onboard a vehicle system. The first receiver is configured to receive satellite positioning data and to receive position correction data that is based on phase measurements of satellite signals. The system also includes a second communication unit including a second receiver configured to be disposed onboard the vehicle system in a different location than the first receiver, the second receiver configured to receive the satellite positioning data. The system also includes one or more processors configured to determine first geographical position data corresponding to a first geographical position of the first receiver based on the position correction data and the satellite positioning data received by the first receiver. The one or more processors are configured to communicate the position correction data or a copy of the position correction data to the second communication unit. The one or more processors are configured to determine second geographical position data corresponding to a second geographical position of the second receiver based on the position correction data received at the second communication unit and the satellite positioning data received by the second receiver. The one or more processors are configured to communicate the second geographical position data that is determined to the first communication unit.

In another embodiment, a method includes receiving satellite positioning data at a first communication unit onboard a vehicle system, receiving position correction data that is based on phase measurements of satellite signals at the first communication unit, receiving the satellite positioning data at a second communication unit onboard the vehicle system, determining first geographical position data corresponding to a first geographical position of the first communication unit based on the position correction data and the satellite positioning data received by the first communication unit, receiving the position correction data or a copy of the position correction data at the second communication unit, determining second geographical position data corresponding to a second geographical position of the second communication unit based on the position correction data received at the second communication unit and the satellite positioning data received by the second communication unit, and communicating the second geographical position data that is determined to the first communication unit.

In one embodiment, a system includes a first communication unit configured to be disposed onboard a vehicle system at a first location. The first communication unit is configured to receive satellite positioning data and position correction data that is based on phase measurements of satellite signals from an off-board station. The first communication unit is configured to determine a first geographical position of the first communication unit based on the position correction data and the satellite positioning data. The system also includes a second communication unit configured to be disposed onboard the vehicle system at a second location that is different from the first location. The second communication unit is configured to receive the satellite positioning data and the position correction data. The second communication unit is configured to determine a second geographical position of the second communication unit based on the position correction data and the satellite positioning data. The second communication unit is configured to communicate the second geographical position to the first communication unit for use in controlling an operation of the vehicle system.

