News Column

Patent Issued for Navigation System Using Both GPS and Laser Reference

May 7, 2014

By a News Reporter-Staff News Editor at Journal of Engineering -- From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventors Taylor, Arthur (Boulder, CO); Talbot, Nicholas C. (Ashburton, AU), filed on October 17, 2006, was published online on April 22, 2014.

The patent's assignee for patent number 8705022 is Trimble Navigation Limited (Sunnyvale, CA).

News editors obtained the following quote from the background information supplied by the inventors: "The current invention relates to position tracking and machine control systems and, in particular, to a combination of a laser system and a global navigation satellite system to track the position of a machine and to provide accurate control of the machine based on the tracking information.

"Global navigation satellite systems (hereinafter collectively referred to as GNSS), like GPS, and GLONASS, have been used extensively to determine position coordinates. Such position coordinates can be used in surveying operations, and for automated control of mobile units. In the future, the European GALILEO system will have similar capabilities. An autonomous navigational system that includes a satellite receiver and a navigational computer can achieve a 10-meter level of accuracy in determining the position of a mobile unit using solely the satellite signals. Differential navigational systems that utilize differential corrections in addition to the satellite signals can determine the positional information to within a meter range of accuracy. Real-time kinematic (RTK) navigational systems that are capable of utilizing both code and carrier information transmitted from such satellites can achieve centimeter level accuracy.

"While such GNSS systems are capable of monitoring the movement of mobile equipment and operating as a part of a system that controls the operation of such equipment, such as for example graders and other types of earthmoving equipment, global navigation satellite systems cannot operate effectively when satellites are blocked or partially blocked from view. Optimally, such global navigation satellite systems receive data from all satellites in view and calculate the position of the receiver based all satellites. Such systems are capable of operating when receiving transmissions from only four satellites, or when satellite geometry is weak (the geometric dilution of precision is high), however system positioning accuracy and performance will degrade. It is clear that when fewer than four satellites are being received, or when more than four satellites are tracked but the satellite geometry is weak, the control of the system must be achieved in an alternative manner. Further, in some instances, even when transmissions from five satellites are received, the accuracy achievable is less than desired."

As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventors' summary information for this patent: "To deal with those instances when signals from satellites are being obstructed, or when satellite positions prevent accurate position determination, a laser based positioning system can be arranged to provide supplemental information as to machine position. For example, if a motorgrader is about to travel under an overpass, it can be anticipated that the motorgrader system will lose sight of a number of the satellites. Since global navigation satellite systems operate with the receiver receiving on a line-of-sight basis, it should be anticipated that there will be a significant loss of satellite reception. To compensate for such loss, and for the loss of position data, a supplemental position information source, such as a stationary laser transmitter, cooperates with a laser receiver on the machine to determine machine position. The stationary laser transmitter effectively takes the place of a blocked satellite, allowing the control of the motorgrader to continue, unaffected, as the machine moves under the overpass and back into a position where it has a clear view of all of the satellites.

"Since the position of the machine is determined in part with regard to the laser transmitter, it is important for the positioning system to determine the position of the laser transmitter in the same coordinate system as that in which the positioning system operates when under global navigation satellite system control. While it is possible to determine in advance the position of the laser transmitter using manual surveying techniques, it will be appreciated that this may slow down the operation of the positioning system and present opportunities for errors to be made, as well.

"The present invention contemplates a combination laser system and global navigation satellite positioning system that allows a user to realize high precision control of mobile units, including high precision machine control, without necessitating an extensive set up procedure. The positioning system comprises a laser transmitter, an optical sensor, a GPS receiver, and a device receiving and utilizing the signals from the optical sensor and the GPS receiver. The laser transmitter projects at least one laser beam that rotates about a generally vertical axis. The GPS receiver, including a GPS antenna, determines the position of the antenna. The optical sensor may be coaxial with, or displaced a small distance from, the phase center of the GPS antenna. Alternatively the optical sensor may be simply positioned a fixed position with respect to the phase center of the GPS antenna. The optical sensor receives the laser beam. The device receives signals from the GPS receiver and signals from the optical sensor to determine the position of the transmitter. Thereafter, the device utilizes signals received from the optical sensor to improve the estimate of position based on the signals from the GPS receiver. This positioning system may determine the position of a machine and then be used for controlling the machine by providing a control signal. The GPS data and the optical sensor data may advantageously be combined in a Kalman filter.

"Accordingly, it is an object of the present invention to provide a system for determining the position of a machine and controlling the machine in which the operation of the system is facilitated."

For additional information on this patent, see: Taylor, Arthur; Talbot, Nicholas C.. Navigation System Using Both GPS and Laser Reference. U.S. Patent Number 8705022, filed October 17, 2006, and published online on April 22, 2014. Patent URL:

Keywords for this news article include: Trimble Navigation Limited.

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Source: Journal of Engineering

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