GPS tracking down to the centimeter
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Researchers at the University of Califogrnia, Riverside have
developed a new, more computationally efficient way to
process data from the Global Positioning System (GPS), to
enhance location accuracy from the meter-level down to a
few centimeters.
The optimization will be used in the development of
autonomous vehicles, improved aviation and naval navigation
systems, and precision technologies. It will also enable users
to access centimeter-level accuracy location data through
their mobile phones and wearable technologies, without
increasing the demand for processing power.
The research, led by Jay Farrell, professor and chair of
electrical and computer engineering in UCR's Bourns College
of Engineering, was published recently in IEEE's
Transactions on Control Systems Technology. The approach
involves reformulating a series of equations that are used
to determine a GPS receiver's position, resulting in reduced
computational effort being required to attain centimeter
accuracy.
First conceptualized in the early 1960s, GPS is a space-
based navigation system that allows a receiver to compute
its location and velocity by measuring the time it takes to
receive radio signals from four or more overhead satellites.
Due to various error sources, standard GPS yields position
measurements accurate to approximately 10 meters.
Differential GPS (DGPS), which enhances the system
through a network of fixed, ground-based reference
stations, has improved accuracy to about one meter. But
meter-level accuracy isn't sufficient to support emerging
technologies like autonomous vehicles, precision farming, and
related applications.
"To fulfill both the automation and safety needs of
driverless cars, some applications need to know not only
which lane a car is in, but also where it is in that lane--
and need to know it continuously at high rates and high
bandwidth for the duration of the trip," said Farrell, whose
research focuses on developing advanced navigation and
control methods for autonomous vehicles.
Farrell said these requirements can be achieved by
combining GPS measurements with data from an inertial
measurement unit (IMU) through an internal navigation
system (INS). In the combined system, the GPS provides
data to achieve high accuracy, while the IMU provides data
to achieve high sample rates and high bandwidth
continuously.
Achieving centimeter accuracy requires "GPS carrier phase
integer ambiguity resolution." Until now, combining GPS and
IMU data to solve for the integers has been computationally
expensive, limiting its use in real-world applications. The UCR
team has changed that, developing a new approach that
results in highly accurate positioning information with
several orders of magnitude fewer computations.
"Achieving this level of accuracy with computational loads
that are suitable for real-time applications on low-power
processors will not only advance the capabilities of highly
specialized navigation systems, like those used in driverless
cars and precision agriculture, but it will also improve
location services accessed through mobile phones and other
personal devices, without increasing their cost," Farrell said.
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