Author: GPS World Staff

A new system developed by Universidad Carlos III de Madrid (UC3M) researchers uses sensors to improve the ability of GPS to determine a vehicle’s position compared to use of conventional GPS devices by up to 90 percent.

The prototype can guarantee the position of the vehicle to within 1 or 2 meters in urban settings, the researchers said.

The system can be installed in any vehicle for little cost and may eventually work on smartphones, the researchers said. Their findings are described in the report, “Context-Aided Sensor Fusion for Enhanced Urban Navigation.”

Sensor Fusion. The prototype system incorporates a conventional GPS signal with those of other sensors (accelerometers and gyroscopes) to reduce the margin of error in establishing a location. “We have managed to improve the determination of a vehicle’s position in critical cases by between 50 and 90 percent, depending on the degree of the signals’ degradation and the time that is affecting the degradation on the GPS receiver,” said David Martín, a researcher at the Systems Intelligence Laboratory (LSI – Laboratorio de Sistemas Inteligentes) at UC3M. The system was jointly designed and developed by LSI and the Applied Artificial Intelligence Group (GIAA – Grupo de Inteligencia Aplicada Artificial).

The margin of error of a commercial GPS, such as those that are used in cars, is about 15 meters in an open field, where the receiver has wide visibility from the satellites. However, in an urban setting, the determination of a vehicle’s position can be off by more than 50 meters, due to the signals bouncing off of obstacles like buildings, trees, or narrow streets. In certain cases, such as in tunnels, communication is lost, hindering the GPS applications reaching Intelligent Transport Systems, which require a high level of security.

“Future applications that will benefit from the technology that we are currently working on will include cooperative driving, automatic maneuvers for the safety of pedestrians, autonomous vehicles or cooperative collision warning systems,” the scientists comment.

The greatest problem presented by a commercial GPS in an urban setting is the loss of all satellite signals. “This occurs continually, but commercial receivers partially solve the problem by making use of the urban maps that attempt to position the vehicle in an approximate point,” Martín said. “These devices can indicate to the driver approximately where he is, but they cannot be used as a source of information in an Intelligent Transport System like those we have cited.”

The basic elements that make up this system are a GPS and a low-cost inertial measurement unit (IMU). The latter device integrates three accelerometers and three gyroscopes to measure changes in velocity and maneuvers performed by the vehicle. Then, everything is connected to a computer that has an application that merges the data and corrects the errors in the geographic coordinates. Enrique Martí of UC3M’s GIAA explains, “This software is based on an architecture that uses context information and a powerful algorithm (an unscented Kalman filter) that eliminates the instantaneous deviations caused by the degradation of the signals received by the GPS receiver or the total or partial loss of the satellites.”

The current prototype can be installed in any type of vehicle. It is already working on board the IVVI (Intelligent Vehicle based on Visual Information, pictured above), a car that has become a platform for research and experimentation for professors and students at the university.

The LSI and UC3M researchers working on this “intelligent car” can capture and interpret all of the information available on the road, and that drivers use. To do this, the team is using optical cameras, infrareds and lasers to detect whether drivers are crossing the lines on the road, or whether there are pedestrians in the vehicle’s path, as well as to adapt the speed to the traffic signals and analyze the driver’s level of sleepiness in real time.

Next Steps. The researchers will analyze the possibility of developing a system that makes use of the sensors that are built into smartphones, because intelligent telephones are equipped with more than ten sensors, such as an accelerometer, a gyroscope, a magnetometer, GPS and cameras, in addition to Wi-Fi, Bluetooth or GSM communications.

“We are now starting to work on the integration of this data fusion system into a mobile telephone,” said Enrique Martí, “so that it can integrate all of the measurements that come from its sensors in order to obtain the same result that we have now, but at an even much lower cost, since it is something that almost everyone can carry around in his pocket.”