Basic Feasibility of GPS Positioning without Carrier-Phase Measurements as a Relative Position Sensor between Two Vehicles

C. Christopher Kellum

Abstract:	Recent progress in the field of vehicle-to-vehicle communications is likely to enable the exchange of position information between vehicles at a rate higher than once per second and up to ten times per second. Since GPS receivers coupled with vehicle-to-vehicle communication creates a new form of object detection sensor, this paper explores the feasibility and establishes an expectation baseline for use of estimated absolute positions from GPS receivers to determine the relative position between vehicles in order to support active safety and driver assistance systems. Two different test configurations are presented to explore the feasibility of this approach. The locations where the tests were performed were chosen to be favorable to GPS, implying they contained very few trees and overhead objects that might have obstructed the GPS antennas’ line of sight to GPS satellites. No vehicle information, such as yaw-rate or speed, was used to aid the receiver or the absolute position estimate produced by the GPS receivers. The first test configuration uses two GPS receivers mounted on the roof of one vehicle to determine whether a mobile environment adds significant relative position error when using estimated absolute position from the GPS receivers. The second test configuration uses three grades of GPS receiver mounted on two different vehicles to compare relative position measurement performance against that of a radar unit mounted at the front of the following vehicle. Analysis of the test data indicates that relative position measurement using estimated absolute positions from GPS receivers may work well for certain types of GPS receivers. As expected, the more capable GPS receiver resulted in better positioning. However, the performance difference between the low-end and mid-range GPS receivers chosen for this test was surprising. The results indicate that the low-end GPS receiver is unable to meet requirements to support more advanced active safety or driver assistance applications while the mid-range GPS receiver may. This research indicates that using estimated absolute positions from GPS receivers for measuring the relative position between two vehicles might meet accuracy requirements of many systems that require this information. Under the assumption that all relevant vehicles contain a vehicle-to-vehicle communication system, the vehicles may be able to exchange GPS receiver position estimates to determine the relative position between the vehicles without additional object detection sensors such as radar.
Published in:	Proceedings of the 2005 National Technical Meeting of The Institute of Navigation January 24 - 26, 2005 The Catamaran Resort Hotel San Diego, CA
Pages:	903 - 910
Cite this article:	Kellum, C. Christopher, "Basic Feasibility of GPS Positioning without Carrier-Phase Measurements as a Relative Position Sensor between Two Vehicles," Proceedings of the 2005 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2005, pp. 903-910.
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