Combining multiple GPS receivers to enhance relative distance measurements

Inexpensive, commercial available off-the-shelf (COTS) Global Positioning Receivers (GPS) have typical accuracy of ±3 meters when augmented by the Wide Areas Augmentation System (WAAS). There exist applications that require position measurements between two moving targets. The focus of this work is to explore the viability of using clusters of COTS GPS receivers for relative position measurements to improve their accuracy. An experimental study was performed using two clusters, each with five GPS receivers, with a fixed distance of 4.5 m between the clusters. Although the relative position was fixed, the entire system of ten GPS receivers was on a mobile platform. An expensive RTK GPS system, accurate to the centimeter level, was also fixed to the mobile platform and used for comparison. Data was recorded while moving the system over a rectangular track with a perimeter distance of 7564 m. The cluster data was post processed and yielded approximately one meter accuracy for the relative position vector between the two clusters. Furthermore, the 2σ and RMS values were decreased by approximately 13 fold from a worst case scenario.