An Improved Method for GPS-Based Network Position Location in Forests

In this paper we present a technique for improving the location performance based on the Global Positioning System (GPS) for networks of nodes in harsh environments and demonstrate its efficacy via a combination of simulations and measurements in forests. The technique relies on the use of Ultra-wideband (UWB) signals to measure time-of-flight (TOF) and consequently the range between nodes to improve localization in harsh forest environments. Specifically, we create a system of range equations based on network connectivity and solve this system of non-linear equations using a Least-Squares Non-Linear optimization technique using any available GPS information as the initial estimate. Based on our simulations and measurements, the improved technique results in a localization accuracy in forests that is on par with clear-field reference GPS measurements.