A New Multilateration System for Ground Surveillance

In the vicinity of buildings and aircraft in airports, conventional multilateration systems sometimes have difficulties in positioning precisely due to reflected signals, so-called multipath. To overcome this problem, ENRI has invented a new multilateration system for ground surveillance, named as Optically ConnecTed PAssive Surveillance System (OCTPASS). OCTPASS uses the same techniques as conventional multilateration systems. For instance, OCTPASS computes target’s positions with Time Differences Of Arrival (TDOA) between ground stations. The major difference from conventional systems is that OCTPASS ground stations directly transmit RF signals to the main processor through Radio On Fiber (ROF) devices and optical fiber cables. This feature enables OCTPASS to position targets with high accuracy under multipath environments. In 2004, to evaluate the performance of OCTPASS, we developed a test system for 1090MHz Mode S signal and conducted tests in an airport. In this paper, we first introduce the test system. Then we show the results of tests. The results show that OCTPASS is capable of positioning targets with high accuracy under multipath environments.