Optimization of a GPS-Based Navigation Reference System

摘要

The development of increasingly accurate new aircraft navigation systems hascaused the Air Force to develop a new Navigation Reference System to test them, called the Submeter Accuracy Reference System (SARS). The SARS is an inverted GPS system which consists of an array of GPS receivers on the ground and an airborne pseudolite mounted on the test aircraft. The SARS will provide a proof position estimate that is used to check the navigation system under test. Unfortunately, ground based inverted GPS systems tend to suffer from high geometric sensitivity to measurement errors. This research tackles the problem of optimizing the SARS receiver array configuration to minimize the system's sensitivity to pseudorange errors. The analysis determines that the proper choice of cost function for the optimization is the condition number of the H matrix, rather than the commonly used GDOP. Insight into the problem is provided by a graphical technique for evaluating receiver array geometry. Moreover, two receiver array numerical optimization programs are developed. The results of the receiver array optimization show that the geometric sensitivity to error in the SARS airspace can be reduced to acceptable levels through proper array design. Several good receiver array designs are shown. Finally, a technique for further reducing the geometric sensitivity of the SARS is discussed.