NLOS Mitigation Methods for Geolocation

It is well known that the presence of non-line-of-sight (NLOS) errors in the geolocation problem leads to severe degradation in the localization performance. Assuming that redundant location metrics measurements are available and the number of line-of-sight (LOS) measurements available satisfies the minimum requirement to compute the location estimates, the NLOS errors can then be identified or its effect can be mitigated. This chapter introduces NLOS mitigation methods for geolocation. Generally, the NLOS mitigation methods for geolocation can be grouped into four categories. They are the methods based on maximum likelihood (ML), least squares (LS), and constrained optimization, as well as robust statistics. These methods are compared in terms of different performance measures. The chapter also discusses a novel geolocation example using a single moving sensor. Numerical examples are presented to demonstrate how position estimation can be achieved for the case of a single moving sensor with NLOS errors.