GPS/INS integration with fault detection and exclusion in shadowed environments

This paper presents a method for GPS/INS operation in shadowed environments such as urban canyons and rural foliage cover. Shadowing causes a combination of multipath and signal attenuation which results in increased uncertainty in the GPS observables and sometimes complete loss of satellite tracking. Environment layout and the line-of-sight vector to the affected satellite determines the degree of shadowing in the range domain. Details are provided for the failure modes and effects in such environments. These results are used in the analysis of a fault detection and exclusion (FDE) algorithm to provide integrity to the GPS observables.