  Inertial navigation and attitude initialization in polar areas become a hot
topic in recent years in the navigation community, as the widely-used
navigation mechanization of the local level frame encounters the inherent
singularity when the latitude approaches 90 degrees. Great endeavors have been
devoted to devising novel navigation mechanizations such as the grid or
transversal frames. This paper highlights the fact that the common Earth-frame
mechanization is sufficiently good to well handle the singularity problem in
polar areas. Simulation results are reported to demonstrate the singularity
problem and the effectiveness of the Earth-frame mechanization.
