1. A system, comprising: an image acquisition device configured to acquire an image via scanning an image frame over a period of time; an inertial measurement unit configured to measure at least one of a position, an orientation, and a movement of the image acquisition device during the period of time and output an indication of the movement as detected; and a state estimation module, operatively coupled to the inertial measurement unit and the image acquisition device, configured to estimate a state related to at least one of position and orientation of the image acquisition device based on the at least one of the position, the orientation, and the movement, wherein the state estimation module is configured to use a parametric model of the errors in the state estimates to effect the computation of the state updates, and to vary a number of terms in the parametric model of the errors in response to a magnitude of one or more errors.