1. A navigation device, comprising: a monocular camera configured to capture image frames at discrete time intervals; an inertial measurement unit configured to measure angular rate and acceleration; and a processor coupled to the monocular camera and the inertial measurement unit, wherein the processor is configured to execute software, wherein the software comprises a feature extraction and data association functionality and a filter functionality that: tracks one or more features from a first image frame captured at a first location and from a second image frame captured at a second location; determines a physical displacement of the navigation device based on the measured angular rate and acceleration; determines a position correction based on the relative movement of the one or more features between the first image frame and the second image frame wherein the processor determines the position correction by calculating a set of 3D coordinates of the one or more features and stores the set of 3D coordinates in a landmark database, wherein the filter functionality comprises a hybrid extended Kalman filter having state vectors including position, velocity, and attitude, representations of tracked features in the landmark database, and a focal length f of the at least one monocular camera; and outputs navigation data based on the physical displacement and the position correction; and wherein feedback from the navigation data is used for tracking the one or more features.