An apparatus for providing three-dimensional pose comprising monocular visual sensors for providing images of an environment surrounding the apparatus, an inertial measurement unit (IMU) for providing gyroscope, acceleration and velocity information, collectively IMU information, a feature tracking module for generating feature tracking information for the images, and an error-state filter, coupled to the feature track module, the IMU and the one or more visual sensors, for correcting IMU information and producing a pose estimation based on at least one error-state model chosen according to the sensed images, the IMU information and the feature tracking information.