I. Introduction
Localization and mapping [1] play key roles in various applications, such as, unmanned aerial vehicles [2], unmanned ground vehicles [3], autonomous cars [4], service robots [5], virtual and augmented reality. These technologies are essential components of autonomous robots. They allow a robot to build a map of the environment and to track its relative position within the map. Using the map and the pose information, the robot can perform path planning, navigation, obstacle avoidance, etc.