Unmanned Aerial Vehicles (UAVs) represent a high potential for many fields of applications, from surveying to search and rescue missions, from delivery to photography. For all these applications, the interest in this field become higher for those that require automatic missions and autonomous flight operations. In order to consider autonomous flights, one of the most essential requirements is the capability of detect obstacles and avoid them through reliable mechanisms. Nowadays, obstacle avoidance is an incredibly active field of research and development, considering that several aspects of this area are still unknown. For example, obstacle avoidance in three dimensions is less developed than two-dimensional methods, but represents a cardinal point for all types of systems that can move in three-dimensional space.