Time flies since the debut of this book. In the past ten years, localization technology has evolved from small saplings into towering trees. Robots and drones with autonomous positioning and navigation capabilities, once considered unreachable fantasies, have gradually become a reality. However, while we are being amazed at the groundbreaking changes brought about by technology, as researchers, we still need to remain acutely attentive to the current limitations of localization. Some signif ...