This book presents the current research on space-based navigation models and the contents of spaces used for seamless indoor and outdoor navigation. It elaborates on 3D spaces reconstructed automatically and how indoor, semi-indoor, semi-outdoor, and outdoor spaces can mimic the indoor environments and originate a network based on the 3D connectivity of spaces. Case studies help readers understand theories, approaches, and models, including data preparation, space classification and reconstruction, space selection, unified space-based navigation model derivation, path planning, and comparison of results. Features: Provides novel models, theories, and approaches for seamless indoor and outdoor navigation path planning Includes real-life case studies demonstrating the most feasible approaches today Presents a generic space definition framework that can be used in research areas for spaces shaped by built structures Develops a unified 3D space-based navigation model that allows the inclusion of all types of spaces as 3D spaces and utilizes them for seamless navigation in a unified way Intended to motivate further research and developments, this book suits students, researchers, and practitioners in the field, and serves as a helpful introductory text for readers wanting to engage in seamless indoor/outdoor navigation research and teaching.