This comprehensive volume presents the theory and implementation of strap‑down inertial navigation systems, a class of devices that compute orientation and position by directly mounting accelerometers and gyroscopes to a moving platform. Covering sensor modeling, error analysis, and algorithmic integration techniques, the text guides readers through the mathematical foundations and practical considerations essential for aerospace and automotive applications. Detailed examples illustrate how strap‑down architectures simplify hardware while demanding sophisticated software processing, making the work a valuable reference for engineers, researchers, and advanced students in the field of navigation and control systems.