MEMS sensors have developed substantially over the last 15 years in many respects. A number of new approaches have been very successful and this has led to high performance devices. Advances in the micro-machining techniques have provided a substantial enhancement to the technology, leading to substantial cost reduction. As the technology has advanced there has been a greater understanding of the cause and effects of the error mechanisms and the need for a close integration between the sensing element and the electronic control circuits. The performance of MEMS devices has increased by many orders of magnitude over a decade or so, owing to successful development projects. Consequently, MEMS accelerometers and gyroscopes are capable of providing inertial-grade measurements of acceleration and angular motion for long-range navigation systems.