Dr. John G. Mark is a recognized international authority on inertial and multi-sensor navigation and a pioneer in the field of strapdown inertial systems. During his career at Litton, Dr. Mark has been at the forefront of navigation technology and holds over 50 patents and is the inventor of most strapdown algorithms used in Litton navigation systems. Beginning in 1973, Dr. Mark developed the first Litton strapdown navigation algorithms using highly efficient real-time implementations and demonstrated 1nmi/hr flight performance in 1975 using tuned rotor gyros. At that time, he successfully developed fast fixed point algorithms that match and in some cases exceed the performance of double precision floating point algorithms in use today.Dr. Mark extended this work to RLGs and multi-oscillator gyros throughout the 1980s enabling operation of strapdown navigation systems in very highly dynamic environments. The code, algorithms, and techniques developed at that time continue to be used today. In the late 1980s, with the advent of GPS, Dr. Mark was heavily involved in the development of the embedded GPS-inertial systems. During the 1990s, he was instrumental in developing the first production fiber-optic gyro systems as well as high performance redundant inertial measurement units for control of inherently unstable airframes such as the Eurofighter.