A New Algorithm for Computing Inertial Altitude and Vertical Velocity

Inertial navigators determine inertial altitude and vertical velocity by a closed feedback loop in which the vertical accelerometer output is mixed with a pressure altitude reference. Pressure altitude is determined as a function of presure based on the standard atmosphere models. Since the atmosphere is almost always nonstandard, large inertial altitude and vertical velocity errors may result. A unique algorithm has been devised to compute a dynamically corrected altitude reference by numerically integrating the physical relation for a column of air as a function of pressure, gravity, and absolute temperature. The new algorithm has been flight tested and has been shown to yield accurate results.