System and method for improving the accuracy of pressure altitude determinations in an inertial navigation system

Abstract

A system and method for improving the accuracy of altitude determinations in an inertial navigation system. Pressure measurements available to the inertial navigation system are used to initially calculate an estimated pressure altitude using the standard day model for the atmosphere. Temperature measurements are further utilized in the physical relationship between temperature, pressure, and altitude to compute a second computed altitude. A change between subsequent second computed altitudes is calculated and compared with a respective change in the computed pressure altitude in order to generate a correction value. The correction value is then used to modify the computed pressure altitude to generate a more accurate determination of the absolute altitude of the inertial navigation system. The correction value is utilized to account for changes in atmospheric conditions which may be encountered by an aircraft and to further reduce the effects of erroneous temperature and pressure measurements in subsequent altitude determinations. Thus, the system and method of the present invention provides an absolute altitude determination having improved stability and improved accuracy over prior systems.