Litton Systems, Inc.

Dean E Lottman

Daniel A Tazartes

John G Mark

Brian T Lottman

A system and method for improving the accuracy of altitude determinations in an inertial navigation system. The system utilizes pressure measurements which are taken by a barometric altimeter and converted into an estimated pressure altitude using any known pressure-to-altitude conversion. A pressure correction value is then generated using a correction value generating formula that is a function of altitude. The pressure correction value is then multiplied by a pressure offset value for the barometric altimeter to generate a pressure offset error for the barometric altimeter. This pressure offset error is used in the present invention to modify the pressure altitude estimation in order to generate an altitude determination having an improved accuracy. The present invention further determines an amount of observation noise in the barometric altimeter that is a function of pressure noise and altitude, where the altitude estimation is further modified to account for the observation noise. Thus, the system and method of the present invention improves the accuracy of altitude determinations in inertial navigation system over prior systems by directly accounting for errors in pressure measurements taken by a barometric altimeter due to offset and noise.

System and method of compensating for pressure sensor errors and noise in inertial vertical loop data

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.

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Chatsworth, CA, United States of America

Dean E Lottman