摘要 |
A method and apparatus for performing on-board corrections to the computed navigation variables of an inertial system on an aircraft while flying over a body of water. Onboard instruments, including a barometric altimeter and a radar altimeter, measure the vertical distance of the aircraft above an ellipsoidal model of the earth and above the body of water respectively. An on-board computer calculates the differences between such heights over a plurality of points along the path the aircraft travels over the water as indicated by its inertial navigation system. The differences are compared with a map of the undulation of the geoid encompassing the region to determine the deviation of the navigated course from the true course. Appropriate corrections to the aircraft's inertial system may then be made to reduce error.
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