초록 ▼

A drift correction mechanism for a vehicle (e.g. aircraft) navigation system makes use of a digital map data base, in order to correct for errors in position estimates, so that the estimated flight path of the aircraft will more closely track its actual flight path, and thereby effectively compensat

A drift correction mechanism for a vehicle (e.g. aircraft) navigation system makes use of a digital map data base, in order to correct for errors in position estimates, so that the estimated flight path of the aircraft will more closely track its actual flight path, and thereby effectively compensate for the long term error to which the navigation system is subjected. During the flight, altimeter readings are periodically carried out in order to generate elevation values that are representative of the actual elevation of the terrain over which the aircraft is flying. These elevation values are then used as inputs to a digital map database, from which elevation profile contour lines of respective elevation values may be derived. At the time that a respective altimeter reading is effected, the position estimate output of the aircraft\s navigation system is also sampled. This position estimate is then compared with the contour line that passes through the actual position of the aircraft at the time the altimeter measurement is made. The separation between the navigation system\s position estimate and that geographical position on the contour line which is closest to the position estimate is then used as a correction factor to update the position estimate to a set of corrected geographical coordinates that more closely approximate the coordinates of the actual flight path of the aircraft.

대표청구항 ▼

For use with a vehicle navigation system in which position estimate output signals representative of an estimate of the position of a vehicle to terrain over which said vehicle is travelling are produced by said navigation system, an arrangement for adjusting said output signals to be representative

For use with a vehicle navigation system in which position estimate output signals representative of an estimate of the position of a vehicle to terrain over which said vehicle is travelling are produced by said navigation system, an arrangement for adjusting said output signals to be representative of an estimate of the position of said vehicle that more closely tracks the actual travel path of said vehicle comprising: first means for measuring the elevation of the terrain over which said vehicle is travelling and generating first signals representative of said elevation; second means, responsive to said first signals generated by said first means, for deriving from a terrain map data base second signals representative of a terrain contour line that follows an elevation profile containing the elevation represented by said first signals; third means, coupled to said navigation system, for deriving therefrom third signals representative of the estimated position of said vehicle at the time its elevation is measured by said first means; fourth means, coupled to said second and third means, for generating fourth signals representative of the separation between estimated position of said vehicle as represented by said third signals and the closest position thereto on said terrain contour line as represented by said second signals; and fifth means, coupled to said third and fourth means, for adjusting said third signals in accordance with said fourth signals, so as to produce said output signals representative of an estimate of the position of said vehicle that more closely approximates the actual position of said vehicle at the time that said first means carries out said elevation measurement.