Patent ID: 6462703
Filing Date: 2002-10-08
Classification: G01C,G01S

Abstract:
A method for determining a barometric pressure corrected above mean sea level (MSL) altitude of an in-flight aircraft over terrain, comprising the steps of:calculating a current above ground level (AGL) altitude of the aircraft by generating a single brief transmission from the aircraft directed onto local terrain over which the aircraft is currently flying and receiving at the aircraft a return reflection of the transmission; identifying the current local terrain using then-current position coordinates of the aircraft, and determining a known MSL elevation of the identified local terrain using a source of stored terrain elevation data; calculating an actual MSL altitude of the aircraft from the calculated AGL altitude of the aircraft and the identified MSL elevation of the local terrain; determining an uncorrected MSL altitude estimate of the aircraft from static air pressure measurement; calculating a local barometric correction factor for the identified local terrain from the difference of said calculated actual MSL altitude of the aircraft and said determined MSL altitude estimate of the aircraft; and using the calculated correction factor in conjunction with continued measurement of static air pressure to determine the barometric pressure corrected MSL altitude of the in-flight aircraft proximate the identified local terrain and continuously as the aircraft proceeds in flight away from the local terrain.