Importance

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Abstract

Systems are provided to derive a value of barometric pressure at a defined location in the atmosphere at a computed geometric height. By using the geometric height in a look-up table of pressure/height values representing a standard atmospheric profile, atmospheric deviation data indicative of the difference between measured and reference pressures at that atmospheric location (C) is derived. Ground-based interrogators (10,20) located at spaced positions are used to initiate response signals from airborne transponders commonly installed in transient aircraft (C). Using resulting range data based on round-trip timing differences in signals sent to (12,16) and received from (16,14) the airborne transponder (C), geometric analysis and computation is used (18) to determine the geometric height of the transponder representing a specific atmospheric location. The height, together with barometric pressure data transmitted by the airborne transponder, are used (28) for the look-up of reference pressure data and derivation of atmospheric deviation data for that atmospheric location. Systems and methods provide such data for inflight altimeter calibration, height determination, atmospheric pressure profile development, weather forecasting, transponder calibration and other purposes.

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First Claim