Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
1999-07-06
2001-05-15
Nguyen, Tan (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S214000, C342S064000
Reexamination Certificate
active
06233522
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to aircraft positioning systems, and more particularly to a system and method for validating a position of an aircraft with cross-referenced information sources.
A major cause of aircraft accidents is the failure of an aircraft's positioning systems to adequately alert pilots of their true position, especially relative to variations in the terrain around them, such as with hills and mountains. Recent advances in aircraft navigation systems have done much to alleviate the problem of making a pilot aware an aircraft's position relative to terrain elements. Specifically, U.S. Pat. No. 5,839,080, owned by AlliedSignal, describes a terrain awareness system (TAS) to alert a pilot to terrain threats within a proximity of the aircraft. Further, Allied Signal's Enhanced Ground Proximity Warning System (EGPWS) provides a display of potentially hazardous terrain in an area surrounding a position of the aircraft as that position is reported by the flight management system (FMS) and/or other on-board navigation systems, such as a global positioning system (GPS) receiver. The terrain data is retrieved from a terrain database, such as a digital terrain elevation database (DTED).
Two sources of error may exist in conventional aircraft positioning systems. First, there may be errors in the terrain database. Second, there may be errors in the aircraft's reported position.
SUMMARY OF THE INVENTION
The present invention solves the problems of the prior art by utilizing an aircraft radar and a terrain database to correlate aircraft position information. The present invention can also use terrain data gathered from the aircraft radar to correlate and verify the data stored in a terrain database.
According to one aspect of the present invention an aircraft radar is utilized to obtain terrain reflectivity data. The terrain reflectivity data is then compared to terrain data stored in a terrain data base using a test statistic. The test statistic indicates the degree to which the radar terrain reflectivity data and the terrain data base data agree.
According to another aspect of the present invention, the invention utilizes an aircraft weather radar obtain the terrain radar reflectivity data. Use of the weather radar eliminates the need for separate dedicated radar and the additional cost and weight penalties associated therewith.
According to yet another aspect of the present invention, the invention further includes a tilt management system and/or method. The tilt management system permits the radar tilt angle to be set for optimal scanning of the terrain. The tilt management system also reduces pilot workload by avoiding the need to manually set the tilt.
According to still another aspect of the present invention, the present invention includes a scan interleaving function that permits the weather radar to scan for weather on certain sweeps and for terrain on other sweeps. The interleaving and tilt management function maximizes the utilization of the weather radar and automates the terrain data collection process, while not compromising the collection of weather data.
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patent: 5945926 (1999-08-01), Ammar et al.
patent: 6076042 (2000-06-01), Tognazzini
Allied-Signal Inc.
Nguyen Tan
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