Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Aeronautical vehicle
Reexamination Certificate
2000-03-13
2001-07-03
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Aeronautical vehicle
C701S207000, C701S208000
Reexamination Certificate
active
06256559
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the field of aircraft altitude determination as accomplished electronically from within the considered aircraft by a passive, non signal emitting and global positioning system signal-based technique.
The conventional radar altimeter transmits a radar signal from its host aircraft to the ground and processes a reflected or returned radar signal to determine the altitude of the host aircraft. A transmitted signal of this nature can, however, be detected by hostile persons to reveal the presence of the aircraft and to provide guidance for ordnance intended to intercept the aircraft. Similar non-atmospheric pressure altitude measuring arrangements based on electromagnetic energy of differing wavelengths including, for example, laser energy emissions are possible under some weather conditions but have the related disadvantages of being detectable and providing ordnance target identification. The present invention provides an uncomplicated measurement of aircraft altitude free of these signal emission and target identification disadvantages. The invention employs signals readily available in most parts of the world and makes additional use of some apparatus possibly already available on the host aircraft.
SUMMARY OF THE INVENTION
The present invention provides a passive, global positioning system signal-operated altitude determination for an aircraft. The invention uses the global positioning system signals received at a pair of locations on the host aircraft and signal processing based on ground reflection of one received signal together with simple geometric relationships between reflected and direct signals to determine the distance between the host aircraft and the earth.
It is an object of the present invention, therefore, to provide a passive electronic altimeter for an aircraft.
It is another object of the invention to provide a global positioning system signal operated aircraft altimeter.
It is another object of the invention to provide a non signal-emitting electronic altimeter for a military aircraft.
It is another object of the invention to provide an aircraft altimeter based on the relationship between directly incident and reflected global positioning system signals received from a satellite in earth orbit.
It is another object of the invention to provide a confirming non atmospheric pressure-related altitude determination for an aircraft.
It is another object of the invention to provide an accurate low-cost radio altimeter usable in a variety of large and small aircraft types.
It is another object of the invention to provide a global positioning system signal-enabled aircraft altimeter operable with either a single or a plurality of global positioning system signals.
Additional objects and features of the invention will be understood from the following description and claims and the accompanying drawings.
These and other objects of the invention are achieved by the combination of:
a host aircraft having first and second global positioning system signal reception antennas disposed on opposite extremities thereof, said first and second antennas having direct signal and earth-reflected signal reception capabilities respectively with respect to radio frequency signals originating in a global positioning system satellite;
radio frequency signal receiver apparatus connected with said first and second global positioning system signal reception antennas and generating output signals representing first and second samples of global positioning system data received from said global positioning system satellite via said first and second antennas respectively;
signal processing apparatus connected with said radio frequency signal receiver apparatus and generating, from said first and second samples of global positioning system data, first distance signals representative of direct physical distance between said aircraft first global positioning system signal reception antenna and said satellite and second distance signals representative of greater ground reflection-inclusive indirect physical distance between said aircraft second global position system signal reception antenna and said satellite;
said second distance signals representative of greater ground reflection-inclusive indirect physical distance between said aircraft second global positioning system signal reception antenna and said satellite including equal-angled incident and reflected signal paths to and from an earth point of satellite signal illumination attending said aircraft: and
geometric algorithm signal processing apparatus generating from said first and second distance signals and angular relationships attending said equal-angled incident and reflected signal paths an aircraft altitude signal representative of orthogonal distance between said aircraft and a ground point below said aircraft.
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Cuchlinski Jr. William A.
Hollins Gerald B.
Kundert Thomas L.
Marc-Coleman Marthe
The United States of America as represented by the Secretary of
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