Aircraft ground velocity determination system

Claim 1

Apparatus for determining the ground velocity of an aircraft comprising: means for detecting from the aircraft a first radiant energy contour of a first area of the earth's surface and, after a time delay, a second radiant energy contour of a second area of the earth's surface, which second area overlaps in part with the first area; means for comparing said first contour with said second contour to produce a position shift signal which represents the relative contour position shift necessary to obtain the maximum degree of correlation between said first contour and said second contour; means for producing an altitude correction signal; means for multiplying said position shift signal by said altitude correction signal so as to produce a distance signal; and means for dividing said distance signal by said time delay to obtain a ground velocity signal of the aircraft.

Claim 27

An apparatus for determining the ground velocity of an aircraft comprising: a sensor which includes a plurality of photodetector pixels, each pixel generating an electrical signal which has its magnitude proportional to the intensity of incident radiant energy; means for enabling less than all the pixels to generate signals which represent a first light intensity contour of a first area of the earth's surface, and after a time delay, enabling the pixels which do not form part of said first light contour to generate signals which represent a second light intensity contour of a second area of the earth's surface which partially overlaps said first area, wherein said pixels forming said first contour are interspersed among said pixels forming said second contour; means for adjusting the time delay to control the degree of overlap between said first and second areas; means for controlling the exposure time of said pixels as a function of the time delay, aircraft altitude, and intensity of a light contour; means for registering said first and second contours; means for digitizing the magnitude of the signals representing said first and second contours; means for storing said first and second digitized contours; means for arranging said first and second digitized contours in an initial pixel-to-pixel orientation with respect to each other and for incrementally shifting said first digitized contour to a plurality of successive pixel-to-pixel positions relative to said second digitized contour; means for multiplying the values of the corresponding pixels of said first and second digitized contours and for summing the products of all corresponding pixels of said first and second digitized contours for each orientation of said plurality of positions; means for storing the sums of said products means for identifying the greatest sum obtained over said plurality of position shifts; means for producing a signal representing the number of successive position shifts necessary to obtain said greatest sum; means for generating an altitude correction signal; means for multiplying said number of shifts signal by said altitude correction signal to generate a ground distance signal of the aircraft; and means for dividing said distance signal by said time delay to generate an aircraft ground velocity signal.

Claim 28

An apparatus for determining the ground velocity of an aircraft comprising: a sensor which includes a plurality of photodetector pixels, each pixel generating an electrical signal which has its magnitude proportional to the intensity of incident radiant energy; means for enabling less than all the pixels to generate signals which represent a first light intensity contour of a first area of the earth's surface, and after a time delay, enabling the pixels which do not form part of said first light contour to generate signals which represent a second light intensity contour of a second area of the earth's surface which partially overlaps said first area, wherein said pixels forming said first contour are interspersed among said pixels forming said second contour; means for adjusting the time delay to control the degree of overlap between said first and second areas; means for controlling the exposure time of said pixels as a function of the time delay, aircraft altitude, and intensity of a light contour; means for registering said first and second contours; means for digitizing the magnitude of the signals representing said first and second contours; means for storing said first and second digitized contours; means for arranging said first and second digitized contours in an initial pixel-to-pixel orientation with respect to each other and for incrementally shifting said first digitized contour to a plurality of successive pixel-to-pixel positions relative to said second digitized contour; means for multiplying the values of the corresponding pixels of said first and second digitized contours and for summing the products of all corresponding pixels of said first and second digitized contours for each orientation of said plurality of positions; means for storing the sums of said products means for identifying the greatest sum obtained over said plurality of position shifts; means for producing a signal representing the number of successive position shifts necessary to obtain said greatest sum; means for generating an altitude correction signal; means for multiplying said number of shifts signal by said altitude correction signal to generate a ground distance signal of the aircraft; and means for dividing said distance signal by said time delay to generate an aircraft ground velocity signal.

Claim 31

A method for determining the ground velocity of an aircraft comprising: detecting from the aircraft a radiant energy contour of a first area of the earth's surface; after a time delay, detecting from the aircraft a radiant energy contour of a second area of the earth's surface which partially overlaps the first area; comparing the first contour with the second contour to produce a signal representing the relative contour position shift necessary to obtain the maximum degree of correlation between the first and second contours; producing an altitude correction signal; multiplying the contour position shift signal by the altitude correction signal to produce a distance signal; and dividing the distance signal by the time delay to generate a ground velocity signal.

Claim 32

A method for determining the ground velocity of an aircraft comprising: detecting from the aircraft a radiant energy contour of a first area of the earth's surface; after a time delay, detecting from the aircraft a radiant energy contour of a second area of the earth's surface which partially overlaps the first area; comparing the first contour with the second contour to produce a signal representing the relative contour position shift necessary to obtain the maximum degree of correlation between the first and second contours; producing an altitude correction signal; multiplying the contour position shift signal by the altitude correction signal to produce a distance signal; and dividing the distance signal by the time delay to generate a ground velocity signal.

Claim 33

A method for determining the ground velocity of an aircraft comprising: enabling a first set of photosensors mounted on the aircraft to form a first light intensity contour in response to light emitted and reflected from a first area of the earth's surface; after a time delay, enabling a second set of photosensors mounted on the aircraft to form a second light intensity contour in response to light emitted and reflected from a second area of the earth's surface which partially overlaps the first area; adjusting the time delay to control the degree of overlap of the first and second areas; controlling the time the photosensors are enabled as a function of the time delay, aircraft altitude, and average intensity of a previously formed contour; comparing the first and second contours to produce a signal representing the relative contour position shift necessary to attain the maximum degree of correlation between the first and second contours; generating an altitude correction signal; multiplying the relative contour shift signal by the altitude correction signal to produce a ground distance signal; and dividing the ground distance signal by the time delay to generate a ground velocity signal.

Claim 34

A method for determining the ground velocity of an aircraft comprising: enabling a first set of photosensors mounted on the aircraft to form a first light intensity contour in response to light emitted and reflected from a first area of the earth's surface; after a time delay, enabling a second set of photosensors mounted on the aircraft to form a second light intensity contour in response to light emitted and reflected from a second area of the earth's surface which partially overlaps the first area; adjusting the time delay to control the degree of overlap of the first and second areas; controlling the time the photosensors are enabled as a function of the time delay, aircraft altitude, and average intensity of a previously formed contour; comparing the first and second contours to produce a signal representing the relative contour position shift necessary to attain the maximum degree of correlation between the first and second contours; generating an altitude correction signal; multiplying the relative contour shift signal by the altitude correction signal to produce a ground distance signal; and dividing the ground distance signal by the time delay to generate a ground velocity signal.