Vehicle navigation
First Claim
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1. A method of measuring vehicle motion using an electro-magnetic radiation sensor having a field of view external to the vehicle and a distance measuring system, including the steps of:
- (a) selecting a first plurality of image points in the external field of view,(b) measuring and recording the bearings, relative to a fixed axis of the sensor, of the first plurality of image points at a first time,(c) measuring and recording the bearings, relative to the fixed axis of the sensor, of a second plurality of image points in the external field of view at a second time which respectively correspond to the first plurality of image points,(d) using the sets of bearings at the first and second times to calculate the apparent movement, relative to the sensor, of the second plurality of image points with respect to the corresponding ones of said first plurality of image points, and (e) using the apparent movement of the second plurality of image points relative to said first plurality of image points to calculate the direction of motion of the vehicle.
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Abstract
An aircraft navigation system uses an infra-red scanner to provide an image of the ground, and a laser doppler system to measure the speed of the aircraft relative to the ground. The apparent movement relative to the aircraft of features in the image is extrapolated to find the point in the image at which this movement converges. This point corresponds to the direction in which the aircraft is moving. Knowing the original position, the direction and motion of the aircraft, its new position can be calculated.
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Citations
17 Claims
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1. A method of measuring vehicle motion using an electro-magnetic radiation sensor having a field of view external to the vehicle and a distance measuring system, including the steps of:
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(a) selecting a first plurality of image points in the external field of view, (b) measuring and recording the bearings, relative to a fixed axis of the sensor, of the first plurality of image points at a first time, (c) measuring and recording the bearings, relative to the fixed axis of the sensor, of a second plurality of image points in the external field of view at a second time which respectively correspond to the first plurality of image points, (d) using the sets of bearings at the first and second times to calculate the apparent movement, relative to the sensor, of the second plurality of image points with respect to the corresponding ones of said first plurality of image points, and (e) using the apparent movement of the second plurality of image points relative to said first plurality of image points to calculate the direction of motion of the vehicle. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 16)
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11. A vehicle motion measurement system comprising;
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an electro-magnetic radiation sensor having a field of view external to the vehicle, means for selecting a plurality of image points in the external field of view at a specified time. a distance measuring system for measuring and recording the bearings, relative to a fixed axis of said sensor, of each of said plurality of image points selected at said given time, and computing means for operating on the data produced by said radiation sensor and by said distance measuring system at a first time to select a first plurality of image points in said external field of view at a first time, measure and record the bearings, relative to the fixed axis of said sensor, of said first plurality of image points, said means for selecting then determining a second plurality of image points which correspond to respective ones of said first plurality of image points, said distance measuring system operating to measure and record the bearings, relative to said fixed axis of said sensor, of said second plurality of image points, said computing means operating on the bearings measured for said first plurality of image points and for said second plurality of image points at said first time and said second time to calculate the apparent movement, relative to said sensor, of said second plurality of image points relative to said first plurality of image points, and using the apparent movement of said image points to calculate the direction of motion of the vehicle. - View Dependent Claims (12, 13, 14)
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17. A method of measuring vehicle motion using an elector-magnetic radiation sensor having a field of view external to the vehicle, a feature selector, a point selector, a tracker, and a distance measuring system, including the steps of:
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(a) using the radiation sensor to obtain a first external field of view at a first time, (b) using the feature selector to identify a plurality of image points in the external field of view which meet predetermined criteria, (c) using the point selector to select, from among the plurality of image points identified by said feature selector, a plurality of selected image points in the external field of view, (d) using the tracker to measure and record the bearings of the selected image points in the first external field of view relative to a fixed axis of the sensor, (e) using the radiation sensor to obtain a second external field of view at a second time, (f) using the feature selector and the tracker to identify a second plurality of image points in the second external field of view which correspond to the selected image points determined in the first external field of view, (g) using the tracker to measure and record the bearings, relative to the fixed axis of the sensor, of the second plurality of image points determined in step (f), (h) using the set of bearings of the selected image points in the first external field of view and the bearings of the second plurality of image points in the second external field of view, which were determined at said first and second times, to calculate the apparent movement of the second plurality of image points determined at step (f) relative to the corresponding ones of the selected image points determined at step (b), and (i) using the apparent movement of the image points to calculate the direction of motion of the vehicle.
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Specification