Tracking objects with markers
First Claim
1. A method comprising computing the spatial location and azimuth of an object from the locations, in a single camera image, of exactly two points on the object, and information about an orientation of the object.
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Abstract
The spatial location and azimuth of an object are computed from the locations, in a single camera image, of exactly two points on the object and information about an orientation of the object. One or more groups of four or more collinear markers are located in an image, and for each group, first and second outer markers are determined, the distances from each outer marker to the nearest marker in the same group are compared, and the outer marker with a closer nearest marker is identified as the first outer marker. Based on known distances between the outer markers and the marker nearest the first outer marker, an amount of perspective distortion of the group of markers in the image is estimated. Based on the perspective distortion, relative distances from each other point in the group to one of the outer markers are determined. Based on the relative distances, the group is identified.
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Citations
42 Claims
- 1. A method comprising computing the spatial location and azimuth of an object from the locations, in a single camera image, of exactly two points on the object, and information about an orientation of the object.
- 25. A set of groups of markers, each group comprising four or more collinear markers, arranged such that the ratio of the distances between three fixed base markers is the same for each group in the set.
- 27. An apparatus comprising a group of markers arranged in a pattern that is uniquely identifiable by a single camera, comprising a linear pattern of four or more markers in which three base markers at the ends have a fixed geometry and one or more additional markers between the ends uniquely distinguish the group from other groups having the same base marker geometry.
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36. A method comprising
in an image, locating one or more groups of four or more collinear markers, and for each group, determining first and second outer markers, comparing the distance from each outer marker to the nearest marker in the same group, and identifying as the first outer marker the outer marker with a closer nearest marker, based on known distances between the outer markers and the marker nearest the first outer marker, estimating an amount of perspective distortion of the group of markers in the image, based on the perspective distortion, determining relative distances from each other point in the group to one of the outer markers, and based on the relative distances, identifying the group.
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37. The method of 36 wherein identifying the group comprises identifying a code value based on the distances from each other point in the group to one of the outer markers, and identifying one of a known set of groups that most closely corresponds to the code value.
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41. A method comprising
receiving coordinate information for images, on an imaging device of a camera, of two points on an object, receiving pitch information from a sensor on the object, using the coordinate information and the pitch information to obtain candidate values for the azimuth of the object, selecting one azimuth value based on an evaluation of the candidate azimuth values in equations relating the coordinate information and pitch information to distances of the points from the camera.
Specification