Methods and apparatus for using image data to determine camera location and orientation

A method of measuring the absolute three dimensional location of a point D with respect to a coordinate system defined using three points, A, B and C, separated by known distances using image data comprising:

• a. capturing two images of a scene containing the points A, B, C and D, using one or more cameras of known principal distance,
• b. determining the location and orientation of said one or more cameras at the time each of said images was captured with reference to said coordinate system using information derived from said images, principal distance and said known distances, and
• c. using the locations of the one or more cameras at the time the images were captured to determine the location of said point D from image data by
• c1. defining an auxiliary coordinate system with origin along the line joining the locations of the cameras,
• c2. defining the center point of each image as an origin of a set of image reference axes pointing in X', Y' and Z' directions, respectively,
• c3. measuring offset in at least one of the X' and Y' directions of a point on the first image and of a corresponding point of a second image,
• c4. determining the angles formed between a line joining point D, the principal point of the objective and the image of point D on one of the X' or Y' planes for each of the images,
• c5. determining a distance h representing a distance of point d to a line joining principle points of said one or more cameras used to capture said two images using the measured offsets, the focal length and the angles,
• c6. determining the X' and Y' coordinates of point D in the auxiliary coordinate system, and
• c7. transforming coordinates (X', Y', h) of the auxiliary coordinate system to a representation in said coordinate system defined using said three points, A, B and C.

A method of measuring the absolute three dimensional location of a point D with respect to a coordinate system defined using three points, A, B and C, separated by known distances using image data comprising:

• a. capturing two images of a scene containing the points A, B, C and D, usinq one or more cameras of known principal distance,
• b. determining the location and orientation of said one or more cameras at the time each of said images was captured with reference to said coordinate system using information derived from said images, principal distance and said known distances by,
• b1. representing the distance between point A, B and C and the principal point of a camera O as a viewing pyramid,
• b2. modifying the representation of the pyramid to a three triangle flattened representation,
• b3. selecting a low estimate Ob.sup.1 for one interior side of a first triangle of said flattened representation,
• b4. solving the first triangle using image data, principal distance and said known distances, yielding, inter alia, a first calculated value for length OA, given estimate Ob.sup.1,
• b5. solving the second triangle using results obtained,
• b6. solving the third triangle using results obtained, yielding, inter alia, a second calculated value for length OA,
• b7. subtracting the second calculated value for length OA from the first calculated value for length OA to produce a difference value,
• b8. revising the value of estimate Ob.sup.1 by adding said difference value to achieve a revised estimate,
• b9. iterating steps d-h using the revised estimate until said difference value is less than a desired accuracy, and
• b10. deriving values for camera location using one or more sets of values for distances OA, OB and OC, and
• c. using the locations of the one or more cameras at the time the images were captured to determine the location of said point D from image data.

A method of measuring distance including vertical height comprising:

• a. measuring the absolute three dimensional location of points D, E and F with respect to a coordinate system defined using three points, A, B and C, separated by known distances using image data by:
• a1. capturing two images of a scene containing the points A, B, C, D, E and F, using one or more cameras of known principal distance,
• a2. determining the location and orientation of said one or more cameras at the time each of said images was captured with reference to said coordinate system using points A, B, and C from said images, principal distance and said known distances,
• a3. using the locations of the one or more cameras at the time the images were captured to determine the locations of said points D, E and F from image data,
• b. determining distances between points D, E and F, and
• c. using the location of said points D, E and F and the location of one or more cameras at the time images were captured to determine the location of other points.

Apparatus for measuring the absolute three dimensional location of a point D with respect to a coordinate system defined using three points, A, B and C, separated by known distances using image data comprising:

• a. one or more cameras for capturing images of a scene containing the points A, B, C and D,
• b. means for storing images captured by said one or more cameras,
• c. means for processing stored images to determine the location and orientation of said one or more cameras at the time each of said images was captured with reference to said coordinate system, using 3 to 5 points from said images, principal distance and said known distances,
• d. means for using the locations of said one or more cameras at the time the images were captured to determine the location of said point D from image data.