Height measurement apparatus
AssigneeBAE SYSTEMS plc
InventorDavid R Parker
Life of this patent
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Abstract
Apparatus and methods for enhancing the accuracy of height above ground measurements in which the registration error between successive images taken of the terrain over which an aircraft is flying is minimised, the earlier image having first been transformed according to measurements of the aircraft linear and angular velocities, the focal length and attitude of the image sensing means, and an initial, coarse height estimate. By an iterative process, a more accurate height estimate is obtained.
Claims9
Apparatus for enhancing the accuracy of height above ground measurements comprising imaging sensor means for providing successive images of the terrain over which the apparatus is moved, storage means for storing at least temporarily two successive images, transformation means for transforming the earlier of said two successive images into a transformed image according to the linear and angular velocities of the apparatus, to the attitude of the imaging sensor means relative to the horizontal plane and to the focal length of the imaging sensor means, and to an estimated height above ground measurement, and means for comparing the transformed image with the latter of said two successive images and for estimating the registration error therebetween, means being provided for generating estimated height above ground measurements so as to reduce the registration error.
A method of enhancing the accuracy of height above ground measurements for an estimator moving over the ground, the method comprising:
- a) sensing two successive images of the terrain over which the estimator is moving;
- b) generating an approximate measurement of the height above ground;
- c) transforming the earlier of said two successive images into a transformed image, according to the linear and angular velocities of the estimator, to the attitude relative to the horizontal plane and the focal length of the image sensing means, and to an estimated height above ground measurement;
- d) comparing the transformed image with the later of said two successive images and estimating the registration error therebetween, and
- e) producing a second transformed image of the earlier of said two successive images according to an second estimated height above ground measurement in order to reduce said registration error.
Dependencies are inferred from the claim text.