Method for locating a target from an elliptical contour

A method for locating a target (C) relative to a vehicle (V), the target (C) comprising at least one three-dimensional external component (Cs) presenting a quadratic surface, the method being implemented by a computer and comprising:

• capturing an image (I) of the target comprising an area of interest (Z) in which the external component (Cs) of the target is visible in the form of an elliptical contour,
• for each of a plurality of pixels of the area of interest (Z) in the image, calculating an intensity gradient of the image around the pixel, and determining, based on the intensity gradient, the parameters of a line presenting a direction normal to the gradient at said pixel,
• selecting, among the set of determined lines, a set of lines that are tangents to the elliptical contour,
• estimating the parameters of the elliptical contour on the image based on the parameters of the tangents to the elliptical contour,
• wherein selecting lines that are tangents to the elliptical contour comprises:
• calculating, for each pixel, an angle formed by the line presenting a direction normal to the gradient at said pixel and by a line connecting said pixel to an estimated center of the elliptical contour, and
• selecting the line presenting a direction normal to the gradient at said pixel as a tangent to the elliptical contour if the calculated angle is equal to a right angle plus or minus a predetermined tolerance.