A method for estimating a sub-pixel position of an extreme point in an image uses a parametric function. The parametric function is fitted locally to a group of neighboring pixels in the image, and a spatial position of an extreme point of the parametric function is identified. If the extreme point of the parametric function is of a different type than the extreme point in the image, or the position of the extreme point of the parametric function is located outside an area defined by the pixel positions in the group of neighboring pixels, a pixel is removed from the group of neighboring pixels and the fitting of the parametric function is repeated. In the end, the sub-pixel position is estimated as the position of the extreme point of the parametric function. A level of uncertainty of the estimated sub-pixel position is estimated as the number of repetitions needed before arriving at the estimate of the sub-pixel position.