A method to provide a target image for evaluation with an object detector configured to detect objects of a specific object type, the method comprises: - obtaining a source image captured by a fisheye camera and depicting one or more objects in a scene, wherein the camera is mounted to capture images of the scene from above; - combining an inverse dewarping transform T -1 dewarp with an inverse pixel transform T -1 (d t) into a full inverse transform T -1 dewarp (T -1 (d t)), wherein the inverse dewarping transform T -1 dewarp depends on the type of fisheye camera and wherein the inverse pixel transform T -1 (d t) as a function of a distance dt from a principal point Pt of the target image to the target pixel to which the inverse pixel transform T -1 (d t) is applied, is given by T − 1 d t = exp dt − b / a if d t > d cutoff and T − 1 d t = d t if d t ≤ d cutoff; and wherein a = c / log z 1 / z 2; b = d cutoff − a log d cutoff; c is a parameter specifying a size in the target image of an object of the specific object type and is set to c = [(d cutoff)(z 0 /z 2)] - [(d cutoff)(z 0 /z 1)] to make the object at the distance d cutoff in the source image and in the target image of equal size; z 0 is an assumed height above ground of a center of an object of the specific type and is given by (z 1 +z 2)/2; z 1 is the camera mounting height above ground; z 2 is the camera mounting height above ground minus the assumed object height; and d cutoff is a distance threshold value at which an object of the specific object type in the source image will have the same size as the object of the specific object type in the target image; - applying the full inverse transform T -1 dewarp (T -1 (d t)) to each target pixel of a target image to determine one or more source pixels located at a position in the source image corresponding to a position of each target pixel in the target image; - assigning, to each target pixel, a target pixel value determined based on one or more source pixel values of the determined one or more source pixels located at the corresponding position, thereby is the size c in the target image of depicted one or more objects of the specific object type normalized in at least one size dimension of the depicted one or more objects of the specific object type; and - providing the target image to the object detector for evaluation. - obtaining a source image captured by a fisheye camera and depicting one or more objects in a scene, wherein the camera is mounted to capture images of the scene from above; - combining an inverse dewarping transform T -1 dewarp with an inverse pixel transform T -1 (d t) into a full inverse transform T -1 dewarp (T -1 (d t)), wherein the inverse dewarping transform T -1 dewarp depends on the type of fisheye camera and wherein the inverse pixel transform T -1 (d t) as a function of a distance dt from a principal point Pt of the target image to the target pixel to which the inverse pixel transform T -1 (d t) is applied, is given by T − 1 d t = exp dt − b / a if d t > d cutoff and T − 1 d t = d t if d t ≤ d cutoff; and wherein a = c / log z 1 / z 2; b = d cutoff − a log d cutoff; c is a parameter specifying a size in the target image of an object of the specific object type and is set to c = [(d cutoff)(z 0 /z 2)] - [(d cutoff)(z 0 /z 1)] to make the object at the distance d cutoff in the source image and in the target image of equal size; z 0 is an assumed height above ground of a center of an object of the specific type and is given by (z 1 +z 2)/2; z 1 is the camera mounting height above ground; z 2 is the camera mounting height above ground minus the assumed object height; and d cutoff is a distance threshold value at which an object of the specific object type in the source image will have the same size as the object of the specific object type in the target image; c is a parameter specifying a size in the target image of an object of the specific object type and is set to c = [(d cutoff)(z 0 /z 2)] - [(d cutoff)(z 0 /z 1)] to make the object at the distance d cutoff in the source image and in the target image of equal size; z 0 is an assumed height above ground of a center of an object of the specific type and is given by (z 1 +z 2)/2; z 1 is the camera mounting height above ground; z 2 is the camera mounting height above ground minus the assumed object height; and d cutoff is a distance threshold value at which an object of the specific object type in the source image will have the same size as the object of the specific object type in the target image; - applying the full inverse transform T -1 dewarp (T -1 (d t)) to each target pixel of a target image to determine one or more source pixels located at a position in the source image corresponding to a position of each target pixel in the target image; - assigning, to each target pixel, a target pixel value determined based on one or more source pixel values of the determined one or more source pixels located at the corresponding position, thereby is the size c in the target image of depicted one or more objects of the specific object type normalized in at least one size dimension of the depicted one or more objects of the specific object type; and - providing the target image to the object detector for evaluation.