A computer system may elicit from a human observer ground truth data useful in automatically detecting one or more features in images. The elicitation may include presenting an image to a human observer that has a visual indicator in an image, the visual indicator indicating having a location and orientation with respect to the image; asking the human observer to judge whether a particular image feature is present in the image at the location and orientation indicated by the visual indicator; receiving input from the human observer indicative of whether the particular image feature is present at the location and orientation indicated by the visual indicator; storing the input received from the human observer as part of the human-labeled ground truth data; and repeating the process described above one or more times in connection with a visual indicator that has a different location or orientation with respect to the image or that uses a different image. The stored human-labeled ground truth data may have a content that is useful in automatically detecting one or more features in other images.