A study conducted at Aston University has discovered distinctions in how seasoned Ordnance Survey (OS) mapmakers and beginners interpret aerial images for mapmaking. This finding has the potential to enhance the training procedures for new employees. Ordnance Survey (OS) is recognized for its travel and walking maps, as well as its role in maintaining Great Britain’s national g.Geographic database. When a building is demolished or developed, or a new road and path built, the map needs to be updated. Aerial photographs are taken of the area that has changed, either from a plane or using drones, and expert mapmakers, known as remote sensing surveyors, will examine the images to identify change and accurately redraw the map of the area. Image pairs are presented stereoscopically, one to each eye, allowing the remote sensing surveyors to see in 3D and correctly assess the topography, such as ditches, hills, and hedges. Led by Professor Andrew Schofield, a team from Aston University’s College of Health.Dr. Isabel Sargent, in collaboration with the School of Earth and Life Sciences, conducted a study to explore how remote sensing surveyors perceive shadows and highlights in images. The research involved six experienced surveyors and six beginners who were asked to evaluate 10,000 stereoscopic aerial images of hedges and ditches. These images were intentionally distorted to make the assessment challenging. Typically, aerial surveyors use stereoscopic images to create maps, and these images are captured on sunny days. Despite the natural inclination of the human brain to perceive light as coming from above, the orientation of light in the OS aerial images varies.The sun’s position plays a significant role in the way light is perceived by surveyors in the UK, who are located north of the equator. The light appears to come from the south, which makes it seem like it is coming from below in the images seen by the surveyors. The researchers conducted a study to understand how altering the direction of the light would impact the surveyors. Professor Schofield and the team conducted trials where they swapped the image pairs between the eyes, resulting in hedges looking like ditches and vice versa. Additionally, the direction of the light source was changed by vertically flipping the images in half of the trials. It was observed that expert surveyors heavily relied on the stereoscopic cues.The study focused on the effect of visual disparity on the ability to discern the shape and relief of an object. Novice participants tended to rely on lighting cues such as highlights and shadows and typically assumed that the light source was from above. As a result, they frequently made errors when presented with manipulated images. In contrast, experts demonstrated greater accuracy, even when the images were inverted, and some had adapted to assuming that the light source was from the south or below. This study is the first to demonstrate the natural inclination to perceive light as coming from above, which is prevalent among novices.The experts suggest that long-term experience can lead to changes in the way any animal species perceives visual stimuli. They believe that this finding could be utilized to create new visual training methods for remote sensing surveyors. For instance, undergoing intense and repeated exposure to challenging images may enhance performance through a process known as perceptual learning.
Professor Schofield expressed his enthusiasm about this outcome, stating:
“This is a very promising discovery. While others have demonstrated that the light-from-above assumption can be slightly altered, no one has previously observed complete reversals after extended periods of experience.
Dr. Sargent added:
“This finding will be beneficial for Ordnance Survey.”to comprehend the skills of their staff and enhance surveyor training and procedures.”
Andy Ormerod, a remote sensing surveyor involved in the research, stated:
“This study demonstrates that experienced remote sensing surveyors have a different perspective on the world. While non-surveyors are accustomed to seeing the world from one angle, our brains have adapted to perceive the world as seen from aerial imagery.”
Journal Reference:
- Emil Skog, Timothy S. Meese, Isabel M. J. Sargent, Andrew Ormerod, Andrew J. Schofield. Classification images for aerial images capture visualThe article “Expertise for binocular disparity and a prior for lighting from above” was published in the Journal of Vision in 2024, volume 24, issue 4, on page 11. The DOI for the article is 10.1167/jov.24.4.11.