Coupling ground-level panoramas and aerial imagery for change detection. Issue 3 (2nd July 2016) - Ghouaiel, Nehla
Abstract: Geographic landscapes in all over the world may be subject to rapid changes induced, for instance, by urban, forest, and agricultural evolutions. Monitoring such kind of changes is usually achieved through remote sensing. However, obtaining regular and up-to-date aerial or satellite images is found to be a high costly process, thus preventing regular updating of land cover maps. Alternatively, in this paper, we propose a low-cost solution based on the use of ground-level geo-located landscape panoramic photos providing high spatial resolution information of the scene. Such photos can be acquired from various sources: digital cameras, smartphone, or even web repositories. Furthermore, since the acquisition is performed at the ground level, the users' immediate surroundings, as sensed by a camera device, can provide information at a very high level of precision, enabling to update the land cover type of the geographic area. In the described herein method, we propose to use inverse perspective mapping (inverse warping) to transform the geo-tagged ground-level 360 photo onto a top-down view as if it had been acquired from a nadiral aerial view. Once re-projected, the warped photo is compared to a previously acquired remotely sensed image using standard techniques such as correlation. Wide differences in orientation, resolution, and geographical extent between the top-down view and the aerial image are addressed through specific processing steps (e.g. registration). Experiments on publicly available data-sets made of both ground-level photos and aerial images show promising results for updating land cover maps with mobile technologies. Finally, the proposed approach contributes to the crowdsourcing efforts in geo-information processing and mapping, providing hints on the evolution of a landscape.