SLAM techniques allow reconstruction of a scene from video+position data. As the aircraft takes video of the terrain, it is logging its position. Large-scale ba

SLAM techniques allow reconstruction of a scene from video+position data. As the aircraft takes video of the terrain, it is logging its position. Large-scale batch processing can recover the 3D positions for each image feature that will minimize some error metric. Rural areas probably have lower-quality image data (or noisier aircraft position data).