Changes between the pre- and post-Ivan lidar surveys draped over topography: The two topographic surveys shown above have been differenced showing vertical change; red indicates a decrease in elevation and green indicates an increase. This vertical change has been draped over the post-Ivan topography. The houses that survived the storm are white, indicating no change. The houses that were destroyed are red, indication loss of elevation. Note the two green mounds behind the loss homes in the center of the image. This indicates that some homes were washed off their foundations and were moved inland, thus showing as a vertical gain in the lidar comparison.
Before and after Ivan photographs of the area within the rectangle drawn on the lidar images. These are U.S. Geological Survey photographs. [larger version]