NOAA Images

October 30, 2001 — NOAA's aircraft flew five missions totaling more than 16 hours over the World Trade Center after the events of Sept. 11 to aid in the recovery efforts. NOAA's Citation jet mapped ground zero using aerial photography and Light Detection and Ranging (LIDAR) technology. The flights began Sept. 23 and ended Oct. 15. Each flight lasted about four hours. Teams from NOAA's National Geodetic Survey and Aircraft Operations Center worked on scene at the request of the U.S. Defense Department.

NOAA's jet also took high-resolution photos of the area. These photos show ground zero in great detail. It also allows the recovery crews to see how far debris fell from the site. The plane flew at an altitude of between 3,000 and 7,000 feet during its various fly-overs.

Digital Surface Models created by the LIDAR system provide very accurate 3-dimensional positioning of the building structures and the surrounding area. The 3-D models, in this case, have helped to locate original support structures, stairwells, elevator shafts, basements, etc. When this data is merged with the high resolution aerial photography taken by NOAA's Citation aircraft, it will create a very accurate image with relative accuracy around three decimeters.

The data collected by the LIDAR equipment helped to produce 3-D images of the site where crews continue their recovery and cleanup efforts. These images help to identify the height of the rubble so that the appropriate cranes can be used to remove it. The data collected from the fly-overs provide building and utility engineers the information needed to locate original foundation support structures, elevator shafts and basement storage areas. This allows the crews to pinpoint their digging and recovery efforts.