NOAA REMOTE SENSING EXPERTISE AIDS WORLD TRADE CENTER RECOVERY
September 28, 2001 NOAA's
National Geodetic Survey and Aircraft
Operations Center mapped the wreckage of the World Trade
Center in support of recovery and cleanup efforts following the
Sept. 11 terrorist attack. The data are being used to provide
a very accurate geographic network. Building and utility engineers
will be able to determine the location of original foundation
support structures, elevator shafts, basement storage areas and
building utility connections enabling them to concentrate their
digging and recovery efforts in the proper location.
These images will also provide
very accurate height measurements as the recovery efforts descend
into the basement, to mitigate possible flooding from the surrounding
rivers as well as to determine the volume of debris and the reach
needed by cranes to remove it.
Click image for
larger view. Credit "NOAA."
(See graphic legend below.)
Click here for images
2 and 3.
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.
This was a partnership between
NOAA, Army Joint Precision Strike Demonstration, Optech Inc.
of Toronto, Canada, and the University of Florida. Optech and
the University of Florida processed the data which produced the
On the LIDAR image above the
following colors correspond
with the following elevations relative to mean sea level.
-9.272 to 0
-30.42 to 0
0 to 30
0 to 98.43
30 to 100
98.43 to 328.08
100 to 150
328.08 to 492.12
150 to 201.19
492.12 to 764.59
NOAA's efforts in New York
began on the ground on Sept. 15th as NGS field survey personnel
provided the necessary ground support and calibration expertise
for the airborne imaging sensorshigh resolution cameras
and laser ranging devices. These airborne and ground-based systems
will produce very accurate map products at ground zero and the
surrounding area affected by the terrorist attack. Both private
government agencies benefited from these activities.
team used the global positioning system (GPS)
to position both ground and airborne mapping sensors. GPS technology
fixes the latitude, longitude and height of a point on the ground
and in space within five centimeters. Additional support was
provided by the NGS Continuously Operating Reference Stations
(CORS) program, which
used two of its nearby continuously operating GPS sites to collect
data for the remote sensing missions.
Similar work was performed at the Pentagon on September 26-28.
Citation jet, N52RF, usually used for remote sensing and
high resolution photography for coastal mapping, was outfitted
with an Optech LIDAR
(Light Detection and Ranging). Collecting both LIDAR data
and high-resolution photography, the Citation flew over a five-square
kilometer area of lower Manhattan.
Flights over the World Trade
Center took place Sept. 23 and Sept. 26. There were two flights
lasting four hours each. The NOAA Citation jet flew at an altitude
of 5,000 to 6,000 feet.
The NGS field support team
included Mike Aslaksen, Ed Carlson, and Jason Woolard. The Citation
crew included Lt. Cmdr. Brad Kearse, Lt. Mike Weaver, and Lt.
Will O'Dell (pilots) of the NOAA
Commissioned Corps and Aircraft Operations Center; and Steve
Nicklas of NGS.
The U.S. Army Joint Precision
Strike Demonstration initiated and coordinated the entire effort.
Army JPSD worked closely with NOAA, Optech Inc. and the University
of Florida to produce the images and map products.
GIS Responds to Terrorism
Relevant Web Sites
Light Detection and Ranging (LIDAR) with sample images
NOAA's Coastal Aerial Photography
Citation Photos: 1,
Hernandez, NOAA, (202)
482-3091 or Jeanne
Kouhestani, NOAA Office
of Marine and Aviation Operations, (301) 713-3431 ext. 220