1999 Post Hurricane Floyd NOAA/USGS/NASA Airborne LiDAR Assessment of Coastal Erosion (ALACE) Project for the US Coastline

This data set includes data collected September 18, 1999 following Hurricane Floyd landfall in North Carolina. The

data covers the coastline starting in South Carolina and extended slightly into Virginia.

Laser beach mapping uses a pulsed laser ranging system mounted onboard an aircraft to measure ground

elevation and coastal topography. The laser emits laser beams at high frequency and is directed downward at the

earth's surface through a port opening in the bottom of the aircraft's fuselage. The laser system records the

time difference between emission of the laser beam and the reception of the reflected laser signal in the

aircraft. The aircraft travels over the beach at approximately 60 meters per second while surveying from

the low water line to the landward base of the sand dunes.

Original contact information:

Contact Org: NOAA Office for Coastal Management

Phone: 843-740-1202

Email: coastal.info@noaa.gov

This data was collected as part of an effort to map beach topography and assess beach change along the US coastline.

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This data set was collected with a LIDAR (LIght Detection And Ranging) instrument designed and developed by the Observational

Sciences Branch (OSB) of NASA at the Wallops Flight Facility in Virginia. The instrument, originally designed for mapping ice sheets

in Greenland, is called the Airborne Topographic Mapper or ATM. The ATM II (the latest version), operates with a Spectra Physics

laser transmitter, which provides a 7 nanoseconds long, 250 microjoules pulse at a frequency-doubled wavelength of 523 nanometers

in the blue-green spectral region. The laser transmitter can function at pulse rates from 2 to 10 kilohertz (kHz). The laser system

with a separate cooling unit weighs approximately 45 kilograms (kg) and requires approximately 15 amperes of power at 115 volts.

The transmitted laser pulse is reflected to the surface of the earth with the aid of a small folding mirror mounted on the back of a

secondary mirror of a rotating scan mirror assembly mounted directly in front of the telescope. The scan mirror, which is rotated at 20

hertz, is comprised of a section of round aluminum stock, machined to a specific off-nadir angle. A scan mirror with the off-nadir

angle of 15 degrees was utilized, producing an elliptical scan pattern with a swath width equal to 50 percent of the approximately

700-meter aircraft altitude. The reflected laser pulse is transmitted to a photo-multiplier assembly that consists of a lens, a

narrow bandpass filter, and a single photomultiplier tube.

Note: The Spatial Reference section of this document may lack fully FGDC-compliant information regarding projection parameters

(i.e., Central meridian, false Northing, etc.). The State Plane or UTM Zone will be supplied, and the corresponding parameters can be

found in Appendix C of: Snyder, John, 1987, Map Projections, a Working Manual (U.S. Geological Survey Professional Paper 1395):

Washington, U.S. Government Printing Office.