Three federal agencies are collaborating on a coastline mapping project used this month to help determine Hurricane Bonnie's impact on North Carolina's dunes and other coastal structures.
NASA, the National Ocean-ic and Atmospheric Administration and the U.S. Geological Survey have teamed up to collect and proc-ess data, which is used to create detailed maps and cross-sectional diagrams of the coastline. State and local land managers use the material to decide zoning issues and determine the location and extent of dredging projects.
NASA and NOAA scientists collected data from the coasts of Virginia, North Carolina and South Carolina during the first week of September. They will turn the data over to USGS coastal geologists, who will conduct ground surveys of impacted areas to verify the data. The scientists will compare this data with existing topographical maps to assess any changes brought about by the storm.
The NASA Wallops Flight Facility, Wallops Island, Va., originally developed the laser beach-mapping technology to monitor changes in the polar ice caps, said Bill Krabill, NASA's project scientist for arctic ice mapping in Greenland. The laser can map in a week what would take months to map using traditional surveying methods, he said.
The 6-year-old polar ice cap mapping project uses NASA's Airborne Topographic Mapper, which is a laser altimeter that sends out a beam over a 300-kilometer swath of beach from a NOAA aircraft flying at about 109 mph.
This beam hits a target on the surface and bounces some of the energy back to the plane, Krabill said. The laser system scans and collects 5,000 samples per second. "We produce incredibly dense measurements of the topography as we fly along," he said.
Laser Altimeter Meets GPS
The laser altimeter system is precise enough to detect a formation as small as a basketball, Krabill said. It works by measuring the time it takes the pulse of energy to bounce back, determining the distance— within 2 inches— between the beach and the plane.
But scientists still need to know the exact location of the plane to correlate that data. That is where the Global Positioning System comes in, Krabill said. GPS receivers, one on the plane and one on the ground, tell the scientists the location of the aircraft within 2 inches, he said.
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