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What is Lidar?
Light Detection and Ranging (LIDAR) is a technology similar to RADAR that can be used to create high-resolution digital elevation models (DEMs) with vertical accuracy as good as 10 cm. LIDAR equipment, which includes a laser scanner, a Global Positioning System (GPS), and an Inertial Navigation System (INS), is generally mounted on a small aircraft. The laser scanner transmits brief laser pulses to the ground surface, from which they are reflected or scattered back to the laser scanner. Detecting the returning pulses, the equipment records the time that it took for them to go from the laser scanner to the ground and back. The distance between the laser scanner and the ground is then calculated based on the speed of light. While flying, the airplane’s position is determined using GPS, and the direction of the laser pulses are determined using the INS. Because one laser pulse may reflect back from multiple surfaces, such as the top of a tree, a house, and the ground surface, there are multiple returns from each pulse that can be used to map such things as the top of the tree canopy, buildings, and the ground. Post-processing is used to differentiate between these multiple returns to determine the bare-earth surface. Using the combined information from the laser scanner, the GPS, and the INS, very accurate, closely spaced (typically 1 per square meter) X, Y, Z coordinates are determined from which a DEM is be made.
-- Linda Mark USGS/Cascades Volcano Observatory, October 2004
Press release, October 25, 2004
-- [PDF format,32K]
Preliminary color map of elevation change at Mount St. Helens, September 2003 to October 4, 2004.
-- [PDF format,2.4M]
Area shown is 5.2 km x 5.2 km in size, or about 3.25 miles square. Please note that small elevation differences, between -0.4 and +1.4 meters, are not shown as most such small differences reflect differing geodetic frameworks for the September 2003 and October 4, 2004 surveys. These decrease with further analysis and processing.
Shaded relief images of Mount St. Helens showing volcanic unrest-related changes from September 2003 through November 20, 2004, including both still and animated versions.
LIDAR Images of Mount St. Helens, Washington
September 2003 through November 20, 2004, including animation
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[NASA/USGS image]
[click to enlarge]
Vertical view of new dome area Mount St. Helens crater, September 2003.
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[NASA/USGS image]
[click to enlarge]
Vertical view of new dome area Mount St. Helens crater, September 24, 2004.
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[NASA/USGS image]
[click to enlarge]
Vertical view of new dome area Mount St. Helens crater, September 30, 2004.
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[NASA/USGS image]
[click to enlarge]
Vertical view of new dome area Mount St. Helens crater, October 4, 2004.
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[NASA/USGS image]
[click to enlarge]
Vertical view of new dome area Mount St. Helens crater, October 14, 2004.
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[NASA/USGS image]
[click to enlarge]
Vertical view of new dome area Mount St. Helens crater, November 20, 2004.
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Animation, LIDAR images from:
September 2003
September 24, 2004
September 30, 2004
October 4, 2004
October 14, 2004
November 20, 2004
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LIDAR, September 2003 and October 4, 2004, with Animated Pairs
Shaded relief images of Mount St. Helens showing recent volcanic unrest-related changes, including both still and animated pairs.
Synthetic Fly-throughs of Mount St. Helens crater, October 4, 2004 .
Created using IKONOS 1 meter panchromatic satellite image draped on October 4, 2004 topography, in "mpg" or "mpeg" format. October 4, 2004 LIDAR imagery collected for NASA by TerraPoint USA, Inc. October 4, 2004 IKONOS satellite imagery from Space Imaging. Fly-through animations created by NASA Earth Observatory.
- Notes:
- September 2003 LIDAR was collected for the USGS by EarthData International.
- October 4, 2004 LIDAR was collected for NASA by TerraPoint USA, Inc. This data is still preliminary.
- IKONOS satellite imagery from Space Imaging.
- Contacts:
- USGS: Ralph A. Haugerud (rhaugerud@usgs.gov)
- NASA: David J. Harding (david.j.harding@nasa.gov)
- Information:
- Useful Links - LIDAR
- Other Menus of Interest
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