Laser technology helps track changes in mount st. hellens

Gretchen Cook-Anderson
Headquarters, Washington Oct. 25, 2004
(Phone: 202/358-0836)

Catherine Puckett
USGS, Western Region, Eureka, Calif.
(Phone: 707/442-1329)

RELEASE: 04-354

LASER TECHNOLOGY HELPS TRACK CHANGES IN MOUNT ST. HELENS

U.S. Geological Survey (USGS) and NASA scientists
studying Mount St. Helens are using high-tech Light Detection
and Ranging (LIDAR) technology to analyze changes in the
surface elevation of the crater, which began deforming in
late September 2004.

With data derived from airborne LIDAR, scientists can
accurately map, often in exquisite detail, the dimensions of
the uplift and create better models to forecast volcanic
hazards. LIDAR shows, in the two weeks before Oct. 4, the new
uplift grew to the height of a 35-story building (110 meters
or 360 feet) and the area of 29 football fields (130,000
square meters).

"This is the first time USGS and NASA have teamed to use
LIDAR to measure volcano deformation," said USGS scientist
Ralph Haugerud. He noted LIDAR technology enables researchers
to compare with greater accuracy than ever before the
topography before and after volcanic events. "The resulting
pictures of topographic change can reveal information found
in no other kind of data set," added David Harding, a
scientist at NASA's Goddard Space Flight Center, Greenbelt,
Md.

In 2003 the USGS contracted a LIDAR survey of Mount St.
Helens. In early September 2004, USGS and NASA scientists
began detailed planning for a second survey. The survey,
contracted by NASA, would extend the area covered by the
first survey. But when the mountain began rumbling on Sept.
23, USGS and NASA scientists accelerated plans and re-
surveyed the mountain on Oct. 4. The topographic changes
resulting from the unrest at Mount St. Helens are shown in
detail in the Oct. 4, 2004, LIDAR survey.

Some of the Mount St. Helens features related to the volcanic
unrest visualized in the new LIDAR-derived Digital Elevation
Model (DEM) include growth of a new volcanic dome south of
the 1980-1986 volcanic dome and new steam-and-ash vents.
Additional changes between the two LIDAR surveys unrelated to
the volcanic unrest include shrinking snow fields, several
rock falls, movement of three rock glaciers, and growth of
the crater glacier, which has been an ongoing subject of USGS
research at Mount St. Helens.

Comparison and analysis of the DEMs from the two surveys by
Haugerud and Harding show, as of Oct. 4, 2004, 5.3 million
cubic meters (6.9 million cubic yards) of volume change
occurred in the area of uplift. This analysis confirms
photogrammetric measurements made over the same period by the
USGS.

Linda Mark, a hydrologist with the USGS Cascades Volcano
Observatory, said "Global Positioning System data provide us
with very accurate point measurements of deformation, but
only at locations where we can place an instrument. LIDAR,
however, helps us quantify the ongoing deformation in the
crater of Mount St. Helens with lesser accuracy but over a
much broader area. Used together, the two methods complement
each other, and the LIDAR-derived DEMs can be used for
modeling efforts to help forecast volcanic hazards."

LIDAR mapping uses a scanning laser rangefinder mounted in a
small aircraft to measure distances from the aircraft to the
ground several tens of thousands of times each second. It
commonly measures the ground position at points a meter apart
with vertical accuracy as good as 10 centimeters (four
inches).

NASA scientists and engineers in the 1980s and 1990s
pioneered airborne LIDAR mapping, Harding said. "Because of
its very high accuracy and fast turn-around of results, LIDAR
is rapidly becoming the preferred method for detailed
topographic mapping and is conducted worldwide on a
commercial basis by numerous companies," he said.

For information, images and animations related to this story
on the Web, visit:

http://www.nasa.gov/vision/earth/loo.../mshelenslidar
..html


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Jacques :-)

www.spacepatches.info