Press Release

Complete Global Topographic Data Set Generated by NASA and the National Imagery and Mapping Agency

By SpaceRef Editor
August 22, 2003
Filed under , ,
Complete Global Topographic Data Set Generated by NASA and the National Imagery and Mapping Agency
NIMA

A brand new look and understanding of the place we call
home. That’s what you’ll get in a complete global
topographic data set generated by NASA and the National
Imagery and Mapping Agency (NIMA).

Produced by the Shuttle Radar Topography Mission, the global
data set, called “SRTM30,” greatly improves maps of Earth’s
land mass located between 60 degrees north and 60 degrees
south of the equator. That’s roughly from the southern tip
of Greenland to below the southern tip of South America.

Until now, the primary source of digital elevation data for
scientists and analysts involved in global studies has been
the U.S. Geological Survey’s “GTOPO30,” published in 1996,
it consists of elevation measurements spaced every 30-arc-
seconds. An arc-second is a measure of latitude and
longitude used by geographers that corresponds to about 928
meters, or 1,496 feet at the equator. This allows
identification of features roughly the size of Disneyland in
California. The SRTM30 map matches the GTOPO30 resolution,
but with its seamless quality, the map represents a leap in
global-scale accuracy.

“SRTM30 is a powerful demonstration of the benefits which
accrue from NASA’s human space flight program and satellite
radar mapping technology,” said John LaBrecque, manager,
Solid Earth and Natural Hazards Program, NASA Headquarters,
Washington.

“The quality of previous maps of the Earth varied
considerably, because they were compiled from various data
gathered by generations of explorers and surveyors. In some
places these maps are inaccurate. Using NASA technology, six
Space Shuttle astronauts mapped 80 percent of Earth’s land
surface in just 10 days to produce the first 3-D map of the
Earth’s surface at a known and uniform accuracy,” he said.

The need for accurate topographic maps is everywhere from
planning a hike to building a new highway. Knowing the exact
shape and location of mountain peaks and river valleys is as
important to the safe and efficient flight of aircraft as it
is to the management of water resources and the control of
forest fires.

Newly released images, representing the new SRTM30 data
products, depict Earth in two ways: as an image with all the
continents shown (a common map-making method known as a
Mercator projection); and as three globe images of Earth as
viewed from points in space centered over the Americas,
Africa and the western Pacific. Two visualization methods
were combined to produce the images: shading and color-
coding of topographic height. The shaded image was derived
by computing topographic slope in the northwest-southeast
direction, so northwest slopes appear bright and southeast
slopes appear dark. Color-coding depicts the lowest
elevations in green, rising through yellow and tan, to white
at the highest elevations.

The SRTM30 map is one of a series of land surface products
emerging from the very successful Shuttle Radar Topography
Mission (SRTM). SRTM has produced more detailed topographic
data for North and South America that resolves features
approximately 90 feet square, or 10 times the global SRTM30
database.

The SRTM data were processed at NASA’s Jet Propulsion
Laboratory, Pasadena, Calif., into research-quality digital
elevation data. NIMA is providing additional processing to
develop official mapping products. The U.S. Geological
Survey Earth Resources Observation Systems Data Center in
Sioux Falls, S.D. provides final archiving and distribution
of the SRTM data products.

The SRTM mission is a cooperative project of NASA, NIMA,
German and Italian space agencies. The project is part of
NASA’s mission to understand and protect our home planet.

The new images are available on the JPL Planetary
Photojournal at:

Information about the Shuttle Radar Topography Mission is
available at:

http://www.jpl.nasa.gov/srtm/

SpaceRef staff editor.