Landsat Orthorectified TM Imagery Data Set Abstract
Background. Data were compiled through NASA's Commercial Remote
Sensing Program; this program is a cooperative effort between NASA and the
commercial remote sensing community to provide users with access to
quality-screened, high-resolution satellite images with global coverage over
the Earth's land masses. The resulting EarthSat thematic mapper (TM) geocover
data set contains orthorectified Landsat TM sensor data from the Landsat-4
and -5 satellites. Only the Landsat images that most closely met a specific
set of criteria, including acquisition date, cloud percentage, data quality
parameters, and best available phenology, were considered for the collection.
The Landsat TM data were compiled through a NASA contract with Earth
Satellite Corporation, Rockville, Maryland, and are part of NASA's Scientific
Data Purchase program, developed in response to the President's Space
Policy.
Data Set Characteristics. Approximately 7,461 Landsat TM images were
selected. The acquisition dates of these images were relative to a 1990
acquisition baseline, and the images were either cloud-free or contained
minimal cloud cover. In addition, only TM images with a high quality ranking
in regards to the possible presence of errors such as missing scans or
saturated bands were selected. It was important to collect data during
periods of peak greenness so NASA adopted an approach for image selection
that was based upon a data set containing global 1-kilometer advanced very
high-resolution radiometer Normalized Difference Vegetation Index data. It
was sometimes difficult for NASA to obtain clear images during time frames of
peak greenness, resulting in some image substitution from other times of the
year.
Processing. Landsat images were orthorectified, using geodetic and
elevation control data to correct for positional accuracy and relief
displacement. Large blocks of Landsat data were adjusted through a patented
procedure that uses pixel correlation to acquire tie-points within the
overlap area between adjacent Landsat images. Ground control points are
fixed, and images are projected to the Universal Transverse Mercator map
projection, using the World Geodetic System 1984 datum. All bands are
individually resampled, using a nearest neighbor algorithm. The result is a
final product with a Root Mean Square Error of better than 50 meters in
positional accuracy.
For more information, see:
Contacts for Data Center/Data Access Information:
References:
Kalluri, Satya, Grant, Denelle, Tucker, Compton, Policelli, Fritz, Dykstra,
Jon, and Bearden, Phil, 2000, NASA creates global archive of ortho-rectified
Landsat data: EOS, Transactions, American Geophysical Union, v. 81, no. 50,
p. 609, 617-618.
Disclaimer: Any use of trade, product, or firm names is for descriptive
purposes only and does not imply endorsement by the U.S. Government.
Document Review Date: July 24, 2000
