LANDSAT ORTHO ETM PLUS IMAGERY DATA SET ABSTRACT

Landsat Orthorectified ETM Plus Imagery Data Set Abstract

Introduction. 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 Landsat Enhanced Thematic Mapper Plus (ETM+) data set contains orthorectified ETM+ sensor data from the Landsat-7 satellite. Only the ETM+ images most closely meeting a specific set of criteria, including acquisition date, cloud percentage, data quality parameters, and best available phenology, were considered for the collection. The Landsat ETM+ data were provided by the USGS and orthorectified 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 8,500 Landsat ETM+ images were selected. These circa year 2000 scenes were acquired between 1999 and 2001, and have been orthorectified so as to tightly co-register with the earlier circa 1990 global Landsat TM coverage. NOTE: In both the circa 1990 and circa 2000 data sets, the temporal dates of individual scenes may vary between 1-3 years of the 1990/2000 baseline.) These images were either cloud-free or contained minimal cloud cover. In addition, only ETM+ 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 ETM+ data are orthorectified using existing orthorectified TM data as horizontal control. Pixel cross-correlation is used to pass the control from the earlier orthorectified TM data to the Landsat ETM+. A patented Landsat large block triangulation procedure is used to perform a photogrammetric adjustment of each individual Landsat ETM+ scene; data are then placed into a UTM / WGS84 map projection. All bands are individually re-sampled, using a nearest neighbor algorithm. The result is a final image map product with a Root Mean Square Error (RMSE) of better than 50 meters in positional accuracy.

For more information, see:

EarthSat's GeoCover Web Site

Contacts for Data Center/Data Access Information:

Customer Services

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.

Dykstra, Jon D., Jan/Feb 2001, The GeoCover-Ortho Program: Covering the Entire Earth's Landmass with 14,000 Landsat Images; GEO INFORMATICS, p. 26-29. Reference is available in PDF format.

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Document Review Date: December 22, 2003

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