National Land Cover Database (NLCD)
MRLC At-Sensor Reflectance Dataset Description
Multi-Resolution Land Characterization 2001 (MRLC 2001) is a second-generation federal consortium to create an updated pool of nation-wide Landsat imagery, and derive a second-generation National Land Cover Database (NLCD 2001).
One of the challenges to large-scale satellite based land cover characterization is consistent geometric correction and normalizing noise arising from atmospheric effect, changing illumination geometry, and instrument errors inherent when using multiple frames of imagery. For those reasons, we have created a product with additional processing from the Terrain Corrected scenes.
This product is designed for regional applications where scene mosaics can be substantially improved by converting DN to at-satellite reflectance to correct for Sun illumination angle effect. At-satellite reflectance images should be more appropriate for land cover and land cover change analysis than the original DN images. At-satellite reflectance also allows the development of a regionally applicable tasseled cap transformation using a physically based measurement. Overall, this method provides an important first-step to standardizing imagery, but users should realize that atmospheric, phenological and topographic noise do remain. Atmospheric correction is not considered as a standard step in MRLC image processing.
For details of MRLC preprocessing, please go to: http://www.mrlc.gov/pdf/image_processing.pdf
MRLC 2001 Landsat 7 data is currently available to all users. The data is to be used or disseminated with the intent of use for scientific purposes and only for a non-commercial venture.
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