National Land Cover Database 2001 (NLCD 2001)
Overview
The National Land Cover Database 2001 (NLCD 2001) is being compiled across all 50 states and Puerto Rico as a cooperative mapping effort of the MRLC 2001 Consortium. This land cover database is being created using mapping zones (download zones here) and contains standardized land cover components useful for a variety of applications. NLCD 2001 is scheduled for completion on or before December 31, 2006. As mapping zones are completed, they are made available on the MRLC 2001 website Dynamic Download tool.
Main Components
- Independent DEM ancillary data layers of slope, aspect, elevation and topographic position.
- Classified Land Cover data derived from imagery and ancillary data using a Decision Tree.
- View and Download NLCD 2001 Land Cover data (MRLC Interactive Viewer)
- View NLCD 2001 Land Cover Class Definitions
- View Land Cover partner map
- Independent per-pixel estimates of Imperviousness and Tree Canopy derived from imagery and ancillary data using a Regression Tree
Methodology
The development of NLCD 2001 methodology was carefully planned to offer users a full range of flexible applications. The overall database philosophy and methodology is presented in Homer et al - (Download Adobe Acrobat Reader). Specific major improvements in methodology and their accompanying research support documentation include:
- Identification of optimal early, peak and late Landsat TM scene acquisitions for each path/row based on AVHRR seasonal averages. (Yang et al)
- Development of Landsat 7 radiometric and at-sensor reflectance calibrations for imagery to reduce mosaicing difficulty. (Huang et al)
- Development of Tasseled Cap coefficients for Landsat 7 at-sensor reflectance (Huang et al)
- Justification of Tasseled Cap as an optimal way of distilling 6 bands into 3 (Wylie et al)
- Regional mapping using land cover friendly mapping zones (Homer et al, and Figure A) (Download ARC-INFO Mapping Zone File)
- Development of imperviousness estimates from TM imagery. (Yang et al)
- Development of tree canopy estimates from TM imagery. (Huang et al)
- Development of image processing rules coupled with ancillary data as needed to classify Landsat data into land cover. (Figure B)
- Comprehensive accuracy assessments of the land cover data and related components.
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