National Land Cover Database
 The National Land Cover Database (NLCD) 2001 is a Landsat-derived, 30 meter spatial resolution digital land cover map that describes the land cover for the 50 U.S. states and Puerto Rico using twenty consistent land cover classes. The NLCD 2001 Alaska land cover classification will be the first to cover the entire state of Alaska at the 30 meter spatial resolution. Alaska Science Center geography staff have played a key role in the development of the NLCD 2001 Alaska product by completing early prototype land cover classifications and developing techniques to meet unique land cover mapping challenges in Alaska, organizing workshops to assist land cover mappers not based in Alaska, collecting an extensive database of field observations (including vegetation polygons and GPS-linked photographs), and providing evaluations for classifications in progress as well as quality control for the final land cover database.
After the completion and public release of the NLCD 2001 Alaska product, Alaska Science Center staff efforts will focus on completing an accuracy assessment for this product. The Alaska NLCD accuracy assessment strategy is a novel design that will maintain a statistically rigorous sampling scheme but also allow for adjustment of the sample size during the sampling process if unexpected difficulties such as poor weather, decreased funding, or other unexpected occurrences limit data collection in some areas of the state.
 A 2006 update to the NLCD 2001 Alaska product is also planned. This updated product will most likely follow similar protocols to those developed to update the NLCD 2001 CONUS product and will highlight large areas of significant land cover conversion (such as burns). The accuracy assessment design stratifies the state into seven primary regions (see figure at right) and 31 secondary regions that will be used as sampling strata. The design incorporates sampling blocks (blue squares in the image, 27 km2) randomly chosen from each of the 31 regions. Failure to sample within a given region due to insufficient funding, poor weather, or other limitations will redefine the sampling population but not affect the statistical validity of the overall sample.
Access and download Alaska NLCD here.
Principal Investigator: David Selkowitz (dselkowitz@usgs.gov, 907 786 7146)
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| NLCD 2001 Alaska Landsat imagery (left) and land cover classification (right) for the Talkeetna, Alaska area. | | Field data collection efforts for the NLCD 2001 Alaska campaign typically involved identification of vegetation types associated with clusters of Landsat pixels in remote areas of Alaska where little or no prior land cover data existed. |
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