National Land Cover Database (NLCD) 2019 Products (ver. 3.0, February 2024)

The U.S. Geological Survey (USGS), in partnership with several federal agencies, has developed and released five National Land Cover Database (NLCD) products over the past two decades: NLCD 1992, 2001, 2006, 2011, and 2016. The 2016 release saw landcover created for additional years of 2003, 2008, and 2013. These products provide spatially explicit and reliable information on the Nation’s land cover and land cover change. To continue the legacy of NLCD and further establish a long-term monitoring capability for the Nation’s land resources, the USGS has designed a new generation of NLCD products named NLCD 2019. The NLCD 2019 design aims to provide innovative, consistent, and robust methodologies for production of a multi-temporal land cover and land cover change database from 2001 to 2019 at 2–3-year intervals. Comprehensive research was conducted and resulted in developed strategies for NLCD 2019: continued integration between impervious surface and all landcover products with impervious surface being directly mapped as developed classes in the landcover, a streamlined compositing process for assembling and preprocessing based on Landsat imagery and geospatial ancillary datasets; a multi-source integrated training data development and decision-tree based land cover classifications; a temporally, spectrally, and spatially integrated land cover change analysis strategy; a hierarchical theme-based post-classification and integration protocol for generating land cover and change products; a continuous fields biophysical parameters modeling method; and an automated scripted operational system for the NLCD 2019 production. The performance of the developed strategies and methods were tested in twenty composite referenced areas throughout the conterminous U.S. An overall accuracy assessment from the 2016 publication give a 91% overall landcover accuracy, with the developed classes also showing a 91% accuracy in overall developed. Results from this study confirm the robustness of this comprehensive and highly automated procedure for NLCD 2019 operational mapping. Questions about the NLCD 2019 land cover product can be directed to the NLCD 2019 land cover mapping team at USGS EROS, Sioux Falls, SD [phone] or [e-mail]. See included spatial metadata for more details.

美国地质调查局（U.S. Geological Survey, USGS）联合多家联邦机构，在过去二十年间研发并发布了五版全国土地覆盖数据库（National Land Cover Database, NLCD）产品，分别为NLCD 1992、2001、2006、2011与2016版。2016版还新增了2003、2008及2013三个年份的土地覆盖数据。该系列产品可为美国本土提供空间显性且可靠的土地覆盖及其变化信息。为延续NLCD的研究传统，并进一步建立美国土地资源的长期监测能力，美国地质调查局推出了新一代NLCD产品——NLCD 2019。NLCD 2019的设计目标是提供创新、一致且稳健的方法体系，以2至3年为时间间隔，生成2001年至2019年的多时相土地覆盖及土地覆盖变化数据库。本研究开展了全面的研发工作，形成了适配NLCD 2019的多项核心策略：一是将不透水面产品与全品类土地覆盖产品持续整合，将不透水面直接映射为土地覆盖中的开发用地类别；二是基于Landsat影像与地理空间辅助数据集，搭建标准化的合成预处理流程；三是开发多源融合的训练数据集，并采用基于决策树的土地覆盖分类方法；四是整合时间、光谱与空间维度的土地覆盖变化分析策略；五是构建基于分层主题的分类后集成协议，以生成土地覆盖与变化产品；六是研发连续场生物物理参数建模方法；七是搭建自动化脚本化的NLCD 2019业务化生产系统。所研发的策略与方法的性能，在美国本土全境的20个合成参考区域中完成了验证。根据2016年发布的研究成果，整体土地覆盖分类总体精度达91%，其中开发用地类别的总体精度同样为91%。本研究结果证实了该全面且高度自动化的NLCD 2019业务化制图流程的稳健性。若对NLCD 2019土地覆盖产品有疑问，可联系美国地质调查局地球资源观测与科学中心（EROS）的NLCD 2019制图团队，联系方式为：南达科他州苏福尔斯市，电话[phone]，或邮箱[e-mail]。更多细节请参阅随附的空间元数据（spatial metadata）。