The National Land Cover Database (NLCD) is an operational land cover monitoring program providing updated land cover and related information for the United States at five-year intervals. NLCD2016 extends temporal coverage to 15 years (2001–2016). We collected land cover reference data for the 2011 and 2016 nominal dates to report land cover accuracy for the NLCD2016 database 2011 and 2016 land cover components at Level II and Level I and for Level I 2011–2016 land cover change using two definitions of agreement. For both the 2011 and 2016 land cover components, single-date Level II overall accuracies (OA) were 72% (standard error of ±0.9%) when agreement was defined as match between the map label and primary reference label only and 86% (± 0.7%) when agreement also included the alternate reference label. The corresponding level I OA for both dates were 79% (± 0.9%) and 91% (± 1.0%). The 2011–2016 user's and producer's accuracies (UA and PA) were ~ 75% for forest loss and PA for water loss, grassland loss, and grass gain were > 70% when agreement included a match between the map label and either the primary or alternate reference label. Depending on agreement definition and level of the classification hierarchy, OA for the 2011 land cover component of the NLCD2016 database was about 4% to 7% higher than OA for the 2011 land cover component of the NLCD2011 database, suggesting that the changes in mapping methodologies initiated for production of the NLCD2016 database have led to improved product quality. Additionally, we used the reference dataset collected for assessment of the NLCD2011 database to assess the 2001 and 2006 land cover components of the NLCD2016 database. OA for the 2001 and 2006 land cover components was 1% - 5% lower than OA for the 2011 and 2016 land cover components of the NLCD2016 database. Higher OA for 2011 and 2016 land cover components of the NLCD2016 database relative to OA for its 2001 and 2006 components may be attributable to differences in reference data quality.

国家土地覆盖数据库（NLCD）是一个可操作的土地覆盖监测程序，每五年提供一次美国的最新土地覆盖和相关信息。NLCD2016将时间范围扩展到15年（2001-2016年）。我们使用协议的两个定义，收集了2011年和2016年名义日期的土地覆盖参考数据，以报告NLCD2016数据库2011年和2016年的II和I级土地覆盖成分以及I-Level 2011-2016年土地覆盖变化的土地覆盖准确性。对于2011年和2016年的土地覆被组成部分，当协议被定义为仅地图标签和主要参考标签之间的匹配度时，单日II级总体准确度（OA）为72％（标准误为±0.9％）（86％） ±0.7％）时，协议还包括替代参考标签。两种日期的相应I OA分别为79％（±0.9％）和91％（±1.0％）。如果协议中包括地图标签与主要或次要指标之间的匹配，则2011-2016年使用者和生产者的森林损失准确率（UA和PA）为〜75％，水分损失，草地损失和草料收获的准确度为> 70％备用参考标签。根据协议定义和分类层次级别，NLCD2016数据库的2011年土地覆盖部分的OA比NLCD2011数据库的2011年土地覆盖部分的OA高约4％至7％，这表明映射方法的变化为生产NLCD2016数据库而发起的活动提高了产品质量。此外，我们使用收集的用于评估NLCD2011数据库的参考数据集来评估NLCD2016数据库的2001年和2006年土地覆盖成分。NLCD2016数据库中2001年和2006年土地覆盖成分的OA比2011年和2016年土地覆盖成分的OA低1％-5％。NLCD2016数据库的2011年和2016年OA相对于2001年和2006年OA而言，OA较高。这可能是由于参考数据质量不同所致。