Thematic Accuracy Assessment of the NLCD 2016 land cover for the conterminous United States
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. NLCD 2016 extends temporal coverage to 15 years (2001 – 2016). Accuracy assessment of NLCD land cover products has been an established standard of practice. We report land cover accuracy for NLCD 2016 database for the conterminous United States. Accuracy estimates were calculated for the 2001, 2006, 2011, and 2016 land cover components at Level II and Level I of the classification hierarchy using two definitions of agreement, and for 2011 – 2016 land cover change at Level I. For both the 2011 and 2016 components, single-date Level II overall accuracies (OA) were 72% (± 0.9%) when agreement was defined as match between the map label and primary reference label only and 87% (± 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%). OA for the 2011 and 2016 components of the NLCD 2016 database were 1% - 5% higher than OA for the 2001 and 2006 components of the NLCD 2016 database depending on agreement definition and the level of the classification hierarchy. Consistent with previous NLCD accuracy assessments, 2011 – 2016 only user’s accuracies urban gain and forest loss were ≥ 70%, but producer’s accuracies for all loss and gain themes showed considerable improvement over those from previous assessments. OA for the 2011 land cover component of the NLCD 2016 database was about 4% to 7% higher than OA for the 2011 land cover component of the NLCD 2011 database depending on agreement definition and level of the classification hierarchy, suggesting that the changes in mapping methodologies initiated for production of the NLCD 2016 database have led to improved product quality. Higher OA values for the 2011 and 2016 land cover components than the 2001 and 2006 land cover components suggest that improved reference data quality may have also contributed to improved accuracies for the NLCD 2016 database.