Wednesday, October 30, 2024

Government Information Resource: USGS (United States Geographical Survey) and the National Land Cover Database

According to its website, the USGS “monitors, analyzes, and predicts current and evolving Earth-system interactions and delivers actionable information at scales and timeframes relevant to decision-makers. [They] are a primary Federal source of science-based information on ecosystems, land use, energy and mineral resources, natural hazards, water use, and availability, and updated maps and images of the Earth’s features available to the public.”

The newest product released by the USGS is its updated and improved National Land Cover Database or Annual NLCD.  Unlike the previous version of the NLCD, which mapped land cover from 2001 to 2021 in two or three-year increments, the new version maps land cover from 1985 to the present in one-year increments.  It will be updated annually. 

The Annual NLCD contains six products:

1.       Land Cover – This dataset provides 16 land cover classes such as deciduous and evergreen forest, grassland, cultivated crops, and developed.

2.       Land Cover Change – These data represent annual land cover changes from one year to the next.

3.       Land Cover Confidence – This layer provides confidence levels for the land cover classifications.

4.       Fractional Impervious Surface – This component provides the proportion of land covered by developed surfaces, such as roads and rooftops.

5.       Impervious Descriptor – This feature offers additional information about impervious surfaces by distinguishing between roads and other built surfaces.

6.       Spectral Change Day of Year – This attribute captures the specific day of the year when significant changes in surface reflectance occur.

The Annual NLCD uses “the extensive Landsat satellite data record at a 30-meter resolution” and employs data from as far back as the early 1980s.  To ensure the accuracy and reliability of the data, the USGS meticulously reviews thousands of 30-meter plots and annually classifies and validates the data.

All of this data will be available to private individuals and companies, to members of the general public, and to academics and scholars.  The data may be used in various areas and for various interests, such as management and modeling of resources.  The data allows for assessing changes in the ecosystem, biodiversity, climate, surface and groundwater quality, wildlife, and other areas.  Wildfire threats, urban heat risks, and biological carbon sequestration can be modeled. These analyses provide more accurate and timely information for conservation efforts and land management. 

For more information on the Annual NLCD Collection 1.0, including how to access the data, visit the USGS website:https://www.usgs.gov/annualNLCD.