The United States Geological Survey (USGS) Land Cover Trends field photography collection is a national-scale, ground-reference dataset which initially served as a research tool to aid in Landsat-derived land-use/land-cover (LULC) change analyses and assessments. Between 1999 and 2007, Land Cover Trends scientists collected over 33,000 geographically referenced field photos with associated keywords capturing existing LULC and regional change process taking place. The field photography collection represents the most comprehensive national database of geo-referenced USGS field photography in the United States. In a project funded by the USGS Climate and Land Use Change and Core Science Systems Mission Areas, 18,000 photos distributed across 56 Level III Environmental Protection Agency (EPA) ecoregions are currently being disseminated to the public. As the remaining field photographs are geotagged, the online collection will grow to include photos within 28 additional ecoregions.
Integrating Land Cover Trends field photography and online mapping technology provides access to new and archived USGS geographic data needed to conduct science and support policy decisions. Sharing this unique field photography provides an excellent resource for the scientific community with potential to develop future research, such as future repeat photography projects or applications where photos may serve as training or test site data for other remote sensing classifications. Serving USGS data interactively to the public is integral to the USGS mission and provides opportunities for future scientific collaboration by communicating USGS land change research to the broader public and scientific community.
For information how to use the map interface, please refer to the “How to use viewer” section of the website.
Researchers with the USGS Land Cover Trends Project created a dataset for the conterminous United States designed to characterize the historical state of the nation's land surface between 1973 and 2000. The dataset was created developed using a statistical sampling approach because it was a much more cost efficient method for characterizing LULC change over as large an area as the United States. Ecological regions were used as a geographic framework for selecting sample blocks across the United States with a total of 2,688 sample blocks randomly selected from 84 Level III ecoregions. Researchers manually interpreted Landsat MSS, TM and ETM+ imagery for five dates (1973, 1980, 1986, 1992, and 2000) and then used the land cover data to derive change statistics for each interval (1973-1980, 1980-1986, 1986-1992, and 1992-2000) and for the entire study period (1973-2000), ultimately serving as the basis for ecoregion-based change estimates used as the primary land-change metrics in reporting. The viewer above allows the user to view sample blocks and ecoregions alongside field photographs use to aid in the interpretation of LULC from Landsat imagery.
Change estimates are used to determine: (1) the predominant types of LULC conversions occurring within each ecoregion, (2) the estimated rates of change for these conversions, and (3) whether the types and rates of change are constant or variable across time. The analysis of change, which was conducted in several ecoregion publications, also involved looking for spatial correlations between conversion types and selected environmental factors, such as terrain characteristics, proximity to urban development, economic conditions, et cetera, in order to improve our understanding of potential drivers of change. Publications and sample block interpretations can be accessed at the Land Cover Trends Website.