LCMAP Collection 1 Science Products - Annual Land Cover Change
An overview of LCMAP Collection 1 Science Products: Annual Land Cover Change
LCMAP Collection 1 science products include 10 data sets offering different perspectives for the study of land change across the country, through time. While the Annual Land Cover Change product looks very similar to the Primary Land Cover product it contains additional data allowing users to easily identify annual land cover changes. Both products identiy 8 land cover classes, represented by unique colors and numeric values 1 through 8. The change product, however, includes additional values to indicate where land cover change has occured, rendered as purple.
Land cover change for a given year is synthesized from the Primary Land Cover product by comparing land class values to those of the previous year. In this example, many pixel values did not change between 2013 and 2014. The pixels that did change, appear as purple in the Annual Land Cover Change product. But annual change does not happen uniformly. These pixels changed from Tree Cover to Barren. These pixels changed from Tree Cover to Grass/Shrub, and these pixels changed from Grass/Shrub to Barren. To distinguish these changes, each purple pixel is represented in the data product as a two digit value, representing the previous land cover class, and the current. While some change value combinations are more common than others, they can range from 12 to 87, representing the full set of class change possibilities, and they all display as purple in the product.
Here's a real world example to better visualize how one year of land cover change data is synthesized from two years of Primary Land Cover product data. Note the colors and values in areas where change is observed versus areas where change is not observed. In another example, different class changes are shown but the technique for encoding land cover change data into a single product, is the same.
While the Annual Land Cover Change product can be useful in studying land cover change, it's important to note that not all changes are identified. When certain conditional changes occur, they may not trigger a shift in land cover class. For example, a thinning forest may be classify as Tree Cover for many years despite a reduction in tree density. In addition, the Land Cover Change product does not indicate the specific activities causing change over time. A change from Tree Cover to Grass/Shrub may be due to harvest, disease, insect outbreak, fire, weather, or a number of other circumstances. Users interested in investigating the cause of change should utilize additional data sources.
LCMAP Collection 1 science products can be accessed through Earth Explorer or the LCMAP Web Viewer. More in-depth information on all LCMAP science products can be found on the LCMAP website.