One of the simplest, yet most visually revealing exercises to perform with TerraViva! Global Data Viewer is to view a selected area of the world using several different maps. The 3 images on the right are of a forested area in Rondonia, Brazil that has been clearcut in a deforestation pattern known as "fishbone." Notice the improved level of detail in the image on the left, generated with GlobCover from European Space Agency, a 300m (10 arc second) resolution dataset.

By right-clicking on any map we can perform a Quick Query of the underlying data. In this example we've opted to query the area within 10 kilometers of the point on the Earth located at -9.782/-63.660.

We'll query GlobCover and Global Land Cover 2000, however, Blue Marble is an image map and has no underlying data. It provides a good "true color" comparison.

Query results show show the number of pixels, the area, and the percent represented by each land cover type in the query area. Notice that the 8 GlobCover classifications shown here include fractional references within a type - a refinement that more accurately defines a type as a composite. This is an important trend in recent work with global land cover/land use datasets - providing fractional values on a scale from 0 to 1 to describe the content of a pixel, rather than assigning one flat categorical type based on the dominant land cover for the pixel.

The same Quick Query performed using map data from Global Land Cover 2000 (IES) produces a table with 6 land cover classifications.

What this exercise illustrates is that land cover data sets can differ greatly depending on the time period during which the data was acquired, the satellite and instrument used to gather the data, and the classifications used. Regardless, land use/land cover data provides a metric for measuring anthropogenic activity.