Getting Started - What are Landcover Data?

Concepts:
   landcover
   imperviousness
   classes

Landcover data are spatial data which indicate, for a particular area, the type of dominant vegetation or man-made landscape.  Typically, these categories are divided into landcover 'classes'.  The group of classes is referred to as the landcover 'classification' for the layer.  An example of a landcover class is "Deciduous Forest" or "High-intensity Developed".  Imperviousness data are related to landcover data, and indicate for a particular area whether or not water may pass through into the ground.  Some imperviousness classifications are based on percentages (i.e. an area is 50% impervious) while others may be a simple yes/no (i.e. the area is impervious).

 
Landcover of the Bangor area at the mouth of Kenduskeag Stream.  Legend shows the classification from MELCD 2004 data, subset just for this area.

 
Two examples of imperviousness data, MELCD 2004 (left) which is a simple yes/no classification at a 5m resolution, and NLCD 2001 (right) with classes of impervious in 10% increments at a 30m resolution.  The former has better spatial resolution, the latter has better thematic resolution (more about that in section 2).