Canopy cover [Crown cover]
n. The fraction of ground area covered by the vertical projection of tree crown perimeters.
Canopy cover is commonly expressed as a percentage of total ground area; for example, at 50 percent canopy cover, half of the total ground area is covered by the vertical projection of tree crowns.
Unless otherwise specified, canopy cover refers to non-overlapping canopy cover. Two overlapping crowns are not counted twice, so the theoretical maximum attainable canopy cover value is 100 percent. Values of overlapping canopy cover, used in ecological applications, can exceed 100 percent.
Canopy cover is not synonymous with canopy closure, which is a point measure of canopy coverage.