The gap fraction technique is at present the most powerful and practical tool available for indirect sensing of canopy structure. It can be applied not only to continuous canopies, but also to discrete foliage-containing envelopes, such as row structure or individual trees.
Canopy structure information, including amount and orientation of foliage, can be estimated from measurements of gap fractions.
The gap fraction of a canopy is the fraction of view in some direction from beneath a canopy that is not blocked by foliage. The fractional sunfleck area is equivalent to the gap fraction in the solar direction.