In this method for canopy cover measurement a sampling unit of the smallest possible dimension (point) is considered and whether vegetation intercepts this point is recorded. Percentage of points intercepted by vegetation gives estimates of total canopy cover.
Some instruments that are used to make more precise recordings:
Spherical Densiometer: It comprises of a mirror (concave or convex). The surface area of this mirror is engraved in grid with equal area squares. The projected canopy cover can be calculated based on number of these squares covered by the canopy. More information about spherical densiometer can be found here.
Cajanus tube: It is simple handheld tube-like instrument with mirror. It is used to look up vertically and record whether the exact point above is covered by the canopy. More information about cajanus tube can be found here.
Point-Frames: these are frames with grid of sharpened pins or cross-hairs marked by lines that grid the surface of frames. These are used for surveying herbaceous vegetation. The pins are lowered and number of pins that hit the plant surface are recorded. More information about point-frames can be found here.