Percent tree canopy cover in a ponderosa pine (Pinus ponderosa) forest of northeastern California was estimated by the point intercept spherical densiometer and ocular methods. Estimates derived by the two methods were similar (P > .05). The ocular method is recommended when understory vegetation is tall or clumped instead of randomly distributed, or if available field time limits sample size.
Vora, Robin S.
"A comparison of the spherical densiometer and ocular methods of estimating canopy cover,"
Great Basin Naturalist: Vol. 48
, Article 10.
Available at: http://scholarsarchive.byu.edu/gbn/vol48/iss2/10