Estimation of the canopy-gap size using two photographs taken at different heights

A new, convenient method to estimate canopy-gap size using a camera is proposed. Canopy-gap size was estimated from two images taken with a vertically mounted, digital camera at high and low points (P_h and P_l) beneath a canopy gap. The actual (A_OBS) and estimated (A_1.0) canopy-gap sizes were highly correlated (R² > 0.93) for 16 canopy gaps in the Cryptomeria japonica D. Don. plantations, and the relationship between A_1.0 and A_OBS was expressed as A_1.0 = 1.16A_OBS. Thus, the method overestimated actual canopy-gap size by an average of 16%.