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(Delta 1.0)) canopy-gap sizes were highly correlated (R-2 > 0.93) for 16 canopy gaps in the Cryptomeria japonica D. Don. plantations, and the relationship between A(Delta 1.0) and A(OBS) was expressed as A(Delta 1.0) = 1.16A(OBS). Thus, the method overestimated actual canopy-gap size by an average of 16%.