I have canopy pictures taken with a Nikon 3100 with a fisheye converter lens. I would like to have canopy openness of it. Can anyone tell me how to do this?
Hi! scientists I am still looking for answer of this question? If someone has idea please?
Hi, if you are still interested, the manual of Frazer et al. 1997: "A method for estimating canopy openness, effective leaf area index, and photosynthetically active photon flux density using hemispherical photography and computerized image analysis techniques" might give you some insights.
Gap fraction is generally measured as the ratio of sky pixels (i.e. white pixels) to canopy pixels (i.e. black pixels) in a binarized canopy images. Canopy openness is a similar measure, but it weights pixels by zenith angle to account for distortion of different lens projections. So, for a hemispherical image with a polar projection, gap fraction and canopy openness should be equal.
A helpful reference:
Gonsamo, A., D’odorico, P., & Pellikka, P. (2013). Measuring fractional forest canopy element cover and openness - definitions and methodologies revisited. Oikos , 122(9), 1283–1291.
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