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- Title
Thermal canopy photography in forestry-an alternative to optical cover photography.
- Authors
NÖlke, Nils; Beckschäfer, Philip; Kleinn, Christoph
- Abstract
Hemispherical canopy photography is a widely used technique to observe crown-related forest variables. However, standardization of this technique remains challenging, as exposure and threshold settings continue to constitute the main sources of variation of such photographs. This paper presents a new method to overcome standardization issues by using thermal canopy photography. Using a thermal camera, images are produced which are not critically limited in their dynamic range so that photographic exposure becomes irrelevant. Moreover, the high temperature contrast between "sky" and "non-sky", resulting from extreme low sky temperatures, facilitates the unambiguous selection of a threshold which separates "sky" from "non-sky" pixels. For a comparison, we have taken canopy images with a high-resolution thermal camera (VarioCam hr head - Infratec, Dresden, Germany) and an optical camera (Nikon D70s). The correlation of canopy closure values derived from the image pairs was r = 0.98. Our findings thus show that thermal canopy photography is a promising and simple to use alternative to optical canopy photography, because it limits possible sources of variability, since exposure settings and threshold definition cease to be an issue.
- Subjects
HEMISPHERICAL photography; PHOTOGRAPHY archives; LEAF area index; PSEUDOMONAS aeruginosa; OSMOTIC pressure
- Publication
iForest - Biogeosciences & Forestry, 2015, Vol 8, Issue 1, p1
- ISSN
1971-7458
- Publication type
Article
- DOI
10.3832/ifor1129-007