I recall a message from Ecolog-L last year (https://listserv.umd.edu/cgi-bin/wa?A2=ind0508d&L=ecolog-l&F=&S=&P=3668) listing some software for hemispherical photography analysis. Here we have used both GLA and Hemiview with good results
The problem of threshold selection, and alternatives for automatic processing have been proposed in some recent articles, you may want to have a look ISHIDA M.(2004) Automatic thresholding for digital hemispherical photography. Canadian Journal of Forest Research: 34(11): 2208-2216. http://www.gifu-u.ac.jp/~ishidam/RGBFisheye02.htm Jonckheere, I., K. Nackaerts, B. Muys, and P. Coppin. 2005. Assessment of automatic gap fraction estimation of forests from digital hemispherical photography. Agricultural and Forest Meteorology 132:96-114. Nobis, M., and U. Hunziker. 2005. Automatic thresholding for hemispherical canopy-photographs based on edge detection. Agricultural and Forest Meteorology 128:243-250. Good luck! Francisco Rodriguez Sanchez Dept. Biologia Vegetal y Ecologia Universidad de Sevilla Apdo 1095, E-41080 Sevilla, SPAIN Phone: 954557056 e-mail: [EMAIL PROTECTED] http://www.alu.us.es/f/frodriguez -----Mensaje original----- De: Ecological Society of America: grants, jobs, news [mailto:[EMAIL PROTECTED] nombre de Sara Cairns Enviado el: viernes, 17 de marzo de 2006 16:36 Para: [email protected] Asunto: Re: [ECOLOG-L] Software for hemispherical photo analyses We've found GLA (free download from http://www.ecostudies.org/gla/) to be very useful. But we have not compared it to other programs. So we'll be interested in replies to this post. I'd like to add two specific questions: 1) I've had problems choosing a brightness threshold with GLA, using a slider bar (determining what is considered sky vs. vegetation). When I re-analyze the same photo (or someone else analyzes it), the variation due to differences in what threshold is choosen is large relative to the size of the effects we're trying to measure. Do other software programs have an option (e.g., an image categorization algorithm) that provides more consistency? What have other people's experiences been with this issue? 2) With GLA, batch processing is not an option. I can check the specs of other programs for this option (WinScanopy offers it), but wonder how well it works in practice. We want to measure light transmission and gap sizes for hundreds of hemispherical canopy photos. Thank you. - Sara Cairns [EMAIL PROTECTED] Data Manager / Biologist NH Natural Heritage Bureau Division of Forests & Lands (603) 271-2215 x 302 www.dred.state.nh.us/divisions/forestandlands/bureaus Date: Thu, 16 Mar 2006 17:44:19 -0600 From: Luben Dimov <[EMAIL PROTECTED]> Subject: Software for hemispherical photo analyses Dear All: Would anyone recommend me a good software package for analyses of hemispherical photographs? I see a copy of HemiView 2.1 lying around, but it seems rather old. Thanks, Luben [EMAIL PROTECTED]
