Hi, On 06/16/2014 07:47 PM, Brian Matherly wrote: >> NDVI = (IR - VIS) / (IR + VIS) > > What is the equation for VIS? "VIS = (G + B) / 2" ?
No, usually the infrablue filters don't let any green pass, so in this case, VIS would be the blue channel and IR the red channel. > Are negative NDVI values "rounded" to zero? No, they appear. I would have to read up on the details, but I believe that the result is treated as signed byte, i.e. the center of the greyscale equals NDVI value of 0, Maximal brightness 1 and minimal brightness -1. I'm not so good at explaining but maybe this GIMP tutorial can shed some light on that :). http://publiclab.org/notes/warren/10-27-2011/video-tutorial-creating-false-color-ndvi-aerial-wetlands-imagery > I've noticed that some people prefer a mapping that colors vegetation > green. But that wouldn't be a standardized NDVI image then :). > I doubt the frei0r heat map will do that. If someone goes through > the trouble of making a filter for NDVI, it probably wouldn't be that > hard to make a custom color map while they are at it. That is way beyond my coding skills, so I can't comment on that. But of course, I would assume that the possibility to change some settings would be useful. >> Would anybody be interested in implementing it? > > I don't personally have any interest, but I could always be persuaded :) Well, considering the current boom in personal environmentalism (see publiclab.org), the citizen drone movements (see diydrones.com), and the combination of both (see conservationdrones.org) you would not only be my personal hero but also the hero of at least half of the 54000 DIY-Drones members (I would of course write a post about that there :) ) plus Linux (KDEnLive, Shortcut, etc.) would be the first platform which can create NDVI videos in a single rather simple step by just applying one filter in an editor :). -S -- (o_ Stefan Gofferje | SCLT, MCP, CCSA //\ Reg'd Linux User #247167 | VCP #2263 V_/_ Heckler & Koch - the original point and click interface
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