Posted by
Christian Rixen on
Jun 02, 2009; 6:26pm
URL: http://imagej.273.s1.nabble.com/NDVI-analysis-tp3691320.html
Dear ImageJ community,
I have a question about NDVI analysis of photos of vegetation plots.
I would like to measure the NDVI as a measure for greenup of alpine
vegetation during the summer.
I have two digital cameras where the IR filter was removed
(CanonPowershotG10, IR Filter removed by the company LDP LLC,
www.maxmax.com). Then I have two filters, one for the visible light
(XNiteCC1-58) and one for the IR range (850 nm). I should be able to
get a reliable NDVI measurement by taking 4 pictures (visual plot, IR
plot, visual sky, IR sky) and calculating the NDVI according the the
equation NDVI= (NIR-VIS)/(NIR+VIS) (see method description on
http://www.iac.ethz.ch/staff/stockli/ndvimeasurement/ndvimeasurement.html).
I would of course use a manual exposure, I would not move the camera
between 2 shots and I would use a frame.
Now, here is my ImageJ question:
I want to get the red channel from my visible-light photo. Can I just
analyze the red channel of my picture with
Image -> color -> RGB split
and then measure the mean brightness of my red picture? And then I
could measure the brightness of my IR picture to obtain the brightness
values that I need for my NDVI equation?
I am a bit uncertain because I am not very familiar with image
analysis. What is the unit of the brightness value in ImageJ? Is the
value between 0 and 255 an official brightness value that I can use?
If yes, I would be set and could do my NDVI calculations.
Thanks to the community for your input.
Christian