Hi!
I am using a Picam and a PiNOIR to take visible-light and infrared picture at the same time and create a NDVI picture using Warren photoshop tutorial but the results doesn't seems correct (the shadows appears produce a lot of photosynthesis).
Please could you confirm if that results are correct and if not what can I do to correct them?
infrared
NRG
NDVI
I tried to calibrate the IR following this post but the result is the same.
15 Comments
@Rayishido -the high NDVI values is a normal occurrence with shadows. You will notice that the NDVI values will change in the shadows depending on how light or dark the shadow is. I understand there is a method for correcting some of this in pre-processing however I have not attempted it myself. For me it is just an indicator that the area does not contain accurate values. If you can, try to take images at a different time of day when the shadows are not noticeable.
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Hi Rayishido,
Nice Pi photos. Claytonb is correct about the shadows. It's a common artifact for dark areas to have very high NDVI values. In your photos, the shadows in the NIR photo are not nearly as dark as in the VIS photo. So there is a big difference between NIR and VIS in the shadows and NDVI computes to very high values. Calibrating the process should improve the results.
The Photoshop process you used is quite tedious compared to using Ned Horning's plugin for Fiji. Below are results from Fiji.
Above: NDVI using the green channel from the NIR photo and the red channel from the VIS photo.
Above: NDVI using the red channel from the NIR photo and the red channel from the VIS photo.
Chris
The KAPtery
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