Question: NDVI Numerical Values

AgtechMan asked on September 28, 2018 08:43
96 views | 2 answers | #17184


Hi, I'd like to purchase the Waterproof Mini Camera (infrared-ready). Will this be suitable for indoor hydroponics farms? Also how do I get the NDVI numerical values? I need the numbers in order to create a data model to predict growth.

Cheers



5 Comments

Hi, and welcome to Public Lab! I don't know if anyone has used this for hydroponics before, but i bet someone will be able to tell you about your ndvi question. Thanks for asking!

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the Waterproof Mini Camera (infrared-ready)

Be aware that this camera must be opened and modified before it can capture near infrared light. The product description at the Public Lab Store is quite easy to misinterpret. I could find no information about converting this particular model, and regardless, the product description says that the model may vary.

Will this be suitable for indoor hydroponics farms?

The standard interpretation of NDVI values assumes that the photos were taken with the plant foliage illuminated by sunlight. If your plants are illuminated with artificial lights or sunlight filtered through modern windows, the ratio of NIR to visible light could differ enough to make NDVI meaningless.

Also how do I get the NDVI numerical values?

The Photo Monitoring Plugin for Fiji will produce a grayscale image (single channel) with the NDVI values for each pixel encoded in each pixel. Fiji allows manipulating these values, e.g., the mean value within a polygon can be displayed interactively. Fiji allows scripting.

Chris

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Hi! Image Sequencer's NDVI module now has a "hover to see NDVI values" feature:

https://publiclab.org/image-sequencer (see "Activities")

Try this demo for example

Also, here are a lot of previous posts about hydroponics.

https://publiclab.org/search/hydroponics

I think it may be good to consider using a more configurable camera like the Raspberry Pi camera, where you can set the camera settings very precisely. This may result in better data:

#pi-camera

Thanks guys. Really helpful responses. Looks like Pi Noir camera v2 is my best bet at the moment. For the lighting I'll be using a set of full spectrum LED grow lights (PPFD: >130 µmol/m2/s at 15cm). I'd be glad to share my experience as I progress. Recommendations are highly welcomed.

Cheers


I am not sure what "full spectrum" means when used to describe LEDs. It probably means that all the visible wavelengths are present in the light at more or less the same intensity. It probably does not mean that near infrared light is present. NIR is not used by plants and does not help them grow, so grow lights would be wasting energy producing NIR. So if your LED grow lights are the only illumination, there will probably be no NIR impacting or reflecting from the foliage and a plant health measure like NDVI will have no meaning at all. In order to get meaningful NDVI results you will probably have to add a source of NIR light. This could be about half as bright as the red part of the visible illumination to mimic the red:NIR ratio in sunlight. The camera will not be as sensitive to NIR as it is to red light, so making the NIR source very bright can help exaggerate the brightness of NIR so your NDVI values are similar to legacy (e.g., satellite) NDVI.

Chris


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