Phantom 3 IR

[kique...@gmail.com]

I just bought a used Phantom 3 STD. I have a farm and I want to check through IR my plans NDVI.

I saw public lab sells an ir lens from a mobius. Also an it mobius.

I guess it's not that easy to buy the lens and try to make it work.

But what about buying the full mobius with ir filter and finding a way to attach it to the phantom?

Does the mobius has this setting to take a picture every few seconds?

Thank you.

[Chris Fastie]

Flying a Mobius ActionCam on a Phantom is a fine way to get aerial photos. It weighs only about 40 grams. The Mobius can be set to take photos at intervals of several seconds. You might want to build a mount that damps vibration. The IR modified Mobius sold by Public Lab takes photos which can be directly converted to a facsimile of NDVI. It is not very hard to put the IR converted lens on another Mobius camera. It is also fairly straightforward to put your own filter in any Mobius camera. 

Chris

[Enrique Duenas]

Thanks a lot!

Do you have any examples of a vibration dampening mount?

So if I understand okay, I can just take pictures with the Public Lab's mobius and then just put it on Infragram and will start to see some results?

Do you think I would get the same results from a Landsat satellite? We check the crops with the drone every 10 days.

What would you recommend?

[Ned Horning]

Hi Enrique,

If you search for "quadcopter vibration damping" you will see some innovative approaches for reducing vibration. For the Phantom 3 you should be able to find a way to attach a Mobius to the anti-vibration plate that holds the camera. That plate has four vibration dampeners - one in each corner.

Your NDVI results will be different from Landsat results for a few reasons. One is that you will see individual plant parts and Landsat will see 30m x 30m squares. Depending on how high you fly it is conceivable that a single photo would cover the same area as one or a few Landsat pixels. Due to that huge difference in spatial resolution you will see a lot of variation in your photos compared to Landsat. Landsat NDVI is also calibrated so different image (over space and time) can be compared. The Mobius images can be calibrated but I don't think that is possible using the online Infragram processing capabilities. You could try the FIJI plugin although that is experimental: https://publiclab.org/notes/nedhorning/01-13-2016/packaged-photo-monitoring-plugins-available-on-the-github-repositoy

Ensuring that your NDVI values are normalized to Landsat NDVI is not a trivial task but depending on what you are doing that might not be necessary. The Mobius NDVI is reasonably good at illustrating changes in plant health/vigor within a photo and often between photos of a single flight. Comparing photo acquired on different days requires a little more work but it's not difficult as long as the atmospheric (clouds and particulates) and sun conditions (time of day and time of year) are similar.

One word of caution is that there is a fairly long lag time (typically several days to well over a week) between when a plant is stressed and when that stress is evident using NDVI as an indicator of stress.

All the best,

Ned

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