Public Lab Research note


Accessible Vegetation Indices.

by gpenzo | December 11, 2014 12:45 | 2,899 views | 4 comments | #11448 | 2,899 views | 4 comments | #11448 11 Dec 12:45

Read more: unstable.publiclab.org/n/11448


What I want to do

I want to get Vegetation Indices, like NDVI, WDVI, NDRE ,EVI I want to make a cape for a beaglebone black which will hold 2 or more cmos cameras to capture diffrent wave lenght for each camera.

I have been seaching for days for a cheap camera that has good response from 600nm till 800 nm. And I found it.

Camerea wavelenght response wave_length_response.png

Camerea monochrome wavelenght response

wave_length_mono_response.png

Resolution is not that high 752*480. But I want to use it for earial imaging. I do not need 12MP images of a piece of farmland too get an idea how the land is doing this is good enough. Can always make allot of pictures and stich them together. Looking at the wavelenght response two of these cameras will make very good NDVI, WDVI images.

I also want to try NDRE and EVI. But these indices require a smaller band than NDVI. This can be a problem becuase less light will get to the sensor. Looking at the spectral response you can see that both blue and red have the same response at 850nm. I presume that all the pixel have the same respons only they are covered with color filters. I have two solutions. 1. Use monochrome on each camera 2. Remove the Color filter array from these cameras like the astro guys and see If I can use all the pixels for 600nm too 850nm.

CFA removal

My attempt and results

Both cameras are working. But is looks like I have some fixed patern noise. After long testing and measuring I think that these sensors are not good or the camera pc has not enough of digitaal and analog power filtering.

Visible light Only IR cut filter. I should use a red band filter but that is for later.

vis_Clipped.jpg

IR cut filter removed and used 720 IR filter.

ir.JPG

NDVI

vis_NDVI_Color.jpg

Questions and next steps

Try the new sensors to see If I can remove the interference, If everything work as it should, I will order my pcb for the cape. I want the cameras to have a cs mount so diffrent lenses can be tried and better qality. All kind of cs mount lenses can be bought online for cheap. And I want to make a web interface on the beaglebone for configuring this.

Why I'm interested

If have made NDVI pictures with to canon cameras (search my notes). I do not find it user friendly, to much steps that can go wrong. I want the image processing to be automatically, overlay on google maps etc. This needs to be more accessible. Especially farmers that I know do not want to mess arround with hardware it just needs to work. I want to make something more lighter for my drone. Need to get 20-25 minutes fligth.

Regards Grayson Penzo

Test1.JPG

First PCB design without lens

pcb_v1.JPG


4 Comments

First result. Allot of work to go.

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Hi gpenzo

From Colombia...

I would like to know how I can get the filter for such cameras to build a camera in order to obtain the index PRI.

Thank You

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More info see another note: http://publiclab.org/notes/gpenzo/03-25-2015/ndvi-cape-for-the-beagle-bone

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Hallo John. Based on wikipedia you need 531 and 570 nm filters. I checked arround and I could not find those filters. I saw 540nm and 580nm http://www.edmundoptics.com/optics/optical-filters/bandpass-filters/visible-bandpass-interference-filters/3429/ I suggest you google arrond for band filters and see what you can get. What kind of cameras you want to use? If you want to use two consumer cameras look arround on this site for ndvi setup. Or check my profile I used two canon cameras. If you need anymore info let me know.

Grayson.

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