Detecting plant disease by remote sensing

[Jazzscout]

Hi,

I want to develop a workflow to detect a specific disease in potato plants(potato blight) by remote sensing.

I have acquired the images of the potato field by mounting a multispectral camera on a drone that flew at an altitude of 5m above the plants.

The multispectral camera has 5 bands namely: Blue,Green,Red,NIR and RedEdge.

I have converted the DN(raw digital number) values of all bands in reflectance values and also applied lens correction and also aligned them.

I have first trained SVM(support vector machine) to segment soil from plants and then also applied SAVI(soil adjusted vegetation index) to refine soil segmentation from plants.

Now, I want to apply NDVI(normalized difference vegetation index) to determine the heath of plants pixel wise.

Is it the right approach to follow? Will NDVI be resonable to apply on images taken at just 5m height? Or is there any better approach?

Best regards...

[mamadouba]

It could be the correct approach, but it's basic or applied research that will take trial and error through scientific process.  There is no canned answer.  There are plenty of studies that support NDVI, or other vegetation indices (both narrow and broadband), serving as a proxy for crop health, vigor, LAI, etc.  Red edge has also shown promise in detecting the subtleties between a green, healthy plant and a relatively green, unhealthy plant.  The common denominator among these studies are field data; field data that has been collected in a meaningful and statistically rigorous manner so you can model the relationship between a vegetation index and the phenomenon of interest, in this case blight.  Have you collected ground truth data on plants with blight and plants without?  Can this be discerned at the spatial resolution that you are collecting at (5 meter overhead)?  If you find this out and can recommend optimal collection parameters and methods using UAS to detect blight, then I highly suggest that you publish your results.  

[Jazzscout]

So far, I have collected data on plants with blight(in a test field), but I will collect data on plants without blight in the coming season. And, yes if I find this out, I'll certainly publish my results. And I appreciate your response to my question. 

[rahmansunbeam]

I know one initiative who are doing similar project with Wageningen University. They have successfully done few similar work in Natherlands. This project is using Sentinel-2 image and combining that with local weather information to calculate late-blight disease vulnerability index. The project implements IDL and Python to automate the RS analysis. So far I know, this disease is highly dependent on moisture and temperature, and potato fields are relatively easy to identify from RS data.

We are doing something similar, but for paddy. There might be some algorithms already which you need to research.