Excess Green Index

I am using a standard Phantom 4 proV2 to take pictures of potato crops here in Tasmania.

I am using WebODM running on Ubuntu18.04 updated to latest version to create my orthophotos. It works faultlessly and I really like the new plant health options such as VARI.

Another index I am using to extract more of the variation in the green potato canopy is the Excess Green Index.

I use the Raster Calculator in QGIS to produce this index (2*Green)-(Red+Blue). I display the image as pseudo color ranging from red through yellow to green.

Is it possible to add this index to list ?

To give an example of how I am displaying the Excess Green index have a look at this image.
Carr Ranson 79DAP ExGr 15cm

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That would be a great addition. Would you be interested in opening a pull request by editing https://github.com/OpenDroneMap/WebODM/blob/master/app/api/formulas.py ?

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Thanks for the opportunity. I had a look at the link but I have done no programming so don’t understand what you mean by a pull request.

Using your VARI formula
‘VARI’: {
‘expr’: ‘(G - R) / (G + R - B)’,
‘help’: ‘Visual Atmospheric Resistance Index shows the areas of vegetation.’,
‘range’: (-1, 1)
},

This what ExGr should look like

‘ExcessGreen’: {
‘expr’: '(2*G)-(R+B),
‘help’: ‘Excess Green Index emphasizes the greenness of leafy crops such as potatoes.’,
‘range’: (-50,150)
},

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No worries, it’s pretty simple, no programming skills required:

  1. Register an account on GitHub.
  2. Edit the file via this link: https://github.com/OpenDroneMap/WebODM/edit/master/app/api/formulas.py
  3. Press the green button at the bottom of the page, adding a description of what was changed.
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OK I’ll give it a go.

Is there a way I can test it on my copy of WebODM ?

You can if you setup a development environment. https://docs.webodm.org/#for-developers

Done as you suggested.

Like you said it was self explanatory and not very hard.

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Just updated my copy of WebODM and checked out the added EXG index.

It worked like a charm and gave the same view as I expected.

The next thing I thought of was the ability to trim the orthophoto to the field boundary.

Any ideas ?

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There is a cutline option in processing options for exactly this.