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Detection & Imagery

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Hi Arno,

I'm just wondering, with your detection feature, does that use all 4 bands to calculate or does it just calculate:

(B4-B1) / (B4+B1)

i.e. RGBI (4 band imagery)

If it's just (B4-B1) / (B4+B1) then would it be possible to add a calculation option of:

(B1-B2) / (B1+B2)

i.e. IRG (3 band CIR Imagery)

Key:
R = Red
G = Green
B = Blue
I = (Near) Infra Red
 
Hi Dean,

At the moment it assumes the nir is in the fourth band. Would be a good idea to make that adjustable.
 
Hi,

I have added an option now in the NDVI filter so that you can select the band for the red and NIR data.
 
Hi Arno,

I'm not having any joy with the test CIR imagery I'm using I selected the NirBand=0 and RedBand=1 (this is on CIR imagery with band0 Nir, Band1=red, Band2=green

Even though I'm seeing the correct NDVI values as I hover over the image, I don't seem to be getting any tree detections or polygons being generated.

Would it be worth me sending over some samples?

Cheers,
Dean.

EDIT: I just grabbed my RGB imagery and added the NIR band to it to create a 4 band image and the NDVI filter worked correctly on it, so something appears to possibly be amiss with the calculations, I can send over the samples for you :D
 
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Hi,

If you have a sample with different bands I'll try to test it.
 
Will do, I'll send it over after I get some sleep. :) One thing I'm wondering is if the formula might have been reversed.

4 Band RGBI = (B4 - B1) / (B4 + B1)
3 Band CIR = (B1 - B2) / (B1 + B2)

I'm wondering perhaps if when changing the bands for CIR to NIR = 0, Red = 1 whether the formula might be doing:

(B2 - B1) / (B2 + B1)

I might quickly test that out actually... Standby...

Edit: Nope it's not that...
 
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Hi Dean,

I found the issue. It was due to the empty (or non-existing) 4th band. This results in pixels with a value of 255 and a standard deviation of 0 because they are all the same. And my minimum and maximum value checks were not inclusive of the checked value, so that's why the pixels were not matched. I'll put a fixed version online in a few minutes.
 
Arno, thank you so much, can't wait to try it out :D Will be a very interesting test exercise :D You might just cause me to re-design and re-write my whole development process with this :)

Edit, tested it out, Works great, now to remember what I do for the second stage lol. Time to go back and read the "manual" :D
 
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The sample image you send me to debug was very good. For Nantucket the NIR imagery is not that good. That makes vegetation detection much more reliable.
 
Oh cool :) . I was doing research the other day and I think I'm going to have a lot of fun in time generating datasets with this tool. :) I'll let you know how it goes :)
 
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