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How get images with surface reflectance value
3319 8 2023-7-19
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Terra Drone
lvl.1
Chile
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Hi!
How is it possible to generate images with the surface reflectance data?
Currently, I don't know what is delivered in actual images is a DN (Digital number) or another, the issue is that if I want to apply other indices that they do not exist in DJI Terra, it's not possible for me, because the image that is generated does not have these reflectance values (or I don't know how generate or extract).

I would like to know how to obtain an image with surface reflectance value or if not, please that option could be implemented in the future.

Attached graphic that shows the reflectance values for the terrestrial surface, the issue is that my Mavic 3 Multispectral images, the pixel value gives me, for example: 0-2000 for green and 0-2726 for NIR, this in one place with water and vegetation.


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2023-7-19
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DJI Wanda
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About your questions, reflectivity = solar irradiance/reflection intensity.
The concept of radiometric correction is introduced to obtain the solar irradiance (radiant luminance) in the operation environment. The main principles and steps are as follows: Use a standard calibration board with known reflectivity. Take a photo in the operation environment facing towards the calibration board. As the reflectivity and the photo’s reflection intensity are known, we can now ascertain the solar irradiance in the environment. After obtaining the solar irradiance in the environment, plug it into each plant photo during operation to calculate the reflectivity of each photo so as to obtain the NDVI index.
According to your combination - DJI Mavic 3M + DJI Terra, we will recommend you one solution:
1) Use the fusion value of several sensors (camera and the spectral sunlight sensor on top of the aircraft) to obtain the reflectivity, so as to calculate the NDVI and other indices.
While performing reconstruction with DJI Mavic 3M photos, DJI Terra will obtain the reflectivity based on the camera’s DN value (reflection intensity) and the solar irradiance obtained by the spectral sunlight sensor, and then calculate the NDVI and other indices. DJI’s solution is to make a real-time radiometric correction. Use DJI Terra to build index diagrams requiring no radiometric correction or reflectivity. With this method, relatively uniform reflectivity values can be obtained at different times to output a relatively correct index diagram.
The advantages of this method: Radiometric correction is not required before an operation. The data accuracy will not be impacted by weather. This method is applicable to more weather conditions with wider operation scopes.
2023-7-19
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Terra Drone
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Chile
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DJI Wanda Posted at 7-19 22:54
About your questions, reflectivity = solar irradiance/reflection intensity.
The concept of radiometric correction is introduced to obtain the solar irradiance (radiant luminance) in the operation environment. The main principles and steps are as follows: Use a standard calibration board with known reflectivity. Take a photo in the operation environment facing towards the calibration board. As the reflectivity and the photo’s reflection intensity are known, we can now ascertain the solar irradiance in the environment. After obtaining the solar irradiance in the environment, plug it into each plant photo during operation to calculate the reflectivity of each photo so as to obtain the NDVI index.
According to your combination - DJI Mavic 3M + DJI Terra, we will recommend you one solution:

I really tried to find the way to "Use the fusion value of several sensors (camera and the spectral sunlight sensor on top of the aircraft) to obtain the reflectivity" and I can't find where to configure that neither in DJI Terra nor in the drone same, please attach a picture of where exactly I set that up or any clue to replicate it.

I would like to know how to obtain this data and thus not work with DN but with the reflectance value to apply other indices and experiment with the mix of bands, but having the physical variable of the electromagnetic spectrum and not a DN value.
2023-7-31
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DJI Wanda
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Terra Drone Posted at 7-31 10:45
I really tried to find the way to "Use the fusion value of several sensors (camera and the spectral sunlight sensor on top of the aircraft) to obtain the reflectivity" and I can't find where to configure that neither in DJI Terra nor in the drone same, please attach a picture of where exactly I set that up or any clue to replicate it.

I would like to know how to obtain this data and thus not work with DN but with the reflectance value to apply other indices and experiment with the mix of bands, but having the physical variable of the electromagnetic spectrum and not a DN value.

The image taken by DJI Mavic 3M is  DN value.
You can see the tuorials here:
https://www.dji.com/dji-terra/info#video
2023-8-1
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VBio
lvl.2
Flight distance : 2122598 ft

Indonesia
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once I ever get copy of image sample from M3M. I used to process with Pix4D for multi-spectral analysis. in step 3, there is an option to show reflectance number each band, so I assume this number is reflectance because this number also use in the formulae to produce other indices i.e. NDVI, NDRE etc.
2023-10-16
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fans5f2117ac
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Hungary
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VBio Posted at 2023-10-16 00:24
once I ever get copy of image sample from M3M. I used to process with Pix4D for multi-spectral analysis. in step 3, there is an option to show reflectance number each band, so I assume this number is reflectance because this number also use in the formulae to produce other indices i.e. NDVI, NDRE etc.

Hello,

is there a chance to get reflectance value for each image by using Pix4D as you mentioned? If yes, could you give a screen shoot where to find it?
2024-2-4
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VBio
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Flight distance : 2122598 ft

Indonesia
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fans5f2117ac Posted at 2-4 03:57
Hello,

is there a chance to get reflectance value for each image by using Pix4D as you mentioned? If yes, could you give a screen shoot where to find it?

in step 3 you can generate each layer of the band started from green, red, nir, rededge
2024-7-3
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202Optics
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United States
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what are the specifications of the built in solar iridescence sensor?
1-30 16:56
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DJI Paladin
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Flight distance : 318 ft

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202Optics Posted at 1-30 16:56
what are the specifications of the built in solar iridescence sensor?

Hello there. Thank you for reaching out. Please provide the model of device so we can check it further. We will wait for your response. We appreciate your cooperation.
1-31 01:50
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