Biophysical Processor Landsat 8

Hi,

In the Help of SNAP 8.0, for Landsat 8, it is written that bands used as inputs are the blue, red, near_infrared, swir_1 and swir_2 in addition to the auxiliary bands (zenith and azimuth both for sun and view).


link: https://landsat.gsfc.nasa.gov/landsat-8/landsat-8-overview

In this case, band 2 is supposed to be used. However, if I create a subset including band 2 instead of band 3 and run the Biophysical Processor, I would get an error for missing band at 560.0nm.

For Landsat 8, the wavelength of Green band (band 3) is 560.0nm. It is contradictory to what is written in the Help. I am confused about this. Could someone help me?

image image

I don’t know what is correct, maybe @FlorianD clarify this?

But in the code those bands are required:
image

So green is needed instead of blue.
But @FlorianD needs to tell what is correct.

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Hi,
the help is wrong.
It must be the green band instead the blue band.
We will fix it.
Thanks for your feedback!
Best

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Thanks a lot!

Shixian

Thanks a lot

Shixian

@FlorianD, great. I think it would also be important to update the ATBD (http://step.esa.int/docs/extra/ATBD_S2ToolBox_L2B_V1.1.pdf) to explain the Landsat 8 (and S2 10m) option there as well.

Yes, I update with the new version. I check if the information of Landsat is correct.
I update the helper in the next release also.

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Hello, I used the Graph Builder to gain these bands from Landsat8 collection 2 level 1. But the error appeared too.
image
I was puzzled about it. Could someone help me?

Collection 2 is currently not supported in SNAP, can you please try Collection 1 products?

Hi,

I guess the problem is that you were using Landsat 8 Collection 2 data which is not currently supported by SNAP. In this case, metadata (for example, 560nm) cannot be loaded to the bands when you import them. I guess Biophysical Processor needs this information for recognizing specific bands.

I followed the steps below when using Landsat 8 images. Hope it will help you.

Steps:

  1. Download Landsat 8 Collection 1 Level 2 products. As the neural network was trained by the top of canopy reflectance, I guess we need BOA (bottom of the atmosphere) reflectance information.

  2. Download view angle files from Landsat 8 Collection 2 Level 1 products.

  3. Import the Landsat 8 Collection 1 Level 2 products into SNAP. (Be sure to import them using the XML file in the download product bundle)

  4. Import the view angle files.

  5. Apply Band Math to add view angle files as bands to the Landsat 8 Collection 1 Level 2 products. (Be aware that new band names should be: sun_zenith, sun_azimuth, view_zenith_mean, view_azimuth_mean)

  6. Subset the bands to your study area or directly run the Biophysical Processor.

Best,
Shixian

2 Likes

thank you for sharing your approach

My pleasure :grin:

Hi, I tried to obtain the fapar from a Landsat 8 image, following the insructions of Shixian, the result is not good, as it can be seen in the capture. I wonder if the reason for that strip effect shall be for the units or any another.

Hi,

The DN values of view angle images are scaled, did you divide it by 100?

The description can be found in Part A : https://prd-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/atoms/files/L8_AngleBands_README-20190503.txt

Best,
Shixian

1 Like

You´re right Shixian. That was my problem. Thanks a lot.