- edited description
What is the unit of reflectance and the number of bands of prisma product L2d?
Issue #1141
resolved
Dear Prisma users,
The number of bands of the Prisma L2d product is 234 and the reflectance of a pixel varies globally from 0 to 6000. Nevertheless, in several articles used this type of product, they quote that the number of bands of the Prisma product is 239 and the Reflectance values are usually displayed between 0 and 1.
- I know it's the PAN bands (5 bands), is there a setting to be made when downloading in order to have 239 bands in the L2d product?
- How to display the reflectance with values that vary between 0 and 1, is there a conversion to do?
Thank you in advance !
Comments (15)
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reporter
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How to display the reflectance with values that vary between 0 and 1, is there a conversion to do?
In v3.10, imported PRISMA data will be scaled between 0 and 1.
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I know it's the PAN bands (5 bands), is there a setting to be made when downloading in order to have 239 bands in the L2d product?
Please check the PRISMA website:
https://www.asi.it/en/earth-science/prisma/
And the documentation area (registration required) :
http://prisma.asi.it/missionselect/docs.php
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- changed status to resolved
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reporter
Thank you @Andreas Rabe for the documents you shared with me but unfortunately, I still haven't found an answer for my two questions:
- For the change in the magnitudes of the reflectance values from [0-1] to [0-7000/8000], in your opinion, this is due to the evolution of the Enmap-box version (v 3.1 to 3.9) or due to the evolution of the product (L1 to L2d) and therefore several corrections have been made by applying several equations. Ex. Equation 3 from Prisma manual. My final question, can we directly use the values of the reflectance of the pixels of the Prisma L2d product? we don't need to convert them to a scale [ 0 to 1] for example ???!!!
2. Once I have downloaded an L2d product in this way (see settings below), what is the number of the bands of the PAN (resolution at 5m) once displayed under Enmap-box?
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My final question, can we directly use the values of the reflectance of the pixels of the Prisma L2d product? we don't need to convert them to a scale [ 0 to 1] for example ???!!!
Depends on what you want to do. E.g. for some spectral indices like EVI, values need to be in the 0 to 1 range, otherwise the formular is not working correctly. For other indices like NDVI, a 0 to 10000 range is not a problem.
As mentioned, in the next version (v3.10), we always scale values to the 0 to 1 range.
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Once I have downloaded an L2d product in this way (see settings below), what is the number of the bands of the PAN (resolution at 5m) once displayed under Enmap-box?
PAN raster is always a single band raster.
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reporter
Thank you @Andreas Rabe for your explanations.
The current version of Enmap-box is 3.9, you want say a new version 3.91 or 4!!
Indeed, I will have to calculate the EVI index, according to you, is there an equation (article?) to apply and normalize the reflectance and have the values between 0 and 1 or else I can't do anything at the moment and I absolutely have to wait the release of the new version of Enmap-box?
How to download the raster PAN via the Prisma platform, I can't find the product in "Processing". Can you please give me a more specific answer? Thank you!!
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The current version of Enmap-box is 3.9, you want say a new version 3.91 or 4!!
No, the next version is 3.10.
(After 9 comes 10, right?
)
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Indeed, I will have to calculate the EVI index, according to you, is there an equation (article?) to apply and normalize the reflectance and have the values between 0 and 1
How do you want to calculate the EVI? With which tool/algorithm?
If you are using the QGIS, GDAL or EnMAP-Box raster calculators, you can just scale the data in the formular.
You don’t need a special formular fpr normalizing reflectance values. You just devide by 10000.
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How to download the raster PAN via the Prisma platform, I can't find the product in "Processing". Can you please give me a more specific answer? Thank you!!
The PAN band is inside the HE5 file. Unfortunately, in v3.9 we don’t unpack it for you. But you can do this in QGIS. When opening the HE5 file, QGIS shows this dialog, where you can select the PAN band here:
Note that in the upcoming v3.10, we will support all subdatasets of a PRISMA product:
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reporter
Ok thank you very much @Andreas Rabe for this additional explanation. I understand better now. Hoping that version 3.10 is coming very soon? Does it currently exist in an experimental version under QGIS?
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Hoping that version 3.10 is coming very soon?
Yes, already in test phase. Maybe 3 weeks.
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Does it currently exist in an experimental version under QGIS?
Yes, you can download it as experimental version in QGIS.
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reporter
Thank you very much!
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