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Ausiàs R

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About Ausiàs R

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  1. I'm sorry, I don't know what that area can be or how can I get it. Nevertheless thanks for your help. Ausiàs.
  2. Hi Ray, First of all I want to thank for your reply, it is really apreciated. You said that: I understand that the area that looks like it and is spectrally neutral means an area that exhibes a constant reflectivity or transmissivity over the electromagnetic spectrum. But, where can I find this kind of surface/area? Is the data that I need on the ddr files of the image? I saw that there are 14 bands on the ddr images. On this document (pages 76-77) it is explained what those bands represents. I'm not pretty sure which band I shoud use, or if any. Once again, thanks for your answer, Ausiàs.
  3. Good afternoon. I'm an undergraduate student of geomatics and remote sensing, and I was trying to use the CRISM images to classify minerals and chemical compounds on the surface of Mars. I collected some information about all the products to use, also I followed the workflow proposed here and I installed CAT on ENVI. I was trying to use a an image of the Jezero Crater data product: frt00005c5e_07_if166j_mtr3, which is projected, atmosferically and geometrically corrected. The data is on I/F which as is explained here, on the FAQs means: Q: What does I/F stand for? A: CRISM is a reflectance spectrometer, and I/F is how reflectance is represented algebraically: I is the energy (actually radiance) observed by the CRISM instrument, and F is the energy (actually solar irradiance) incident at the top of the Martian atmosphere. I/F is a ratio of energies (radiance/irradiance), with some additional scaling so the ratio is unitless. Acording to my knowledge radiance/irradiance=reflectance (unitless), maybe I'm wrong. The case is that I tried to classify the minerals on the image of the Jezero Crater using this library from Viviano et al using the "CRISM RATIOED I/F CORRECTED" spectra but I get wrong or absurd results. I noticed that the spectra of my images is clearly different from the spectra that I find on the Viviano library ratioed i/f. My Spectra always follow this pattern, and never reaches a reflectance of 0.5. Nevertheless on the Viviano library I found spectra like this one of epidote: Why the spectra of my image is so different? Is my data really on reflectance? How can I get real reflectances?
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