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Ray Arvidson

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  1. Hi Maeve: ENVI is the main way that researchers process CRISM data, including mapping mineral parameter maps. Do you have access to ENVI? And do you know which CRISM scenes you would like to use? I can tutor you through using ENVI and CRISM data, but first let me know if you have access to ENVI software. Ray Arvidson Geosciences Node Manager and CRISM Team Member.
  2. See attached paper, Section 5.3, for what we do for thresholds for parameter maps. Choosing a neutral spectrum is a case of trial and error. I do not do this, rather I just look at the volcano scanned spectra for features such as the 2.3 um metal-OH absorption. Ray Arvidson Viviano-Beck_et_al-2014-Journal_of_Geophysical_Research__Planets.pdf
  3. DISORT is a generally applicable radiative transfer program and is available over the internet. We use a front end that is Mars specific. It is incredibly complicated and not meant for distribution. May I suggest that unless you wish to do Hapke-related nonlinear modeling of mineral grain sizes and phases you just stick to what CAT offers. Except for our group very few researchers try and use DISORT in their CRISM data analysis. Ray Arvidson CRISM Team Member PDS Geosciences Node Manager
  4. The attached paper will show you how the library was created. Ray Arvidson Viviano-Beck_et_al-2014-Journal_of_Geophysical_Research__Planets.pdf
  5. Rochdi: Glad to have helped you along. Stay safe and healthy. Ray Arvidson
  6. Rochdi: I am not sure what you are asking. CAT has spectral parameters for IR data. Use this function. I am not trying to be judgmental. However, I suggest that you need to read in detail the Viviano-Beck paper that was sent to you and that you become very familiar with CAT and its functions. Many of your queries would have been answered if you had done this homework in detail. Ray Arvidson
  7. Yes, although the Viviano-Beck paper that we sent to you shows which bands to use for her indices. If you use your own indices and select accordingly. Ray Arvidson
  8. It should be a monochrome image with bright areas indicative of a high value for the spectral parameter used, yes. Ray Arvidson
  9. Result is one monochrome image. Do your band math in sensor space, use CAT to flatten the result, and then project. Results will have to be your task. I do not know where the pyroxene is located. Ray Arvidson
  10. Your band math seems to be missing parentheses at the appropriate places. Please read the band math documentation for how to represent algebraic expressions. Ray Arvidson
  11. Yes, for each pixel in the scene R2210 means use the reflectance value at 2210 nm. ENVI's Band Math function will allow you to write an equation that when run produces the parameter map.The tool is in the ENVI5 series interfaces on the right hand side under Band Algebra. Also, the weightings a, b, etc. in the equations allow centering of the computation over the deepest part of the putative absorption feature, all relative to the wavelengths on the continuum on either side of the feature. Ray Arvidson
  12. Yes, your results are what they should be, so congratulations. Ray Arvidson
  13. I suggest you look at the range of values in your cube. If there are extremely high excursions because of noise, or in L data, use of 65535 to indicate non-data, the system will scale its output relative to the extreme values and results will be black. Remove these values before proceeding. Ray
  14. Hi: I am here to help. Tell me what you mean by a 3D cube? Do you want a data cube where planes are images and each pixel has a spectrum associated with it? So when you display the S and L combined cube and use the spectral plot as you move around the image in the display the spectrum for that location shows in a plot window. Is that what you want? Build 3D cube does not do that and only produces a nice perspective view of the cube with an image on the top and color-coded spectral values down the side. https://www.l3harrisgeospatial.com/docs/ImageCubes.html Ray Arvidson Ah, I se
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